feat: WGSL Uniform Buffer Validation & Consolidation (Task #75)

- Added  to validate WGSL/C++ struct alignment.
- Integrated validation into .
- Standardized uniform usage in , , , .
- Renamed generic  to specific names in WGSL and C++ to avoid collisions.
- Added  and updated .
- handoff(Gemini): Completed Task #75.

1 files changed, 106 insertions, 0 deletions

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+# WGSL Uniform Buffer Guidelines
+
+This document outlines the rules and best practices for defining and using uniform buffers in WGSL shaders within this project, focusing on alignment, size, and consistency.
+
+## WGSL Alignment Rules
+
+Understanding WGSL's memory layout rules is crucial for correct uniform buffer implementation. The following are the general alignment requirements for common WGSL types:
+
+- `f32`: 4-byte alignment.
+- `vec2<f32>`: 8-byte alignment (4 bytes per component * 2 components = 8 bytes).
+- `vec3<f32>`: 16-byte alignment (4 bytes per component * 3 components = 12 bytes, padded to 16).
+- `vec4<f32>`: 16-byte alignment (4 bytes per component * 4 components = 16 bytes).
+- `array<T, N>`: The alignment of an array is typically the alignment of its base type `T`.
+
+Structs are padded to the alignment of their largest member. Any trailing space in a struct is also padded to match the maximum alignment of any member within the struct.
+
+## Standard Uniform Buffer Pattern
+
+To maintain consistency and facilitate efficient rendering, a standard pattern for uniform buffer usage is established:
+
+- **Binding 0 & 1:** Reserved for Sampler and Texture access (handled by `pp_update_bind_group`).
+- **Binding 2:** **Common Uniforms** (`CommonPostProcessUniforms` or similar). This buffer should contain frequently used data like resolution, aspect ratio, time, beat, and audio intensity.
+- **Binding 3:** **Effect-Specific Parameters**. This buffer holds parameters unique to a particular effect (e.g., `strength`, `speed`, `fade_amount`).
+
+This pattern ensures that common data is shared efficiently across effects, while effect-specific data remains isolated.
+
+## Defining Uniform Structs
+
+### WGSL Definitions
+
+When defining uniform structs in WGSL, adhere to the following:
+
+- **Explicit Padding:** Use padding fields (`_pad0`, `_pad1`, etc.) where necessary to ensure correct alignment, especially when mixing types of different alignment requirements (e.g., `vec2<f32>` followed by `f32`s).
+- **Use `vec2<f32>` for 8-byte padding:** If you need 8 bytes of padding, use `_pad0: vec2<f32>` instead of `_pad0: f32, _pad1: f32` for potentially better clarity and to leverage WGSL's type system.
+- **Minimize Padding:** Only add padding where required by alignment rules to reduce memory usage.
+
+**Example (CommonPostProcessUniforms / HeptagonUniforms):**
+
+```wgsl
+struct CommonUniforms {
+  resolution: vec2<f32>,
+  _pad0: vec2<f32>, // 8 bytes padding to align subsequent members
+  aspect_ratio: f32,
+  time: f32,
+  beat: f32,
+  audio_intensity: f32,
+};
+// Expected size: 32 bytes
+```
+
+**Example (EffectParams with f32 members):**
+
+```wgsl
+struct EffectParams {
+  parameter1: f32,
+  parameter2: f32,
+  // ... more parameters ...
+};
+// Expected size: 8 bytes (if only two f32s)
+```
+
+### C++ Definitions and Validation
+
+For every WGSL uniform struct, a corresponding C++ struct must exist. This C++ struct must include a `static_assert` to verify its size and alignment matches the WGSL definition.
+
+- **Mirror WGSL Structure:** The C++ struct should mirror the WGSL struct's member order and types as closely as possible to ensure accurate size calculation.
+- **`static_assert`:** Always include `static_assert(sizeof(MyStruct) == EXPECTED_SIZE, "MyStruct must be EXPECTED_SIZE bytes for WGSL alignment");`.
+- **Use `float` for `f32`:** Use `float` for `f32` in C++.
+- **Use `vec2<f32>` mapping:** If WGSL uses `vec2<f32>`, map it to an equivalent C++ type that occupies 8 bytes, typically `float[2]` or a `struct Vec2 { float x, y; }` if more complex type handling is needed.
+- **Padding:** C++ padding rules can differ from WGSL. Pay close attention to `static_assert` for validation.
+
+**Example (C++ CommonPostProcessUniforms):**
+
+```cpp
+struct CommonPostProcessUniforms {
+  vec2 resolution;    // 8 bytes
+  float _pad[2];      // 8 bytes padding (matches vec2<f32> in WGSL)
+  float aspect_ratio; // 4 bytes
+  float time;         // 4 bytes
+  float beat;         // 4 bytes
+  float audio_intensity; // 4 bytes
+};
+static_assert(sizeof(CommonPostProcessUniforms) == 32, 
+              "CommonPostProcessUniforms must be 32 bytes for WGSL alignment");
+```
+
+**Example (C++ GaussianBlurParams):**
+
+```cpp
+struct GaussianBlurParams {
+  float strength = 2.0f;
+  float _pad = 0.0f;
+};
+static_assert(sizeof(GaussianBlurParams) == 8, 
+              "GaussianBlurParams must be 8 bytes for WGSL alignment");
+```
+
+## Handling Common Pitfalls
+
+- **`vec3<f32>` Padding:** Avoid using `vec3<f32>` for padding in WGSL, as it has a 16-byte alignment. If padding is needed, use `vec2<f32>` for 8 bytes or individual `f32`s for 4-byte alignment.
+- **C++ vs. WGSL Alignment:** Always rely on `static_assert` in C++ and verify against WGSL alignment rules. C++ padding rules might differ, and the `static_assert` is the ultimate arbiter.
+- **Unmatched Structs:** Ensure every WGSL uniform struct has a corresponding C++ struct with a matching `static_assert`.
+
+## Validation Tool
+
+The `tools/validate_uniforms.py` script is integrated into the build system. It automatically checks for inconsistencies between WGSL and C++ uniform struct definitions and reports any size mismatches. Ensure this script passes for all new or modified uniform definitions.