ADD: Normal mapping

Readme.md

@@ -6,7 +6,7 @@ Work-In-Progress Vulkan render engine
 Current structure:
 - Flexible render graph system with multiple render passes
 - Deferred rendering
-- PBR(IBL is WIP), shadow, 
+- PBR (IBL is WIP), cascaded shadows, normal mapping (MikkTSpace tangents optional)
 - GLTF loading and rendering, primitive creation and rendering.
 
 Work-In-Progress

docs/ASSETS.md

@@ -20,4 +20,8 @@
 
 - Materials & sRGB
   - See `docs/asset_manager.md` for mesh/material creation and sRGB/UNORM handling.
+  - Conventions:
+    - Albedo/base color → sRGB
+    - Metallic-Roughness → UNORM (G=roughness, B=metallic)
+    - Normal map → UNORM (+Y green up)
 

docs/BUILD.md

@@ -32,6 +32,11 @@
 - Third‑party deps
   - Vendored under `third_party/` and brought in via CMake. Do not edit headers directly; update through targets.
 
+- Optional: MikkTSpace tangents
+  - Enable at configure time: `-DENABLE_MIKKTS=ON` (default ON if found).
+  - Requires `third_party/MikkTSpace/mikktspace.c` and `mikktspace.h` (provided).
+  - Disable to use the built‑in Gram–Schmidt generator: `-DENABLE_MIKKTS=OFF`.
+
 - Validation Layers
   - Enabled in Debug (`kUseValidationLayers = true` in `src/core/config.h`).
   - Disable by building Release or toggling the flag during local experimentation.

docs/SHADERS.md

@@ -18,6 +18,12 @@
   - Name SPIR‑V files with full extension, e.g. `fullscreen.vert.spv`, `deferred_lighting.frag.spv`.
   - Use `EngineContext::getAssets()->shaderPath("<name>.spv")` when registering pipelines.
   - Use sRGB formats for albedo textures and UNORM for PBR control textures (see `docs/asset_manager.md`).
+  - Material UBO layout (`GLTFMaterialData`):
+    - `vec4 colorFactors;`
+    - `vec4 metal_rough_factors; // x = metallic, y = roughness`
+    - `vec4 extra[14];            // extra[0].x = normalScale`
+  - Material texture bindings (set=1):
+    - binding=1 `colorTex`, binding=2 `metalRoughTex`, binding=3 `normalMap`.
 
 - Adding a pipeline (graphics)
   - Fill `GraphicsPipelineCreateInfo` with shader paths, descriptor set layouts, optional push constants, and a `configure(PipelineBuilder&)` callback to set topology, raster, depth/blend, and attachment formats.

docs/TROUBLESHOOTING.md

@@ -24,3 +24,13 @@
   - Confirm the `.spv` file changed (timestamp) and click “Reload Changed” in the Pipelines window.
   - Ensure you are editing the correct files referenced by `shaderPath()`.
 
+- GLSL error: `no such field in structure 'materialData': extra`
+  - Ensure `shaders/input_structures.glsl` defines `vec4 extra[14];` inside `GLTFMaterialData` to match C++ `MaterialConstants`.
+
+- Normals look inverted when using normal maps
+  - The engine expects +Y (green up) tangent-space normals. Flip the green channel in your texture if needed.
+
+- Tangent seams or artifacts
+  - Build with MikkTSpace enabled: `-DENABLE_MIKKTS=ON`.
+  - Check that your mesh has non-degenerate UVs.
+

docs/asset_manager.md

@@ -40,9 +40,11 @@ Use either the convenience descriptor (`MeshCreateInfo`) or the direct overload
 struct AssetManager::MaterialOptions {
   std::string albedoPath;        // resolved through AssetManager
   std::string metalRoughPath;    // resolved through AssetManager
+  std::string normalPath;        // resolved through AssetManager (tangent-space normal)
   bool albedoSRGB      = true;   // VK_FORMAT_R8G8B8A8_SRGB when true
   bool metalRoughSRGB  = false;  // VK_FORMAT_R8G8B8A8_UNORM when false
-  GLTFMetallic_Roughness::MaterialConstants constants{};
+  bool normalSRGB      = false;  // normal maps should be UNORM
+  GLTFMetallic_Roughness::MaterialConstants constants{}; // extra[0].x as normalScale
   MaterialPass pass    = MaterialPass::MainColor; // or Transparent
 };
 
@@ -113,7 +115,7 @@ ctx->scene->addMeshInstance("sphere.instance", sphere,
     glm::translate(glm::mat4(1.f), glm::vec3(2.f, 0.f, -2.f)));
 ```
 
-Textured primitive (albedo + metal-rough):
+Textured primitive (albedo + metal-rough + normal):
 
 ```c++
 AssetManager::MeshCreateInfo ti{};
@@ -124,7 +126,9 @@ ti.geometry.vertices = std::span<Vertex>(v.data(), v.size());
 ti.geometry.indices  = std::span<uint32_t>(i.data(), i.size());
 ti.material.kind = AssetManager::MeshMaterialDesc::Kind::Textured;
 ti.material.options.albedoPath = "textures/ground_albedo.png";     // sRGB
-ti.material.options.metalRoughPath = "textures/ground_mr.png";     // UNORM
+ti.material.options.metalRoughPath = "textures/ground_mr.png";     // UNORM, G=roughness, B=metallic
+ti.material.options.normalPath     = "textures/ground_n.png";      // UNORM
+ti.material.options.constants.extra[0].x = 1.0f;                    // normalScale
 // ti.material.options.pass = MaterialPass::Transparent; // optional
 
 auto texturedPlane = ctx->getAssets()->createMesh(ti);
@@ -156,4 +160,5 @@ ctx->scene->removeGLTFInstance("chair01");
 - Reuse by name: `createMesh("name", ...)` returns the cached mesh if it already exists. Use a unique name or call `removeMesh(name)` to replace.
 - sRGB/UNORM: Albedo is sRGB by default, metal-rough is UNORM by default. Adjust via `MaterialOptions`.
 - Hot reload: Shaders are resolved via `shaderPath()`; pipeline hot reload is handled by the pipeline manager, not the AssetManager.
-- Normal maps: Not wired into the default GLTF PBR material in this branch. Adding them would require descriptor and shader updates.
+- Normal maps: Supported. If `normalPath` is empty, a flat normal is used.
+- Tangents: Loaded from glTF when present; otherwise generated. Enable MikkTSpace at configure time with `-DENABLE_MIKKTS=ON`.

docs/materials.md

@@ -0,0 +1,43 @@
+Materials and Textures Overview (PBR)
+
+Current state (as of Nov 1, 2025)
+- PBR textures bound per material (set=1):
+  - binding=0: GLTFMaterialData (UBO)
+  - binding=1: `colorTex` (albedo/base color) — sRGB
+  - binding=2: `metalRoughTex` (G=roughness, B=metallic) — UNORM
+  - binding=3: `normalMap` (tangent-space normal, UNORM)
+- G‑Buffer writes world‑space normals. Tangent‑space normal maps are decoded with TBN using a sign‑correct bitangent (B = sign * cross(N, T)).
+- Numeric fallbacks via `MaterialConstants` (CPU) / `GLTFMaterialData` (GPU):
+  - `colorFactors` (RGBA). Defaults to 1 if zero.
+  - `metal_rough_factors` (X=metallic, Y=roughness). Roughness is clamped to ≥ 0.04 in shaders.
+  - `extra[0].x` = `normalScale` (scalar, default 1.0). Multiplies the XY of decoded normal.
+- Defaults when a texture is missing:
+  - Albedo → checkerboard error texture
+  - MR → white (no effect)
+  - Normal → 1×1 flat normal (0.5, 0.5, 1.0)
+
+Implications for primitive meshes
+- Primitives can use:
+  - Albedo + MR + Normal textures, or
+  - Numeric factors only, or
+  - Any mix (missing textures fall back to defaults).
+
+Texture conventions
+- Albedo/base color: sRGB.
+- Metallic-Roughness: UNORM; channels: G=roughness, B=metallic.
+- Normal map: UNORM; expected +Y (green up). If your maps look inverted, flip the green channel offline.
+
+Notes on tangent space
+- Tangents are loaded from glTF when present (`TANGENT` attribute, vec4 where w is handedness).
+- If missing, the engine generates tangents:
+  - Default: robust Gram–Schmidt with handedness.
+  - Preferred: MikkTSpace (enabled by CMake option `ENABLE_MIKKTS=ON`).
+
+Notes on MikkTSpace
+- Recommended for parity with content tools. Enable at configure time: `-DENABLE_MIKKTS=ON`.
+- Falls back automatically to the internal generator if disabled or if MikkTS fails.
+
+Usage Examples
+- Adjust normal strength per material: set `material.constants.extra[0].x` (CPU) or `normalTexture.scale` in glTF.
+- Primitive with PBR textures:
+  - Set `MeshMaterialDesc::Kind::Textured` and fill `albedoPath`, `metalRoughPath`, and `normalPath`.

shaders/gbuffer.frag

@@ -6,6 +6,7 @@ layout(location = 0) in vec3 inNormal;
 layout(location = 1) in vec3 inColor;
 layout(location = 2) in vec2 inUV;
 layout(location = 3) in vec3 inWorldPos;
+layout(location = 4) in vec4 inTangent;
 
 layout(location = 0) out vec4 outPos;
 layout(location = 1) out vec4 outNorm;
@@ -20,7 +21,17 @@ void main() {
     float roughness = clamp(mrTex.x * materialData.metal_rough_factors.y, 0.04, 1.0);
     float metallic  = clamp(mrTex.y * materialData.metal_rough_factors.x, 0.0, 1.0);
 
+    // Normal mapping: decode tangent-space normal and transform to world space
+    // Expect UNORM normal map (not sRGB). Flat fallback is (0.5, 0.5, 1.0).
+    vec3 Nm = texture(normalMap, inUV).xyz * 2.0 - 1.0;
+    float normalScale = max(materialData.extra[0].x, 0.0);
+    Nm.xy *= normalScale;
+    vec3 N = normalize(inNormal);
+    vec3 T = normalize(inTangent.xyz);
+    vec3 B = normalize(cross(N, T)) * inTangent.w;
+    vec3 Nw = normalize(T * Nm.x + B * Nm.y + N * Nm.z);
+
     outPos = vec4(inWorldPos, 1.0);
-    outNorm = vec4(normalize(inNormal), roughness);
+    outNorm = vec4(Nw, roughness);
     outAlbedo = vec4(albedo, metallic);
 }

shaders/input_structures.glsl

@@ -28,8 +28,10 @@ layout(set = 1, binding = 0) uniform GLTFMaterialData{
 
     vec4 colorFactors;
     vec4 metal_rough_factors;
+    vec4 extra[14];
 
 } materialData;
 
 layout(set = 1, binding = 1) uniform sampler2D colorTex;
 layout(set = 1, binding = 2) uniform sampler2D metalRoughTex;
+layout(set = 1, binding = 3) uniform sampler2D normalMap; // tangent-space normal, UNORM

shaders/mesh.frag

@@ -7,6 +7,7 @@ layout (location = 0) in vec3 inNormal;
 layout (location = 1) in vec3 inColor;
 layout (location = 2) in vec2 inUV;
 layout (location = 3) in vec3 inWorldPos;
+layout (location = 4) in vec4 inTangent;
 
 layout (location = 0) out vec4 outFragColor;
 
@@ -57,7 +58,14 @@ void main()
     float roughness = clamp(mrTex.x * materialData.metal_rough_factors.y, 0.04, 1.0);
     float metallic  = clamp(mrTex.y * materialData.metal_rough_factors.x, 0.0, 1.0);
 
-    vec3 N = normalize(inNormal);
+    // Normal mapping path for forward/transparent pipeline
+    vec3 Nm = texture(normalMap, inUV).xyz * 2.0 - 1.0;
+    float normalScale = max(materialData.extra[0].x, 0.0);
+    Nm.xy *= normalScale;
+    vec3 Nn = normalize(inNormal);
+    vec3 T = normalize(inTangent.xyz);
+    vec3 B = normalize(cross(Nn, T)) * inTangent.w;
+    vec3 N = normalize(T * Nm.x + B * Nm.y + Nn * Nm.z);
     vec3 camPos = vec3(inverse(sceneData.view)[3]);
     vec3 V = normalize(camPos - inWorldPos);
     vec3 L = normalize(-sceneData.sunlightDirection.xyz);

shaders/mesh.vert

@@ -9,6 +9,7 @@ layout (location = 0) out vec3 outNormal;
 layout (location = 1) out vec3 outColor;
 layout (location = 2) out vec2 outUV;
 layout (location = 3) out vec3 outWorldPos;
+layout (location = 4) out vec4 outTangent; // xyz: world tangent, w: sign
 
 struct Vertex {
 
@@ -17,6 +18,7 @@ struct Vertex {
     vec3 normal;
     float uv_y;
     vec4 color;
+    vec4 tangent;
 };
 
 layout(buffer_reference, std430) readonly buffer VertexBuffer{
@@ -38,6 +40,8 @@ void main()
     gl_Position = sceneData.viewproj * worldPos;
 
     outNormal = (PushConstants.render_matrix * vec4(v.normal, 0.f)).xyz;
+    vec3 worldTangent = (PushConstants.render_matrix * vec4(v.tangent.xyz, 0.f)).xyz;
+    outTangent = vec4(normalize(worldTangent), v.tangent.w);
     // Pass pure vertex color; apply baseColorFactor only in fragment
     outColor = v.color.xyz;
     outUV.x = v.uv_x;

shaders/shadow.vert

@@ -9,6 +9,7 @@ struct Vertex {
     vec3 position; float uv_x;
     vec3 normal;   float uv_y;
     vec4 color;
+    vec4 tangent;
 };
 
 layout(buffer_reference, std430) readonly buffer VertexBuffer{

src/CMakeLists.txt

@@ -72,6 +72,8 @@ add_executable (vulkan_engine
   scene/vk_scene.cpp
   scene/vk_loader.h
   scene/vk_loader.cpp
+  scene/tangent_space.h
+  scene/tangent_space.cpp
   scene/camera.h
   scene/camera.cpp
   # compute
@@ -89,7 +91,13 @@ target_include_directories(vulkan_engine PUBLIC
   "${CMAKE_CURRENT_SOURCE_DIR}/compute"
 )
 
+option(ENABLE_MIKKTS "Use MikkTSpace for tangent generation" ON)
+
 target_link_libraries(vulkan_engine PUBLIC vma glm Vulkan::Vulkan fmt::fmt stb_image SDL2::SDL2 vkbootstrap imgui fastgltf::fastgltf)
+if (ENABLE_MIKKTS)
+  target_link_libraries(vulkan_engine PUBLIC mikktspace)
+  target_compile_definitions(vulkan_engine PUBLIC MIKKTS_ENABLE=1)
+endif()
 
 add_library(vma_impl OBJECT vma_impl.cpp)
 target_include_directories(vma_impl PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/../third_party/vma")

src/core/asset_manager.cpp

@@ -7,6 +7,7 @@
 #include <core/vk_resource.h>
 #include <render/vk_materials.h>
 #include <render/primitives.h>
+#include <scene/tangent_space.h>
 #include <stb_image.h>
 #include "asset_locator.h"
 
@@ -142,6 +143,12 @@ std::shared_ptr<MeshAsset> AssetManager::createMesh(const MeshCreateInfo &info)
             break;
     }
 
+    // Ensure tangents exist for primitives (and provided geometry if needed)
+    if (!tmpVerts.empty() && !tmpInds.empty())
+    {
+        geom::generate_tangents(tmpVerts, tmpInds);
+    }
+
     if (info.material.kind == MeshMaterialDesc::Kind::Default)
     {
         return createMesh(info.name, vertsSpan, indsSpan, {});
@@ -151,9 +158,11 @@ std::shared_ptr<MeshAsset> AssetManager::createMesh(const MeshCreateInfo &info)
 
     auto [albedo, createdAlbedo] = loadImageFromAsset(opt.albedoPath, opt.albedoSRGB);
     auto [mr, createdMR] = loadImageFromAsset(opt.metalRoughPath, opt.metalRoughSRGB);
+    auto [normal, createdNormal] = loadImageFromAsset(opt.normalPath, opt.normalSRGB);
 
     const AllocatedImage &albedoRef = createdAlbedo ? albedo : _engine->_errorCheckerboardImage;
     const AllocatedImage &mrRef = createdMR ? mr : _engine->_whiteImage;
+    const AllocatedImage &normRef = createdNormal ? normal : _engine->_flatNormalImage;
 
     AllocatedBuffer matBuffer = createMaterialBufferWithConstants(opt.constants);
 
@@ -162,6 +171,8 @@ std::shared_ptr<MeshAsset> AssetManager::createMesh(const MeshCreateInfo &info)
     res.colorSampler = _engine->_samplerManager->defaultLinear();
     res.metalRoughImage = mrRef;
     res.metalRoughSampler = _engine->_samplerManager->defaultLinear();
+    res.normalImage = normRef;
+    res.normalSampler = _engine->_samplerManager->defaultLinear();
     res.dataBuffer = matBuffer.buffer;
     res.dataBufferOffset = 0;
 
@@ -171,6 +182,7 @@ std::shared_ptr<MeshAsset> AssetManager::createMesh(const MeshCreateInfo &info)
     _meshMaterialBuffers.emplace(info.name, matBuffer);
     if (createdAlbedo) _meshOwnedImages[info.name].push_back(albedo);
     if (createdMR) _meshOwnedImages[info.name].push_back(mr);
+    if (createdNormal) _meshOwnedImages[info.name].push_back(normal);
     return mesh;
 }
 
@@ -213,6 +225,10 @@ AllocatedBuffer AssetManager::createMaterialBufferWithConstants(
     {
         matConstants->colorFactors = glm::vec4(1.0f);
     }
+    if (matConstants->extra[0].x == 0.0f)
+    {
+        matConstants->extra[0].x = 1.0f; // normal scale default
+    }
     // Ensure writes are visible on non-coherent memory
     vmaFlushAllocation(_engine->_deviceManager->allocator(), matBuffer.allocation, 0,
                        sizeof(GLTFMetallic_Roughness::MaterialConstants));
@@ -270,6 +286,8 @@ std::shared_ptr<MeshAsset> AssetManager::createMesh(const std::string &name,
         matResources.colorSampler = _engine->_samplerManager->defaultLinear();
         matResources.metalRoughImage = _engine->_whiteImage;
         matResources.metalRoughSampler = _engine->_samplerManager->defaultLinear();
+        matResources.normalImage = _engine->_flatNormalImage;
+        matResources.normalSampler = _engine->_samplerManager->defaultLinear();
 
         AllocatedBuffer matBuffer = createMaterialBufferWithConstants({});
         matResources.dataBuffer = matBuffer.buffer;

src/core/asset_manager.h

@@ -25,9 +25,13 @@ public:
     {
         std::string albedoPath;
         std::string metalRoughPath;
+        // Optional tangent-space normal map for PBR (placeholder; not wired yet)
+        // When enabled later, this will be sampled in shaders and requires tangents.
+        std::string normalPath;
 
         bool albedoSRGB = true;
         bool metalRoughSRGB = false;
+        bool normalSRGB = false; // normal maps are typically non-sRGB
 
         GLTFMetallic_Roughness::MaterialConstants constants{};
 

src/core/vk_engine.cpp

@@ -51,6 +51,268 @@
 #include "core/vk_pipeline_manager.h"
 #include "core/config.h"
 
+//
+// ImGui helpers: keep UI code tidy and grouped in small functions.
+// These render inside a single consolidated Debug window using tab items.
+//
+namespace {
+    // Background / compute playground
+    static void ui_background(VulkanEngine *eng)
+    {
+        if (!eng || !eng->_renderPassManager) return;
+        auto *background_pass = eng->_renderPassManager->getPass<BackgroundPass>();
+        if (!background_pass) { ImGui::TextUnformatted("Background pass not available"); return; }
+
+        ComputeEffect &selected = background_pass->_backgroundEffects[background_pass->_currentEffect];
+
+        ImGui::Text("Selected effect: %s", selected.name);
+        ImGui::SliderInt("Effect Index", &background_pass->_currentEffect, 0,
+                         (int)background_pass->_backgroundEffects.size() - 1);
+        ImGui::InputFloat4("data1", reinterpret_cast<float *>(&selected.data.data1));
+        ImGui::InputFloat4("data2", reinterpret_cast<float *>(&selected.data.data2));
+        ImGui::InputFloat4("data3", reinterpret_cast<float *>(&selected.data.data3));
+        ImGui::InputFloat4("data4", reinterpret_cast<float *>(&selected.data.data4));
+
+        ImGui::Separator();
+        ImGui::SliderFloat("Render Scale", &eng->renderScale, 0.3f, 1.f);
+    }
+
+    // Quick stats & targets overview
+    static void ui_overview(VulkanEngine *eng)
+    {
+        if (!eng) return;
+        ImGui::Text("frametime %.2f ms", eng->stats.frametime);
+        ImGui::Text("draw time %.2f ms", eng->stats.mesh_draw_time);
+        ImGui::Text("update time %.2f ms", eng->_sceneManager->stats.scene_update_time);
+        ImGui::Text("triangles %i", eng->stats.triangle_count);
+        ImGui::Text("draws %i", eng->stats.drawcall_count);
+
+        ImGui::Separator();
+        ImGui::Text("Draw extent: %ux%u", eng->_drawExtent.width, eng->_drawExtent.height);
+        auto scExt = eng->_swapchainManager->swapchainExtent();
+        ImGui::Text("Swapchain:   %ux%u", scExt.width, scExt.height);
+        ImGui::Text("Draw fmt:    %s", string_VkFormat(eng->_swapchainManager->drawImage().imageFormat));
+        ImGui::Text("Swap fmt:    %s", string_VkFormat(eng->_swapchainManager->swapchainImageFormat()));
+    }
+
+    // Shadows / Ray Query controls
+    static void ui_shadows(VulkanEngine *eng)
+    {
+        if (!eng) return;
+        const bool rq = eng->_deviceManager->supportsRayQuery();
+        const bool as = eng->_deviceManager->supportsAccelerationStructure();
+        ImGui::Text("RayQuery: %s", rq ? "supported" : "not available");
+        ImGui::Text("AccelStruct: %s", as ? "supported" : "not available");
+        ImGui::Separator();
+
+        auto &ss = eng->_context->shadowSettings;
+        int mode = static_cast<int>(ss.mode);
+        ImGui::TextUnformatted("Shadow Mode");
+        ImGui::RadioButton("Clipmap only", &mode, 0); ImGui::SameLine();
+        ImGui::RadioButton("Clipmap + RT", &mode, 1); ImGui::SameLine();
+        ImGui::RadioButton("RT only", &mode, 2);
+        if (!(rq && as) && mode != 0) mode = 0; // guard for unsupported HW
+        ss.mode = static_cast<uint32_t>(mode);
+        ss.hybridRayQueryEnabled = (ss.mode != 0);
+
+        ImGui::BeginDisabled(ss.mode != 1u);
+        ImGui::TextUnformatted("Cascades using ray assist:");
+        for (int i = 0; i < 4; ++i)
+        {
+            bool on = (ss.hybridRayCascadesMask >> i) & 1u;
+            std::string label = std::string("C") + std::to_string(i);
+            if (ImGui::Checkbox(label.c_str(), &on))
+            {
+                if (on) ss.hybridRayCascadesMask |= (1u << i);
+                else    ss.hybridRayCascadesMask &= ~(1u << i);
+            }
+            if (i != 3) ImGui::SameLine();
+        }
+        ImGui::SliderFloat("N·L threshold", &ss.hybridRayNoLThreshold, 0.0f, 1.0f, "%.2f");
+        ImGui::EndDisabled();
+
+        ImGui::Separator();
+        ImGui::TextWrapped("Clipmap only: raster PCF+RPDB. Clipmap+RT: PCF assisted by ray query at low N·L. RT only: skip shadow maps and use ray tests only.");
+    }
+
+    // Render Graph inspection (passes, images, buffers)
+    static void ui_render_graph(VulkanEngine *eng)
+    {
+        if (!eng || !eng->_renderGraph) { ImGui::TextUnformatted("RenderGraph not available"); return; }
+        auto &graph = *eng->_renderGraph;
+
+        std::vector<RenderGraph::RGDebugPassInfo> passInfos;
+        graph.debug_get_passes(passInfos);
+        if (ImGui::Button("Reload Pipelines")) { eng->_pipelineManager->hotReloadChanged(); }
+        ImGui::SameLine();
+        ImGui::Text("%zu passes", passInfos.size());
+
+        if (ImGui::BeginTable("passes", 8, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
+        {
+            ImGui::TableSetupColumn("Enable", ImGuiTableColumnFlags_WidthFixed, 70);
+            ImGui::TableSetupColumn("Name");
+            ImGui::TableSetupColumn("Type", ImGuiTableColumnFlags_WidthFixed, 80);
+            ImGui::TableSetupColumn("GPU ms", ImGuiTableColumnFlags_WidthFixed, 70);
+            ImGui::TableSetupColumn("CPU rec ms", ImGuiTableColumnFlags_WidthFixed, 90);
+            ImGui::TableSetupColumn("Imgs", ImGuiTableColumnFlags_WidthFixed, 55);
+            ImGui::TableSetupColumn("Bufs", ImGuiTableColumnFlags_WidthFixed, 55);
+            ImGui::TableSetupColumn("Attachments", ImGuiTableColumnFlags_WidthFixed, 100);
+            ImGui::TableHeadersRow();
+
+            auto typeName = [](RGPassType t){
+                switch (t) {
+                    case RGPassType::Graphics: return "Graphics";
+                    case RGPassType::Compute:  return "Compute";
+                    case RGPassType::Transfer: return "Transfer";
+                    default: return "?";
+                }
+            };
+
+            for (size_t i = 0; i < passInfos.size(); ++i)
+            {
+                auto &pi = passInfos[i];
+                ImGui::TableNextRow();
+                ImGui::TableSetColumnIndex(0);
+                bool enabled = true;
+                if (auto it = eng->_rgPassToggles.find(pi.name); it != eng->_rgPassToggles.end()) enabled = it->second;
+                std::string chkId = std::string("##en") + std::to_string(i);
+                if (ImGui::Checkbox(chkId.c_str(), &enabled))
+                {
+                    eng->_rgPassToggles[pi.name] = enabled;
+                }
+                ImGui::TableSetColumnIndex(1);
+                ImGui::TextUnformatted(pi.name.c_str());
+                ImGui::TableSetColumnIndex(2);
+                ImGui::TextUnformatted(typeName(pi.type));
+                ImGui::TableSetColumnIndex(3);
+                if (pi.gpuMillis >= 0.0f) ImGui::Text("%.2f", pi.gpuMillis); else ImGui::TextUnformatted("-");
+                ImGui::TableSetColumnIndex(4);
+                if (pi.cpuMillis >= 0.0f) ImGui::Text("%.2f", pi.cpuMillis); else ImGui::TextUnformatted("-");
+                ImGui::TableSetColumnIndex(5);
+                ImGui::Text("%u/%u", pi.imageReads, pi.imageWrites);
+                ImGui::TableSetColumnIndex(6);
+                ImGui::Text("%u/%u", pi.bufferReads, pi.bufferWrites);
+                ImGui::TableSetColumnIndex(7);
+                ImGui::Text("%u%s", pi.colorAttachmentCount, pi.hasDepth ? "+D" : "");
+            }
+            ImGui::EndTable();
+        }
+
+        if (ImGui::CollapsingHeader("Images", ImGuiTreeNodeFlags_DefaultOpen))
+        {
+            std::vector<RenderGraph::RGDebugImageInfo> imgs;
+            graph.debug_get_images(imgs);
+            if (ImGui::BeginTable("images", 7, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
+            {
+                ImGui::TableSetupColumn("Id", ImGuiTableColumnFlags_WidthFixed, 40);
+                ImGui::TableSetupColumn("Name");
+                ImGui::TableSetupColumn("Fmt", ImGuiTableColumnFlags_WidthFixed, 120);
+                ImGui::TableSetupColumn("Extent", ImGuiTableColumnFlags_WidthFixed, 120);
+                ImGui::TableSetupColumn("Imported", ImGuiTableColumnFlags_WidthFixed, 70);
+                ImGui::TableSetupColumn("Usage", ImGuiTableColumnFlags_WidthFixed, 80);
+                ImGui::TableSetupColumn("Life", ImGuiTableColumnFlags_WidthFixed, 80);
+                ImGui::TableHeadersRow();
+                for (const auto &im : imgs)
+                {
+                    ImGui::TableNextRow();
+                    ImGui::TableSetColumnIndex(0); ImGui::Text("%u", im.id);
+                    ImGui::TableSetColumnIndex(1); ImGui::TextUnformatted(im.name.c_str());
+                    ImGui::TableSetColumnIndex(2); ImGui::TextUnformatted(string_VkFormat(im.format));
+                    ImGui::TableSetColumnIndex(3); ImGui::Text("%ux%u", im.extent.width, im.extent.height);
+                    ImGui::TableSetColumnIndex(4); ImGui::TextUnformatted(im.imported ? "yes" : "no");
+                    ImGui::TableSetColumnIndex(5); ImGui::Text("0x%x", (unsigned)im.creationUsage);
+                    ImGui::TableSetColumnIndex(6); ImGui::Text("%d..%d", im.firstUse, im.lastUse);
+                }
+                ImGui::EndTable();
+            }
+        }
+
+        if (ImGui::CollapsingHeader("Buffers"))
+        {
+            std::vector<RenderGraph::RGDebugBufferInfo> bufs;
+            graph.debug_get_buffers(bufs);
+            if (ImGui::BeginTable("buffers", 6, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
+            {
+                ImGui::TableSetupColumn("Id", ImGuiTableColumnFlags_WidthFixed, 40);
+                ImGui::TableSetupColumn("Name");
+                ImGui::TableSetupColumn("Size", ImGuiTableColumnFlags_WidthFixed, 100);
+                ImGui::TableSetupColumn("Imported", ImGuiTableColumnFlags_WidthFixed, 70);
+                ImGui::TableSetupColumn("Usage", ImGuiTableColumnFlags_WidthFixed, 100);
+                ImGui::TableSetupColumn("Life", ImGuiTableColumnFlags_WidthFixed, 80);
+                ImGui::TableHeadersRow();
+                for (const auto &bf : bufs)
+                {
+                    ImGui::TableNextRow();
+                    ImGui::TableSetColumnIndex(0); ImGui::Text("%u", bf.id);
+                    ImGui::TableSetColumnIndex(1); ImGui::TextUnformatted(bf.name.c_str());
+                    ImGui::TableSetColumnIndex(2); ImGui::Text("%zu", (size_t)bf.size);
+                    ImGui::TableSetColumnIndex(3); ImGui::TextUnformatted(bf.imported ? "yes" : "no");
+                    ImGui::TableSetColumnIndex(4); ImGui::Text("0x%x", (unsigned)bf.usage);
+                    ImGui::TableSetColumnIndex(5); ImGui::Text("%d..%d", bf.firstUse, bf.lastUse);
+                }
+                ImGui::EndTable();
+            }
+        }
+    }
+
+    // Pipeline manager (graphics)
+    static void ui_pipelines(VulkanEngine *eng)
+    {
+        if (!eng || !eng->_pipelineManager) { ImGui::TextUnformatted("PipelineManager not available"); return; }
+        std::vector<PipelineManager::GraphicsPipelineDebugInfo> pipes;
+        eng->_pipelineManager->debug_get_graphics(pipes);
+        if (ImGui::Button("Reload Changed")) { eng->_pipelineManager->hotReloadChanged(); }
+        ImGui::SameLine(); ImGui::Text("%zu graphics pipelines", pipes.size());
+        if (ImGui::BeginTable("gfxpipes", 5, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
+        {
+            ImGui::TableSetupColumn("Name");
+            ImGui::TableSetupColumn("VS");
+            ImGui::TableSetupColumn("FS");
+            ImGui::TableSetupColumn("Valid", ImGuiTableColumnFlags_WidthFixed, 60);
+            ImGui::TableHeadersRow();
+            for (const auto &p : pipes)
+            {
+                ImGui::TableNextRow();
+                ImGui::TableSetColumnIndex(0); ImGui::TextUnformatted(p.name.c_str());
+                ImGui::TableSetColumnIndex(1); ImGui::TextUnformatted(p.vertexShaderPath.c_str());
+                ImGui::TableSetColumnIndex(2); ImGui::TextUnformatted(p.fragmentShaderPath.c_str());
+                ImGui::TableSetColumnIndex(3); ImGui::TextUnformatted(p.valid ? "yes" : "no");
+            }
+            ImGui::EndTable();
+        }
+    }
+
+    // Post-processing
+    static void ui_postfx(VulkanEngine *eng)
+    {
+        if (!eng) return;
+        if (auto *tm = eng->_renderPassManager ? eng->_renderPassManager->getPass<TonemapPass>() : nullptr)
+        {
+            float exp = tm->exposure();
+            int mode = tm->mode();
+            if (ImGui::SliderFloat("Exposure", &exp, 0.05f, 8.0f)) { tm->setExposure(exp); }
+            ImGui::TextUnformatted("Operator");
+            ImGui::SameLine();
+            if (ImGui::RadioButton("Reinhard", mode == 0)) { mode = 0; tm->setMode(mode); }
+            ImGui::SameLine();
+            if (ImGui::RadioButton("ACES", mode == 1)) { mode = 1; tm->setMode(mode); }
+        }
+        else
+        {
+            ImGui::TextUnformatted("Tonemap pass not available");
+        }
+    }
+
+    // Scene debug bits
+    static void ui_scene(VulkanEngine *eng)
+    {
+        if (!eng) return;
+        const DrawContext &dc = eng->_context->getMainDrawContext();
+        ImGui::Text("Opaque draws: %zu", dc.OpaqueSurfaces.size());
+        ImGui::Text("Transp draws: %zu", dc.TransparentSurfaces.size());
+    }
+} // namespace
+
 VulkanEngine *loadedEngine = nullptr;
 
 static void print_vma_stats(DeviceManager* dev, const char* tag)
@@ -190,7 +452,7 @@ void VulkanEngine::init()
     auto imguiPass = std::make_unique<ImGuiPass>();
     _renderPassManager->setImGuiPass(std::move(imguiPass));
 
-    const std::string structurePath = _assetManager->modelPath("seoul_high.glb");
+    const std::string structurePath = _assetManager->modelPath("mirage.glb");
     const auto structureFile = _assetManager->loadGLTF(structurePath);
 
     assert(structureFile.has_value());
@@ -219,6 +481,11 @@ void VulkanEngine::init_default_data()
     _blackImage = _resourceManager->create_image((void *) &black, VkExtent3D{1, 1, 1}, VK_FORMAT_R8G8B8A8_UNORM,
                                                  VK_IMAGE_USAGE_SAMPLED_BIT);
 
+    // Flat normal (0.5, 0.5, 1.0) for missing normal maps
+    uint32_t flatN = glm::packUnorm4x8(glm::vec4(0.5f, 0.5f, 1.0f, 1.0f));
+    _flatNormalImage = _resourceManager->create_image((void *) &flatN, VkExtent3D{1, 1, 1}, VK_FORMAT_R8G8B8A8_UNORM,
+                                                      VK_IMAGE_USAGE_SAMPLED_BIT);
+
     //checkerboard image
     uint32_t magenta = glm::packUnorm4x8(glm::vec4(1, 0, 1, 1));
     std::array<uint32_t, 16 * 16> pixels{}; //for 16x16 checkerboard texture
@@ -265,6 +532,7 @@ void VulkanEngine::init_default_data()
         _resourceManager->destroy_image(_greyImage);
         _resourceManager->destroy_image(_blackImage);
         _resourceManager->destroy_image(_errorCheckerboardImage);
+        _resourceManager->destroy_image(_flatNormalImage);
     });
     //< default_img
 }
@@ -581,272 +849,51 @@ void VulkanEngine::run()
 
         ImGui::NewFrame();
 
-        if (ImGui::Begin("background"))
+        // Consolidated debug window with tabs
+        if (ImGui::Begin("Debug"))
         {
-            auto background_pass = _renderPassManager->getPass<BackgroundPass>();
+            const ImGuiTabBarFlags tf = ImGuiTabBarFlags_Reorderable | ImGuiTabBarFlags_AutoSelectNewTabs;
-            ComputeEffect &selected = background_pass->_backgroundEffects[background_pass->_currentEffect];
+            if (ImGui::BeginTabBar("DebugTabs", tf))
-
-            ImGui::Text("Selected effect: %s", selected.name);
-
-            ImGui::SliderInt("Effect Index", &background_pass->_currentEffect, 0,
-                             background_pass->_backgroundEffects.size() - 1);
-
-            ImGui::InputFloat4("data1", reinterpret_cast<float *>(&selected.data.data1));
-            ImGui::InputFloat4("data2", reinterpret_cast<float *>(&selected.data.data2));
-            ImGui::InputFloat4("data3", reinterpret_cast<float *>(&selected.data.data3));
-            ImGui::InputFloat4("data4", reinterpret_cast<float *>(&selected.data.data4));
-
-            ImGui::SliderFloat("Render Scale", &renderScale, 0.3f, 1.f);
-
-            ImGui::End();
-        }
-
-        if (ImGui::Begin("Stats"))
-        {
-            ImGui::Text("frametime %f ms", stats.frametime);
-            ImGui::Text("draw time %f ms", stats.mesh_draw_time);
-            ImGui::Text("update time %f ms", _sceneManager->stats.scene_update_time);
-            ImGui::Text("triangles %i", stats.triangle_count);
-            ImGui::Text("draws %i", stats.drawcall_count);
-            ImGui::End();
-        }
-
-        // Shadows / Ray Query settings
-        if (ImGui::Begin("Shadows"))
-        {
-            const bool rq = _deviceManager->supportsRayQuery();
-            const bool as = _deviceManager->supportsAccelerationStructure();
-            ImGui::Text("RayQuery: %s", rq ? "supported" : "not available");
-            ImGui::Text("AccelStruct: %s", as ? "supported" : "not available");
-            ImGui::Separator();
-
-            auto &ss = _context->shadowSettings;
-            // Mode selection
-            int mode = static_cast<int>(ss.mode);
-            ImGui::TextUnformatted("Shadow Mode");
-            ImGui::RadioButton("Clipmap only", &mode, 0); ImGui::SameLine();
-            ImGui::RadioButton("Clipmap + RT", &mode, 1); ImGui::SameLine();
-            ImGui::RadioButton("RT only", &mode, 2);
-            // If device lacks RT support, force mode 0
-            if (!(rq && as) && mode != 0) mode = 0;
-            ss.mode = static_cast<uint32_t>(mode);
-            ss.hybridRayQueryEnabled = (ss.mode != 0);
-
-            // Hybrid controls (mode 1)
-            ImGui::BeginDisabled(ss.mode != 1u);
-            ImGui::TextUnformatted("Cascades using ray assist:");
-            for (int i = 0; i < 4; ++i)
             {
-                bool on = (ss.hybridRayCascadesMask >> i) & 1u;
+                if (ImGui::BeginTabItem("Overview"))
-                std::string label = std::string("C") + std::to_string(i);
-                if (ImGui::Checkbox(label.c_str(), &on))
                 {
-                    if (on) ss.hybridRayCascadesMask |= (1u << i);
+                    ui_overview(this);
-                    else    ss.hybridRayCascadesMask &= ~(1u << i);
+                    ImGui::EndTabItem();
                 }
-                if (i != 3) ImGui::SameLine();
+                if (ImGui::BeginTabItem("Background"))
-            }
-            ImGui::SliderFloat("N·L threshold", &ss.hybridRayNoLThreshold, 0.0f, 1.0f, "%.2f");
-            ImGui::EndDisabled();
-
-            ImGui::Separator();
-            ImGui::TextWrapped("Clipmap only: raster PCF+RPDB. Clipmap+RT: PCF assisted by ray query at low N·L. RT only: skip shadow maps and use ray tests only.");
-
-            ImGui::End();
-        }
-
-        // Render Graph debug window
-        if (ImGui::Begin("Render Graph"))
-        {
-            if (_renderGraph)
-            {
-                auto &graph = *_renderGraph;
-                std::vector<RenderGraph::RGDebugPassInfo> passInfos;
-                graph.debug_get_passes(passInfos);
-                if (ImGui::Button("Reload Pipelines")) { _pipelineManager->hotReloadChanged(); }
-                ImGui::SameLine();
-                ImGui::Text("%zu passes", passInfos.size());
-
-                if (ImGui::BeginTable("passes", 8, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
                 {
-                    ImGui::TableSetupColumn("Enable", ImGuiTableColumnFlags_WidthFixed, 70);
+                    ui_background(this);
-                    ImGui::TableSetupColumn("Name");
+                    ImGui::EndTabItem();
-                    ImGui::TableSetupColumn("Type", ImGuiTableColumnFlags_WidthFixed, 80);
-                    ImGui::TableSetupColumn("GPU ms", ImGuiTableColumnFlags_WidthFixed, 70);
-                    ImGui::TableSetupColumn("CPU rec ms", ImGuiTableColumnFlags_WidthFixed, 90);
-                    ImGui::TableSetupColumn("Imgs", ImGuiTableColumnFlags_WidthFixed, 55);
-                    ImGui::TableSetupColumn("Bufs", ImGuiTableColumnFlags_WidthFixed, 55);
-                    ImGui::TableSetupColumn("Attachments", ImGuiTableColumnFlags_WidthFixed, 100);
-                    ImGui::TableHeadersRow();
-
-                    auto typeName = [](RGPassType t){
-                        switch (t) {
-                            case RGPassType::Graphics: return "Graphics";
-                            case RGPassType::Compute:  return "Compute";
-                            case RGPassType::Transfer: return "Transfer";
-                            default: return "?";
-                        }
-                    };
-
-                    for (size_t i = 0; i < passInfos.size(); ++i)
-                    {
-                        auto &pi = passInfos[i];
-                        ImGui::TableNextRow();
-                        ImGui::TableSetColumnIndex(0);
-                        bool enabled = true;
-                        if (auto it = _rgPassToggles.find(pi.name); it != _rgPassToggles.end()) enabled = it->second;
-                        std::string chkId = std::string("##en") + std::to_string(i);
-                        if (ImGui::Checkbox(chkId.c_str(), &enabled))
-                        {
-                            _rgPassToggles[pi.name] = enabled;
-                        }
-                        ImGui::TableSetColumnIndex(1);
-                        ImGui::TextUnformatted(pi.name.c_str());
-                        ImGui::TableSetColumnIndex(2);
-                        ImGui::TextUnformatted(typeName(pi.type));
-                        ImGui::TableSetColumnIndex(3);
-                        if (pi.gpuMillis >= 0.0f) ImGui::Text("%.2f", pi.gpuMillis); else ImGui::TextUnformatted("-");
-                        ImGui::TableSetColumnIndex(4);
-                        if (pi.cpuMillis >= 0.0f) ImGui::Text("%.2f", pi.cpuMillis); else ImGui::TextUnformatted("-");
-                        ImGui::TableSetColumnIndex(5);
-                        ImGui::Text("%u/%u", pi.imageReads, pi.imageWrites);
-                        ImGui::TableSetColumnIndex(6);
-                        ImGui::Text("%u/%u", pi.bufferReads, pi.bufferWrites);
-                        ImGui::TableSetColumnIndex(7);
-                        ImGui::Text("%u%s", pi.colorAttachmentCount, pi.hasDepth ? "+D" : "");
-                    }
-                    ImGui::EndTable();
                 }
-
+                if (ImGui::BeginTabItem("Shadows"))
-                if (ImGui::CollapsingHeader("Images", ImGuiTreeNodeFlags_DefaultOpen))
                 {
-                    std::vector<RenderGraph::RGDebugImageInfo> imgs;
+                    ui_shadows(this);
-                    graph.debug_get_images(imgs);
+                    ImGui::EndTabItem();
-                    if (ImGui::BeginTable("images", 7, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
-                    {
-                        ImGui::TableSetupColumn("Id", ImGuiTableColumnFlags_WidthFixed, 40);
-                        ImGui::TableSetupColumn("Name");
-                        ImGui::TableSetupColumn("Fmt", ImGuiTableColumnFlags_WidthFixed, 120);
-                        ImGui::TableSetupColumn("Extent", ImGuiTableColumnFlags_WidthFixed, 120);
-                        ImGui::TableSetupColumn("Imported", ImGuiTableColumnFlags_WidthFixed, 70);
-                        ImGui::TableSetupColumn("Usage", ImGuiTableColumnFlags_WidthFixed, 80);
-                        ImGui::TableSetupColumn("Life", ImGuiTableColumnFlags_WidthFixed, 80);
-                        ImGui::TableHeadersRow();
-                        for (const auto &im : imgs)
-                        {
-                            ImGui::TableNextRow();
-                            ImGui::TableSetColumnIndex(0); ImGui::Text("%u", im.id);
-                            ImGui::TableSetColumnIndex(1); ImGui::TextUnformatted(im.name.c_str());
-                            ImGui::TableSetColumnIndex(2); ImGui::TextUnformatted(string_VkFormat(im.format));
-                            ImGui::TableSetColumnIndex(3); ImGui::Text("%ux%u", im.extent.width, im.extent.height);
-                            ImGui::TableSetColumnIndex(4); ImGui::TextUnformatted(im.imported ? "yes" : "no");
-                            ImGui::TableSetColumnIndex(5); ImGui::Text("0x%x", (unsigned)im.creationUsage);
-                            ImGui::TableSetColumnIndex(6); ImGui::Text("%d..%d", im.firstUse, im.lastUse);
-                        }
-                        ImGui::EndTable();
-                    }
                 }
-
+                if (ImGui::BeginTabItem("Render Graph"))
-                if (ImGui::CollapsingHeader("Buffers"))
                 {
-                    std::vector<RenderGraph::RGDebugBufferInfo> bufs;
+                    ui_render_graph(this);
-                    graph.debug_get_buffers(bufs);
+                    ImGui::EndTabItem();
-                    if (ImGui::BeginTable("buffers", 6, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
-                    {
-                        ImGui::TableSetupColumn("Id", ImGuiTableColumnFlags_WidthFixed, 40);
-                        ImGui::TableSetupColumn("Name");
-                        ImGui::TableSetupColumn("Size", ImGuiTableColumnFlags_WidthFixed, 100);
-                        ImGui::TableSetupColumn("Imported", ImGuiTableColumnFlags_WidthFixed, 70);
-                        ImGui::TableSetupColumn("Usage", ImGuiTableColumnFlags_WidthFixed, 100);
-                        ImGui::TableSetupColumn("Life", ImGuiTableColumnFlags_WidthFixed, 80);
-                        ImGui::TableHeadersRow();
-                        for (const auto &bf : bufs)
-                        {
-                            ImGui::TableNextRow();
-                            ImGui::TableSetColumnIndex(0); ImGui::Text("%u", bf.id);
-                            ImGui::TableSetColumnIndex(1); ImGui::TextUnformatted(bf.name.c_str());
-                            ImGui::TableSetColumnIndex(2); ImGui::Text("%zu", (size_t)bf.size);
-                            ImGui::TableSetColumnIndex(3); ImGui::TextUnformatted(bf.imported ? "yes" : "no");
-                            ImGui::TableSetColumnIndex(4); ImGui::Text("0x%x", (unsigned)bf.usage);
-                            ImGui::TableSetColumnIndex(5); ImGui::Text("%d..%d", bf.firstUse, bf.lastUse);
-                        }
-                        ImGui::EndTable();
-                    }
                 }
-            }
+                if (ImGui::BeginTabItem("Pipelines"))
-            ImGui::End();
-        }
-
-        // Pipelines debug window (graphics)
-        if (ImGui::Begin("Pipelines"))
-        {
-            if (_pipelineManager)
-            {
-                std::vector<PipelineManager::GraphicsPipelineDebugInfo> pipes;
-                _pipelineManager->debug_get_graphics(pipes);
-                if (ImGui::Button("Reload Changed")) { _pipelineManager->hotReloadChanged(); }
-                ImGui::SameLine(); ImGui::Text("%zu graphics pipelines", pipes.size());
-                if (ImGui::BeginTable("gfxpipes", 5, ImGuiTableFlags_RowBg | ImGuiTableFlags_SizingStretchProp))
                 {
-                    ImGui::TableSetupColumn("Name");
+                    ui_pipelines(this);
-                    ImGui::TableSetupColumn("VS");
+                    ImGui::EndTabItem();
-                    ImGui::TableSetupColumn("FS");
-                    ImGui::TableSetupColumn("Valid", ImGuiTableColumnFlags_WidthFixed, 60);
-                    ImGui::TableHeadersRow();
-                    for (const auto &p : pipes)
-                    {
-                        ImGui::TableNextRow();
-                        ImGui::TableSetColumnIndex(0); ImGui::TextUnformatted(p.name.c_str());
-                        ImGui::TableSetColumnIndex(1); ImGui::TextUnformatted(p.vertexShaderPath.c_str());
-                        ImGui::TableSetColumnIndex(2); ImGui::TextUnformatted(p.fragmentShaderPath.c_str());
-                        ImGui::TableSetColumnIndex(3); ImGui::TextUnformatted(p.valid ? "yes" : "no");
-                    }
-                    ImGui::EndTable();
                 }
+                if (ImGui::BeginTabItem("PostFX"))
+                {
+                    ui_postfx(this);
+                    ImGui::EndTabItem();
+                }
+                if (ImGui::BeginTabItem("Scene"))
+                {
+                    ui_scene(this);
+                    ImGui::EndTabItem();
+                }
+                ImGui::EndTabBar();
             }
             ImGui::End();
         }
-
-    // Draw targets window
-        if (ImGui::Begin("Targets"))
-        {
-            ImGui::Text("Draw extent: %ux%u", _drawExtent.width, _drawExtent.height);
-            auto scExt = _swapchainManager->swapchainExtent();
-            ImGui::Text("Swapchain:   %ux%u", scExt.width, scExt.height);
-            ImGui::Text("Draw fmt:    %s", string_VkFormat(_swapchainManager->drawImage().imageFormat));
-            ImGui::Text("Swap fmt:    %s", string_VkFormat(_swapchainManager->swapchainImageFormat()));
-            ImGui::End();
-        }
-
-        // PostFX window
-        if (ImGui::Begin("PostFX"))
-        {
-            if (auto *tm = _renderPassManager->getPass<TonemapPass>())
-            {
-                float exp = tm->exposure();
-                int mode = tm->mode();
-                if (ImGui::SliderFloat("Exposure", &exp, 0.05f, 8.0f)) { tm->setExposure(exp); }
-                ImGui::TextUnformatted("Operator");
-                ImGui::SameLine();
-                if (ImGui::RadioButton("Reinhard", mode == 0)) { mode = 0; tm->setMode(mode); }
-                ImGui::SameLine();
-                if (ImGui::RadioButton("ACES", mode == 1)) { mode = 1; tm->setMode(mode); }
-            }
-            else
-            {
-                ImGui::TextUnformatted("Tonemap pass not available");
-            }
-            ImGui::End();
-        }
-
-        // Scene window
-        if (ImGui::Begin("Scene"))
-        {
-            const DrawContext &dc = _context->getMainDrawContext();
-            ImGui::Text("Opaque draws: %zu", dc.OpaqueSurfaces.size());
-            ImGui::Text("Transp draws: %zu", dc.TransparentSurfaces.size());
-            ImGui::End();
-        }
         ImGui::Render();
         draw();
 

src/core/vk_engine.h

@@ -97,6 +97,7 @@ public:
 	AllocatedImage _blackImage;
 	AllocatedImage _greyImage;
 	AllocatedImage _errorCheckerboardImage;
+    AllocatedImage _flatNormalImage; // 1x1 (0.5,0.5,1.0)
 
     MaterialInstance defaultData;
 

src/core/vk_types.h

@@ -107,6 +107,8 @@ struct Vertex {
     glm::vec3 normal;
     float uv_y;
     glm::vec4 color;
+    // Tangent.xyz = tangent direction; Tangent.w = handedness sign for B = sign * cross(N, T)
+    glm::vec4 tangent;
 };
 
 // holds the resources needed for a mesh

src/render/primitives.h

@@ -24,10 +24,10 @@ inline void buildCube(std::vector<Vertex>& vertices, std::vector<uint32_t>& indi
 
     for (auto& f : faces) {
         uint32_t start = (uint32_t)vertices.size();
-        Vertex v0{f.v0, 0, f.normal, 0, glm::vec4(1.0f)};
+        Vertex v0{f.v0, 0, f.normal, 0, glm::vec4(1.0f), glm::vec4(1,0,0,1)};
-        Vertex v1{f.v1, 1, f.normal, 0, glm::vec4(1.0f)};
+        Vertex v1{f.v1, 1, f.normal, 0, glm::vec4(1.0f), glm::vec4(1,0,0,1)};
-        Vertex v2{f.v2, 0, f.normal, 1, glm::vec4(1.0f)};
+        Vertex v2{f.v2, 0, f.normal, 1, glm::vec4(1.0f), glm::vec4(1,0,0,1)};
-        Vertex v3{f.v3, 1, f.normal, 1, glm::vec4(1.0f)};
+        Vertex v3{f.v3, 1, f.normal, 1, glm::vec4(1.0f), glm::vec4(1,0,0,1)};
         vertices.push_back(v0);
         vertices.push_back(v1);
         vertices.push_back(v2);
@@ -61,6 +61,7 @@ inline void buildSphere(std::vector<Vertex>& vertices, std::vector<uint32_t>& in
             vert.uv_x = u;
             vert.uv_y = 1.0f - v;
             vert.color = glm::vec4(1.0f);
+            vert.tangent = glm::vec4(1,0,0,1);
             vertices.push_back(vert);
         }
     }

src/render/vk_materials.cpp

@@ -19,6 +19,7 @@ void GLTFMetallic_Roughness::build_pipelines(VulkanEngine *engine)
     layoutBuilder.add_binding(0, VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER);
     layoutBuilder.add_binding(1, VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER);
     layoutBuilder.add_binding(2, VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER);
+    layoutBuilder.add_binding(3, VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER);
 
     materialLayout = layoutBuilder.build(engine->_deviceManager->device(),
                                          VK_SHADER_STAGE_VERTEX_BIT | VK_SHADER_STAGE_FRAGMENT_BIT,
@@ -120,6 +121,8 @@ MaterialInstance GLTFMetallic_Roughness::write_material(VkDevice device, Materia
                        VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL, VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER);
     writer.write_image(2, resources.metalRoughImage.imageView, resources.metalRoughSampler,
                        VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL, VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER);
+    writer.write_image(3, resources.normalImage.imageView, resources.normalSampler,
+                       VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL, VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER);
 
     writer.update_set(device, matData.materialSet);
 

src/render/vk_materials.h

@@ -27,6 +27,8 @@ struct GLTFMetallic_Roughness
         VkSampler colorSampler;
         AllocatedImage metalRoughImage;
         VkSampler metalRoughSampler;
+        AllocatedImage normalImage;
+        VkSampler normalSampler;
         VkBuffer dataBuffer;
         uint32_t dataBufferOffset;
     };

src/scene/tangent_space.cpp

@@ -0,0 +1,219 @@
+#include "tangent_space.h"
+
+#include <glm/glm.hpp>
+#include <glm/gtc/epsilon.hpp>
+#include <algorithm>
+
+#include "glm/gtx/norm.hpp"
+
+namespace
+{
+    struct Range
+    {
+        size_t indexStart;
+        size_t indexCount;
+        size_t vertexStart;
+        size_t vertexCount;
+    };
+
+    static inline glm::vec3 orthonormal_tangent(const glm::vec3 &n)
+    {
+        // Build tangent orthogonal to n from an arbitrary axis
+        glm::vec3 a = (std::abs(n.z) < 0.999f) ? glm::vec3(0, 0, 1) : glm::vec3(0, 1, 0);
+        glm::vec3 t = glm::normalize(glm::cross(a, n));
+        return t;
+    }
+
+    static void generate_fallback(std::vector<Vertex> &vtx, const Range &r)
+    {
+        for (size_t i = 0; i < r.vertexCount; ++i)
+        {
+            Vertex &v = vtx[r.vertexStart + i];
+            glm::vec3 T = orthonormal_tangent(glm::normalize(v.normal));
+            v.tangent = glm::vec4(T, 1.0f);
+        }
+    }
+} // namespace
+
+namespace geom
+{
+#ifdef MIKKTS_ENABLE
+#include <mikktspace.h>
+
+    struct MikkAdapter
+    {
+        std::vector<Vertex> *verts;
+        const std::vector<uint32_t> *inds;
+        Range range;
+    };
+
+    static int mikk_get_num_faces(const SMikkTSpaceContext *ctx)
+    {
+        const MikkAdapter *ad = reinterpret_cast<const MikkAdapter *>(ctx->m_pUserData);
+        return static_cast<int>(ad->range.indexCount / 3);
+    }
+
+    static int mikk_get_num_verts_of_face(const SMikkTSpaceContext *, const int /*face*/) { return 3; }
+
+    static void mikk_get_position(const SMikkTSpaceContext *ctx, float outpos[], const int face, const int vert)
+    {
+        const MikkAdapter *ad = reinterpret_cast<const MikkAdapter *>(ctx->m_pUserData);
+        uint32_t idx = ad->inds->at(ad->range.indexStart + face * 3 + vert);
+        const Vertex &v = ad->verts->at(idx);
+        outpos[0] = v.position.x;
+        outpos[1] = v.position.y;
+        outpos[2] = v.position.z;
+    }
+
+    static void mikk_get_normal(const SMikkTSpaceContext *ctx, float outnormal[], const int face, const int vert)
+    {
+        const MikkAdapter *ad = reinterpret_cast<const MikkAdapter *>(ctx->m_pUserData);
+        uint32_t idx = ad->inds->at(ad->range.indexStart + face * 3 + vert);
+        const Vertex &v = ad->verts->at(idx);
+        outnormal[0] = v.normal.x;
+        outnormal[1] = v.normal.y;
+        outnormal[2] = v.normal.z;
+    }
+
+    static void mikk_get_texcoord(const SMikkTSpaceContext *ctx, float outuv[], const int face, const int vert)
+    {
+        const MikkAdapter *ad = reinterpret_cast<const MikkAdapter *>(ctx->m_pUserData);
+        uint32_t idx = ad->inds->at(ad->range.indexStart + face * 3 + vert);
+        const Vertex &v = ad->verts->at(idx);
+        outuv[0] = v.uv_x;
+        outuv[1] = v.uv_y;
+    }
+
+    static void mikk_set_tspace_basic(const SMikkTSpaceContext *ctx, const float tangent[], const float sign,
+                                      const int face, const int vert)
+    {
+        const MikkAdapter *ad = reinterpret_cast<const MikkAdapter *>(ctx->m_pUserData);
+        uint32_t idx = ad->inds->at(ad->range.indexStart + face * 3 + vert);
+        Vertex &v = ad->verts->at(idx);
+        v.tangent = glm::vec4(tangent[0], tangent[1], tangent[2], sign);
+    }
+
+    static bool generate_mikk(std::vector<Vertex> &vertices, const std::vector<uint32_t> &indices, const Range &r)
+    {
+        SMikkTSpaceInterface iface{};
+        iface.m_getNumFaces = mikk_get_num_faces;
+        iface.m_getNumVerticesOfFace = mikk_get_num_verts_of_face;
+        iface.m_getPosition = mikk_get_position;
+        iface.m_getNormal = mikk_get_normal;
+        iface.m_getTexCoord = mikk_get_texcoord;
+        iface.m_setTSpaceBasic = mikk_set_tspace_basic;
+
+        MikkAdapter ad{&vertices, &indices, r};
+        SMikkTSpaceContext ctx{};
+        ctx.m_pInterface = &iface;
+        ctx.m_pUserData = &ad;
+
+        // angle weighting, respect vtx-deriv continuity by default
+        return genTangSpaceDefault(&ctx) != 0;
+    }
+#endif // MIKKTS_ENABLE
+
+    void generate_tangents_range(std::vector<Vertex> &vertices, const std::vector<uint32_t> &indices,
+                                 size_t indexStart, size_t indexCount,
+                                 size_t vertexStart, size_t vertexCount)
+    {
+        Range r{indexStart, indexCount, vertexStart, vertexCount};
+
+        if (indexCount < 3 || vertexCount == 0)
+        {
+            generate_fallback(vertices, r);
+            return;
+        }
+
+#ifdef MIKKTS_ENABLE
+        if (generate_mikk(vertices, indices, r))
+        {
+            return;
+        }
+#endif
+
+        std::vector<glm::vec3> tan1(vertexCount, glm::vec3(0.0f));
+        std::vector<glm::vec3> bit1(vertexCount, glm::vec3(0.0f));
+
+        bool anyValid = false;
+        for (size_t it = 0; it + 2 < indexCount; it += 3)
+        {
+            uint32_t i0 = indices[r.indexStart + it];
+            uint32_t i1 = indices[r.indexStart + it + 1];
+            uint32_t i2 = indices[r.indexStart + it + 2];
+
+            // guard against out of range
+            if (i0 < r.vertexStart || i1 < r.vertexStart || i2 < r.vertexStart) continue;
+            if (i0 >= r.vertexStart + r.vertexCount || i1 >= r.vertexStart + r.vertexCount || i2 >= r.vertexStart + r.
+                vertexCount) continue;
+
+            const Vertex &v0 = vertices[i0];
+            const Vertex &v1 = vertices[i1];
+            const Vertex &v2 = vertices[i2];
+
+            glm::vec3 p0 = v0.position;
+            glm::vec3 p1 = v1.position;
+            glm::vec3 p2 = v2.position;
+
+            glm::vec2 w0{v0.uv_x, v0.uv_y};
+            glm::vec2 w1{v1.uv_x, v1.uv_y};
+            glm::vec2 w2{v2.uv_x, v2.uv_y};
+
+            glm::vec3 e1 = p1 - p0;
+            glm::vec3 e2 = p2 - p0;
+            glm::vec2 d1 = w1 - w0;
+            glm::vec2 d2 = w2 - w0;
+
+            float denom = d1.x * d2.y - d1.y * d2.x;
+            if (std::abs(denom) < 1e-8f)
+            {
+                continue; // degenerate UV mapping; skip this tri
+            }
+            anyValid = true;
+            float rcp = 1.0f / denom;
+            glm::vec3 t = (e1 * d2.y - e2 * d1.y) * rcp;
+            glm::vec3 b = (-e1 * d2.x + e2 * d1.x) * rcp;
+
+            size_t l0 = i0 - r.vertexStart;
+            size_t l1 = i1 - r.vertexStart;
+            size_t l2 = i2 - r.vertexStart;
+            tan1[l0] += t;
+            tan1[l1] += t;
+            tan1[l2] += t;
+            bit1[l0] += b;
+            bit1[l1] += b;
+            bit1[l2] += b;
+        }
+
+        if (!anyValid)
+        {
+            generate_fallback(vertices, r);
+            return;
+        }
+
+        for (size_t i = 0; i < r.vertexCount; ++i)
+        {
+            Vertex &v = vertices[r.vertexStart + i];
+            glm::vec3 N = glm::normalize(v.normal);
+            glm::vec3 T = tan1[i];
+            glm::vec3 B = bit1[i];
+            if (glm::length2(T) < 1e-16f)
+            {
+                T = orthonormal_tangent(N);
+                v.tangent = glm::vec4(T, 1.0f);
+                continue;
+            }
+            // Gram-Schmidt orthonormalize
+            T = glm::normalize(T - N * glm::dot(N, T));
+            // Compute handedness
+            float w = (glm::dot(glm::cross(N, T), B) < 0.0f) ? -1.0f : 1.0f;
+            v.tangent = glm::vec4(T, w);
+        }
+    }
+
+    void generate_tangents(std::vector<Vertex> &vertices, const std::vector<uint32_t> &indices)
+    {
+        if (vertices.empty() || indices.size() < 3) return;
+        generate_tangents_range(vertices, indices, 0, indices.size(), 0, vertices.size());
+    }
+} // namespace geom

src/scene/tangent_space.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <vector>
+#include <cstddef>
+#include <core/vk_types.h>
+
+namespace geom {
+
+// Generate per-vertex tangents with a robust fallback when MikkTSpace is not available.
+// - Fills Vertex.tangent (xyz = tangent, w = handedness sign for B = sign * cross(N, T))
+// - Expects valid normals and UVs; if UVs are degenerate, builds an arbitrary orthonormal basis.
+void generate_tangents(std::vector<Vertex>& vertices, const std::vector<uint32_t>& indices);
+
+// Range variant for submeshes (indices [indexStart, indexStart+indexCount), vertices [vertexStart, vertexStart+vertexCount))
+void generate_tangents_range(std::vector<Vertex>& vertices, const std::vector<uint32_t>& indices,
+                             size_t indexStart, size_t indexCount,
+                             size_t vertexStart, size_t vertexCount);
+
+} // namespace geom
+

src/scene/vk_loader.cpp

@@ -14,6 +14,7 @@
 #include <fastgltf/tools.hpp>
 #include <fastgltf/util.hpp>
 #include <optional>
+#include "tangent_space.h"
 //> loadimg
 std::optional<AllocatedImage> load_image(VulkanEngine *engine, fastgltf::Asset &asset, fastgltf::Image &image, bool srgb)
 {
@@ -312,6 +313,8 @@ std::optional<std::shared_ptr<LoadedGLTF> > loadGltf(VulkanEngine *engine, std::
         file.materials[mat.name.c_str()] = newMat;
 
         GLTFMetallic_Roughness::MaterialConstants constants;
+        // Defaults
+        constants.extra[0].x = 1.0f; // normalScale
         constants.colorFactors.x = mat.pbrData.baseColorFactor[0];
         constants.colorFactors.y = mat.pbrData.baseColorFactor[1];
         constants.colorFactors.z = mat.pbrData.baseColorFactor[2];
@@ -334,6 +337,8 @@ std::optional<std::shared_ptr<LoadedGLTF> > loadGltf(VulkanEngine *engine, std::
         materialResources.colorSampler = engine->_samplerManager->defaultLinear();
         materialResources.metalRoughImage = engine->_whiteImage;
         materialResources.metalRoughSampler = engine->_samplerManager->defaultLinear();
+        materialResources.normalImage = engine->_flatNormalImage;
+        materialResources.normalSampler = engine->_samplerManager->defaultLinear();
 
         // set the uniform buffer for the material data
         materialResources.dataBuffer = file.materialDataBuffer.buffer;
@@ -385,6 +390,39 @@ std::optional<std::shared_ptr<LoadedGLTF> > loadGltf(VulkanEngine *engine, std::
                                                                   : engine->_samplerManager->defaultLinear();
             }
         }
+
+        // Normal map (tangent-space)
+        if (mat.normalTexture.has_value())
+        {
+            const auto &tex = gltf.textures[mat.normalTexture.value().textureIndex];
+            size_t imgIndex = tex.imageIndex.value();
+            bool hasSampler = tex.samplerIndex.has_value();
+            size_t sampler = hasSampler ? tex.samplerIndex.value() : SIZE_MAX;
+
+            if (imgIndex < gltf.images.size())
+            {
+                auto normalImg = load_image(engine, gltf, gltf.images[imgIndex], false);
+                if (normalImg.has_value())
+                {
+                    materialResources.normalImage = *normalImg;
+                    std::string key = std::string("normal_") + mat.name.c_str() + "_" + std::to_string(imgIndex);
+                    file.images[key] = *normalImg;
+                }
+                else
+                {
+                    materialResources.normalImage = images[imgIndex];
+                }
+            }
+            else
+            {
+                materialResources.normalImage = engine->_flatNormalImage;
+            }
+            materialResources.normalSampler = hasSampler ? file.samplers[sampler]
+                                                         : engine->_samplerManager->defaultLinear();
+
+            // Store normal scale into material constants extra[0].x if available
+            sceneMaterialConstants[data_index].extra[0].x = mat.normalTexture->scale;
+        }
         // build material
         newMat->data = engine->metalRoughMaterial.write_material(engine->_deviceManager->device(), passType, materialResources,
                                                                  file.descriptorPool);
@@ -442,12 +480,13 @@ std::optional<std::shared_ptr<LoadedGLTF> > loadGltf(VulkanEngine *engine, std::
 
                 fastgltf::iterateAccessorWithIndex<glm::vec3>(gltf, posAccessor,
                                                               [&](glm::vec3 v, size_t index) {
-                                                                  Vertex newvtx;
+                                                                  Vertex newvtx{};
                                                                   newvtx.position = v;
                                                                   newvtx.normal = {1, 0, 0};
                                                                   newvtx.color = glm::vec4{1.f};
                                                                   newvtx.uv_x = 0;
                                                                   newvtx.uv_y = 0;
+                                                                  newvtx.tangent = glm::vec4(1,0,0,1);
                                                                   vertices[initial_vtx + index] = newvtx;
                                                               });
             }
@@ -483,6 +522,29 @@ std::optional<std::shared_ptr<LoadedGLTF> > loadGltf(VulkanEngine *engine, std::
                                                               });
             }
 
+            // load tangents if present (vec4, w = sign)
+            auto tangents = p.findAttribute("TANGENT");
+            bool hasTangents = tangents != p.attributes.end();
+            if (hasTangents)
+            {
+                fastgltf::iterateAccessorWithIndex<glm::vec4>(gltf, gltf.accessors[(*tangents).second],
+                                                              [&](glm::vec4 v, size_t index) {
+                                                                  vertices[initial_vtx + index].tangent = v;
+                                                              });
+            }
+
+            // Generate tangents if missing and we have UVs
+            if (!hasTangents)
+            {
+                size_t primIndexStart = newSurface.startIndex;
+                size_t primIndexCount = newSurface.count;
+                size_t primVertexStart = initial_vtx;
+                size_t primVertexCount = vertices.size() - initial_vtx;
+                geom::generate_tangents_range(vertices, indices,
+                                              primIndexStart, primIndexCount,
+                                              primVertexStart, primVertexCount);
+            }
+
             if (p.materialIndex.has_value())
             {
                 newSurface.material = materials[p.materialIndex.value()];

third_party/CMakeLists.txt

@@ -50,3 +50,7 @@ target_sources(imgui PRIVATE
 target_link_libraries(imgui PUBLIC Vulkan::Vulkan SDL2::SDL2)
 
 target_include_directories(stb_image INTERFACE stb_image)
+
+# MikkTSpace (optional)
+add_library(mikktspace STATIC MikkTSpace/mikktspace.c)
+target_include_directories(mikktspace PUBLIC MikkTSpace)

third_party/MikkTSpace/README.md

@@ -0,0 +1,4 @@
+# MikkTSpace
+A common standard for tangent space used in baking tools to produce normal maps.
+
+More information can be found at http://www.mikktspace.com/.

third_party/MikkTSpace/mikktspace.h

@@ -0,0 +1,145 @@
+/** \file mikktspace/mikktspace.h
+ *  \ingroup mikktspace
+ */
+/**
+ *  Copyright (C) 2011 by Morten S. Mikkelsen
+ *
+ *  This software is provided 'as-is', without any express or implied
+ *  warranty.  In no event will the authors be held liable for any damages
+ *  arising from the use of this software.
+ *
+ *  Permission is granted to anyone to use this software for any purpose,
+ *  including commercial applications, and to alter it and redistribute it
+ *  freely, subject to the following restrictions:
+ *
+ *  1. The origin of this software must not be misrepresented; you must not
+ *     claim that you wrote the original software. If you use this software
+ *     in a product, an acknowledgment in the product documentation would be
+ *     appreciated but is not required.
+ *  2. Altered source versions must be plainly marked as such, and must not be
+ *     misrepresented as being the original software.
+ *  3. This notice may not be removed or altered from any source distribution.
+ */
+
+#ifndef __MIKKTSPACE_H__
+#define __MIKKTSPACE_H__
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Author: Morten S. Mikkelsen
+ * Version: 1.0
+ *
+ * The files mikktspace.h and mikktspace.c are designed to be
+ * stand-alone files and it is important that they are kept this way.
+ * Not having dependencies on structures/classes/libraries specific
+ * to the program, in which they are used, allows them to be copied
+ * and used as is into any tool, program or plugin.
+ * The code is designed to consistently generate the same
+ * tangent spaces, for a given mesh, in any tool in which it is used.
+ * This is done by performing an internal welding step and subsequently an order-independent evaluation
+ * of tangent space for meshes consisting of triangles and quads.
+ * This means faces can be received in any order and the same is true for
+ * the order of vertices of each face. The generated result will not be affected
+ * by such reordering. Additionally, whether degenerate (vertices or texture coordinates)
+ * primitives are present or not will not affect the generated results either.
+ * Once tangent space calculation is done the vertices of degenerate primitives will simply
+ * inherit tangent space from neighboring non degenerate primitives.
+ * The analysis behind this implementation can be found in my master's thesis
+ * which is available for download --> http://image.diku.dk/projects/media/morten.mikkelsen.08.pdf
+ * Note that though the tangent spaces at the vertices are generated in an order-independent way,
+ * by this implementation, the interpolated tangent space is still affected by which diagonal is
+ * chosen to split each quad. A sensible solution is to have your tools pipeline always
+ * split quads by the shortest diagonal. This choice is order-independent and works with mirroring.
+ * If these have the same length then compare the diagonals defined by the texture coordinates.
+ * XNormal which is a tool for baking normal maps allows you to write your own tangent space plugin
+ * and also quad triangulator plugin.
+ */
+
+
+typedef int tbool;
+typedef struct SMikkTSpaceContext SMikkTSpaceContext;
+
+typedef struct {
+	// Returns the number of faces (triangles/quads) on the mesh to be processed.
+	int (*m_getNumFaces)(const SMikkTSpaceContext * pContext);
+
+	// Returns the number of vertices on face number iFace
+	// iFace is a number in the range {0, 1, ..., getNumFaces()-1}
+	int (*m_getNumVerticesOfFace)(const SMikkTSpaceContext * pContext, const int iFace);
+
+	// returns the position/normal/texcoord of the referenced face of vertex number iVert.
+	// iVert is in the range {0,1,2} for triangles and {0,1,2,3} for quads.
+	void (*m_getPosition)(const SMikkTSpaceContext * pContext, float fvPosOut[], const int iFace, const int iVert);
+	void (*m_getNormal)(const SMikkTSpaceContext * pContext, float fvNormOut[], const int iFace, const int iVert);
+	void (*m_getTexCoord)(const SMikkTSpaceContext * pContext, float fvTexcOut[], const int iFace, const int iVert);
+
+	// either (or both) of the two setTSpace callbacks can be set.
+	// The call-back m_setTSpaceBasic() is sufficient for basic normal mapping.
+
+	// This function is used to return the tangent and fSign to the application.
+	// fvTangent is a unit length vector.
+	// For normal maps it is sufficient to use the following simplified version of the bitangent which is generated at pixel/vertex level.
+	// bitangent = fSign * cross(vN, tangent);
+	// Note that the results are returned unindexed. It is possible to generate a new index list
+	// But averaging/overwriting tangent spaces by using an already existing index list WILL produce INCRORRECT results.
+	// DO NOT! use an already existing index list.
+	void (*m_setTSpaceBasic)(const SMikkTSpaceContext * pContext, const float fvTangent[], const float fSign, const int iFace, const int iVert);
+
+	// This function is used to return tangent space results to the application.
+	// fvTangent and fvBiTangent are unit length vectors and fMagS and fMagT are their
+	// true magnitudes which can be used for relief mapping effects.
+	// fvBiTangent is the "real" bitangent and thus may not be perpendicular to fvTangent.
+	// However, both are perpendicular to the vertex normal.
+	// For normal maps it is sufficient to use the following simplified version of the bitangent which is generated at pixel/vertex level.
+	// fSign = bIsOrientationPreserving ? 1.0f : (-1.0f);
+	// bitangent = fSign * cross(vN, tangent);
+	// Note that the results are returned unindexed. It is possible to generate a new index list
+	// But averaging/overwriting tangent spaces by using an already existing index list WILL produce INCRORRECT results.
+	// DO NOT! use an already existing index list.
+	void (*m_setTSpace)(const SMikkTSpaceContext * pContext, const float fvTangent[], const float fvBiTangent[], const float fMagS, const float fMagT,
+						const tbool bIsOrientationPreserving, const int iFace, const int iVert);
+} SMikkTSpaceInterface;
+
+struct SMikkTSpaceContext
+{
+	SMikkTSpaceInterface * m_pInterface;	// initialized with callback functions
+	void * m_pUserData;						// pointer to client side mesh data etc. (passed as the first parameter with every interface call)
+};
+
+// these are both thread safe!
+tbool genTangSpaceDefault(const SMikkTSpaceContext * pContext);	// Default (recommended) fAngularThreshold is 180 degrees (which means threshold disabled)
+tbool genTangSpace(const SMikkTSpaceContext * pContext, const float fAngularThreshold);
+
+
+// To avoid visual errors (distortions/unwanted hard edges in lighting), when using sampled normal maps, the
+// normal map sampler must use the exact inverse of the pixel shader transformation.
+// The most efficient transformation we can possibly do in the pixel shader is
+// achieved by using, directly, the "unnormalized" interpolated tangent, bitangent and vertex normal: vT, vB and vN.
+// pixel shader (fast transform out)
+// vNout = normalize( vNt.x * vT + vNt.y * vB + vNt.z * vN );
+// where vNt is the tangent space normal. The normal map sampler must likewise use the
+// interpolated and "unnormalized" tangent, bitangent and vertex normal to be compliant with the pixel shader.
+// sampler does (exact inverse of pixel shader):
+// float3 row0 = cross(vB, vN);
+// float3 row1 = cross(vN, vT);
+// float3 row2 = cross(vT, vB);
+// float fSign = dot(vT, row0)<0 ? -1 : 1;
+// vNt = normalize( fSign * float3(dot(vNout,row0), dot(vNout,row1), dot(vNout,row2)) );
+// where vNout is the sampled normal in some chosen 3D space.
+//
+// Should you choose to reconstruct the bitangent in the pixel shader instead
+// of the vertex shader, as explained earlier, then be sure to do this in the normal map sampler also.
+// Finally, beware of quad triangulations. If the normal map sampler doesn't use the same triangulation of
+// quads as your renderer then problems will occur since the interpolated tangent spaces will differ
+// eventhough the vertex level tangent spaces match. This can be solved either by triangulating before
+// sampling/exporting or by using the order-independent choice of diagonal for splitting quads suggested earlier.
+// However, this must be used both by the sampler and your tools/rendering pipeline.
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif