93 lines
4.7 KiB
Markdown
93 lines
4.7 KiB
Markdown
## Render Passes: Background → Geometry → Lighting → Transparent → ImGui
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Pass classes (`IRenderPass`) define initialization and recording logic, but execution is now driven by the Render Graph. Each pass exposes a `register_graph(...)` method to declare dependencies and render targets; the graph handles barriers, layouts, and dynamic rendering.
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### Overview
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- Interface: Each pass implements `IRenderPass { init(context); execute(cmd); cleanup(); getName(); }`. Today, `execute()` is unused for built-in passes; work is recorded via the Render Graph record callback.
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- Manager: `RenderPassManager::init()` creates and stores built-in passes: `BackgroundPass` (compute), `GeometryPass` (G-Buffer), `LightingPass` (deferred), `TransparentPass`, plus optional `ImGuiPass`.
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- Render graph: Passes call `register_graph(graph, ...)` to declare image/buffer access and attachments. The graph inserts barriers and begins/ends dynamic rendering.
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- Shared targets: Passes coordinate through `SwapchainManager` images: `drawImage`, `gBufferPosition/Normal/Albedo`, `depthImage` (imported into the graph each frame).
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- Hot reload: Fetch graphics pipeline/layout by key each frame through `PipelineManager` in the record callback.
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### Quick Start — Add a New Pass (Render Graph)
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```c++
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class MyPass : public IRenderPass {
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public:
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void init(EngineContext* ctx) override {
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_ctx = ctx;
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GraphicsPipelineCreateInfo info{};
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info.vertexShaderPath = _ctx->getAssets()->shaderPath("fullscreen.vert.spv");
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info.fragmentShaderPath = _ctx->getAssets()->shaderPath("my_pass.frag.spv");
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info.setLayouts = { _ctx->getDescriptorLayouts()->gpuSceneDataLayout() };
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info.configure = [this](PipelineBuilder& b){
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b.set_input_topology(VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST);
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b.set_polygon_mode(VK_POLYGON_MODE_FILL);
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b.set_cull_mode(VK_CULL_MODE_NONE, VK_FRONT_FACE_CLOCKWISE);
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b.set_multisampling_none(); b.disable_depthtest();
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b.set_color_attachment_format(_ctx->getSwapchain()->drawImage().imageFormat);
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};
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_ctx->pipelines->createGraphicsPipeline("my_pass", info);
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}
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void register_graph(RenderGraph* graph, RGImageHandle draw, RGImageHandle depth) {
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graph->add_pass(
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"MyPass",
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RGPassType::Graphics,
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[draw, depth](RGPassBuilder& b, EngineContext*) {
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b.write_color(draw);
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b.write_depth(depth, false);
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},
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[this](VkCommandBuffer cmd, const RGPassResources&, EngineContext* ctx){
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VkPipeline p{}; VkPipelineLayout l{};
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ctx->pipelines->getGraphics("my_pass", p, l);
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vkCmdBindPipeline(cmd, VK_PIPELINE_BIND_POINT_GRAPHICS, p);
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VkViewport vp{0,0,(float)ctx->getDrawExtent().width,(float)ctx->getDrawExtent().height,0,1};
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vkCmdSetViewport(cmd, 0, 1, &vp);
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VkRect2D sc{{0,0}, ctx->getDrawExtent()};
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vkCmdSetScissor(cmd, 0, 1, &sc);
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vkCmdDraw(cmd, 3, 1, 0, 0);
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}
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);
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}
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void execute(VkCommandBuffer) override {} // unused with Render Graph
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void cleanup() override {}
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const char* getName() const override { return "MyPass"; }
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private:
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EngineContext* _ctx{};
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};
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// Register in RenderPassManager::init()
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auto myPass = std::make_unique<MyPass>();
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myPass->init(context);
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addPass(std::move(myPass));
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```
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### Built-in Passes
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- Background (compute): Declares `ComputeWrite(drawImage)` and dispatches a selected effect instance.
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- Geometry (G-Buffer): Declares 3 color attachments and `DepthAttachment`, plus buffer reads for shared index/vertex buffers.
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- Lighting (deferred): Reads G‑Buffer as sampled images and writes to `drawImage`.
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- Shadows: Cascaded shadow maps render to per-frame transient depth images (four cascades). If Ray Query is enabled,
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the lighting pass additionally samples TLAS to evaluate shadow visibility according to the selected mode.
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- Transparent (forward): Writes to `drawImage` with depth test against `depthImage` after lighting.
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- ImGui: Inserted just before present to draw on the swapchain image.
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### API Summary
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- `RenderPassManager::addPass(unique_ptr<IRenderPass>)`: Register a new pass (storage/ownership only).
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- `RenderPassManager::setImGuiPass(...)`: Configure the optional ImGui pass.
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- `IRenderPass::register_graph(...)` (per pass class): Declare resources and recording callbacks for the Render Graph.
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### Tips
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- Don’t call `vkCmdBeginRendering` or add manual transitions for declared attachments; the Render Graph handles it.
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- Re-fetch pipeline and layout by key each frame to pick up hot-reloaded shaders.
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- Allocate transient descriptor sets from `currentFrame->_frameDescriptors`; free pass-owned layouts in `cleanup()`.
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- Use `EngineContext::getDrawExtent()` for viewport/scissor.
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See also: `docs/RenderGraph.md` for the builder API and synchronization details.
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