192 lines
8.9 KiB
Markdown
192 lines
8.9 KiB
Markdown
## Game‑Facing API Overview
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This document summarizes the main engine APIs that are directly useful when building a game (spawn actors, control lights/animations, and interact via picking).
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For details on the underlying systems, see also:
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- `docs/Scene.md` – cameras, draw context, instances, picking.
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- `docs/EngineContext.md` – access to managers and per‑frame state.
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- `docs/RenderGraph.md` – render‑graph API for custom passes.
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---
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## VulkanEngine Helpers
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Header: `src/core/engine.h`
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- Lifecycle
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- `void init()` – initialize SDL, device, managers, scene, render graph.
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- `void run()` – main loop: handles events, updates scene, builds Render Graph, submits frames.
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- `void cleanup()` – destroy managers and GPU resources.
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- GLTF spawn helper
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- `bool addGLTFInstance(const std::string &instanceName, const std::string &modelRelativePath, const glm::mat4 &transform = glm::mat4(1.f));`
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- Loads a glTF from `assets/models/...` (via `AssetManager`) and registers it as a runtime scene instance.
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- `instanceName` becomes the logical name used by `SceneManager` (e.g. for picking and animation control).
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- Picking access
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- `struct PickInfo` (nested in `VulkanEngine`)
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- `MeshAsset *mesh`, `LoadedGLTF *scene`, `Node *node`
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- `RenderObject::OwnerType ownerType` (e.g. `StaticGLTF`, `GLTFInstance`, `MeshInstance`)
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- `std::string ownerName`
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- `glm::vec3 worldPos`
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- `glm::mat4 worldTransform`
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- `uint32_t indexCount`, `firstIndex`, `surfaceIndex`
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- `bool valid`
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- `const PickInfo &get_last_pick() const`
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- Returns the last click selection result.
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- Filled by the engine from either CPU ray picking or ID‑buffer picking depending on `_useIdBufferPicking`.
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- Typical usage:
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- On mouse‑up in your game layer, read `engine->get_last_pick()` and, if `valid`, use `ownerName`/`worldPos` to drive selection logic.
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> Note: hover picks and drag selections are also available as internal fields on `VulkanEngine` (`_hoverPick`, `_dragSelection`) and are documented in `docs/Scene.md`. You can expose additional getters if you want to rely on them from game code.
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---
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## Scene & Instances (Actors, Lights, Animations)
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Header: `src/scene/vk_scene.h`
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Docs: `docs/Scene.md`
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### Dynamic Mesh/GLTF Instances
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- Mesh instances
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- `void addMeshInstance(const std::string &name, std::shared_ptr<MeshAsset> mesh, const glm::mat4 &transform = glm::mat4(1.f), std::optional<BoundsType> boundsType = {});`
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- `bool getMeshInstanceTransform(const std::string &name, glm::mat4 &outTransform);`
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- `bool setMeshInstanceTransform(const std::string &name, const glm::mat4 &transform);`
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- `bool removeMeshInstance(const std::string &name);`
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- `void clearMeshInstances();`
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- Typical usage:
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- Spawn primitives or dynamic meshes at runtime (e.g. projectiles, props).
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- Use `setMeshInstanceTransform` every frame to move them based on game logic.
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- GLTF instances (actors)
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- `void addGLTFInstance(const std::string &name, std::shared_ptr<LoadedGLTF> scene, const glm::mat4 &transform = glm::mat4(1.f));`
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- `bool getGLTFInstanceTransform(const std::string &name, glm::mat4 &outTransform);`
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- `bool setGLTFInstanceTransform(const std::string &name, const glm::mat4 &transform);`
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- `bool removeGLTFInstance(const std::string &name);`
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- `void clearGLTFInstances();`
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- Usage pattern:
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- Treat each GLTF instance as an “actor” with a name; use transforms to place characters, doors, props, etc.
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### Animations (GLTF)
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- Scene‑level
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- `bool setSceneAnimation(const std::string &sceneName, int animationIndex, bool resetTime = true);`
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- `bool setSceneAnimation(const std::string &sceneName, const std::string &animationName, bool resetTime = true);`
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- `bool setSceneAnimationLoop(const std::string &sceneName, bool loop);`
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- Instance‑level
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- `bool setGLTFInstanceAnimation(const std::string &instanceName, int animationIndex, bool resetTime = true);`
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- `bool setGLTFInstanceAnimation(const std::string &instanceName, const std::string &animationName, bool resetTime = true);`
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- `bool setGLTFInstanceAnimationLoop(const std::string &instanceName, bool loop);`
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- Notes:
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- All functions return `bool` indicating whether the named scene/instance exists.
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- Animation state is **independent per scene and per instance**:
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- Each named scene has its own `AnimationState`.
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- Each glTF instance has its own `AnimationState`, even when sharing the same `LoadedGLTF`.
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- An index `< 0` (e.g. `-1`) disables animation for that scene/instance (pose is frozen at the last evaluated state).
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- `SceneManager::update_scene()` advances each active animation state every frame using engine delta time.
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### Per‑Instance Node / Joint Control (Non‑Skinned)
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For rigid models and simple “joints” (e.g. flaps, doors, turrets), you can apply local‑space pose offsets to individual glTF nodes per instance:
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- `bool setGLTFInstanceNodeOffset(const std::string &instanceName, const std::string &nodeName, const glm::mat4 &offset);`
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- `bool clearGLTFInstanceNodeOffset(const std::string &instanceName, const std::string &nodeName);`
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- `void clearGLTFInstanceNodeOffsets(const std::string &instanceName);`
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Typical usage:
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- Use glTF animation for the base motion (e.g. gear deployment).
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- Layer game‑driven offsets on top for per‑instance control:
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```cpp
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// Rotate a control surface on one aircraft instance
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glm::mat4 offset =
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glm::rotate(glm::mat4(1.f),
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glm::radians(aileronDegrees),
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glm::vec3(1.f, 0.f, 0.f));
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sceneMgr->setGLTFInstanceNodeOffset("plane01", "LeftAileron", offset);
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```
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### Point Lights
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- Struct:
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- `struct PointLight { glm::vec3 position; float radius; glm::vec3 color; float intensity; };`
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- API:
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- `void addPointLight(const PointLight &light);`
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- `void clearPointLights();`
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- `size_t getPointLightCount() const;`
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- `bool getPointLight(size_t index, PointLight &outLight) const;`
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- `bool setPointLight(size_t index, const PointLight &light);`
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- `bool removePointLight(size_t index);`
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- Typical usage:
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- On level load, add all static lights.
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- At runtime, animate or toggle lights based on gameplay events (e.g. explosions, flickering lamps).
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---
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## Picking & Selection (Interaction)
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Picking lives in `SceneManager` and is wired into `VulkanEngine`’s frame loop.
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Header: `src/scene/vk_scene.h`
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Implementation: `src/scene/vk_scene_picking.cpp`
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### Single‑Object Ray Picking
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- `bool pick(const glm::vec2 &mousePosPixels, RenderObject &outObject, glm::vec3 &outWorldPos);`
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- Input:
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- `mousePosPixels` – window coordinates (SDL style), origin at top‑left.
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- Output on success:
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- `outObject` – closest `RenderObject` hit by the camera ray.
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- `outWorldPos` – precise world‑space hit position (uses mesh BVH when available).
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- Returns:
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- `true` if any object was hit, otherwise `false`.
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### ID‑Buffer Picking
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- `bool resolveObjectID(uint32_t id, RenderObject &outObject) const;`
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- Takes an ID read back from the ID buffer and resolves it to the corresponding `RenderObject` in the latest `DrawContext`.
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- Used by the engine when `_useIdBufferPicking` is enabled to implement asynchronous picking.
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### Rectangle Selection (Drag Box)
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- `void selectRect(const glm::vec2 &p0, const glm::vec2 &p1, std::vector<RenderObject> &outObjects) const;`
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- Inputs:
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- `p0`, `p1` – opposite corners of a window‑space rectangle (top‑left origin).
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- Output:
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- `outObjects` – appended with all `RenderObject`s whose projected bounds intersect the rectangle.
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- Internals:
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- Uses `sceneData.viewproj` and an NDC‑space bounds test to determine overlap.
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### Typical Game Usage
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- Hover tooltips:
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- Track mouse position in window coordinates.
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- Use `SceneManager::pick` directly, or read `VulkanEngine::get_last_pick()` and/or `_hoverPick` as documented in `Scene.md`.
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- Object selection / interaction:
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- On mouse click release, inspect `engine->get_last_pick()`:
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- If `valid`, dispatch interaction based on `ownerType` / `ownerName` (e.g. select unit, open door).
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- Multi‑select:
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- When implementing drag selection, call `SceneManager::selectRect` with the drag rectangle to get all hits, or reuse the engine’s `_dragSelection` mechanism.
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---
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## ImGui / ImGuizmo Editor Utilities
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File: `src/core/engine_ui.cpp`
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These are primarily debug/editor features but can be kept in a game build to provide in‑game tools.
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- Main entry:
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- `void vk_engine_draw_debug_ui(VulkanEngine *eng);`
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- Called once per frame by the engine to build the “Debug” window tabs.
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- Useful tools for games:
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- Scene tab:
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- Spawn glTF instances at runtime using `VulkanEngine::addGLTFInstance(...)`.
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- Spawn primitive mesh instances (cube/sphere) using `SceneManager::addMeshInstance(...)`.
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- Point‑light editor UI built on `SceneManager` light APIs.
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- Object gizmo (ImGuizmo):
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- Uses last pick / hover pick as the current target and manipulates transforms via `setMeshInstanceTransform` / `setGLTFInstanceTransform`.
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