re-org en App

lib/src/shaders/README.md

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+# Shaders Directory
+
+## Overview
+
+Contains WGSL shader source files used by the PipelineCache module. These are loaded at runtime from disk when referenced by their registered ID in PipelineCache.register_shader(). If a file is missing, PipelineCache falls back to the embedded BASIC_SHADER constant defined in utils::conf.
+
+| File | Purpose |
+|------|---------|
+| **basic_shader.wgsl** | Default vertex/fragment shader pair (vs_main / fs_main entry points) with position, normal, UV, and color attributes matching the Vertex struct layout. |
+
+## Shader Contract
+
+The WGSL shader must define:
+
+- `@vertex fn vs_main() -> @builtin(position) vec4<f32>` — vertex entry point
+- `@fragment fn fs_main() -> @location(0) vec4<f32>` — fragment entry point writing RGBA output
+- Vertex input attributes matching the 56-byte stride of resources::Vertex:
+  - `@location(0)` → position `[f32; 3]` (offset 0)
+  - `@location(1)` → normal `[f32; 3]` (offset 12)
+  - `@location(2)` → uv `[f32; 2]` (offset 24)
+  - `@location(3)` → color `[f32; 4]` (offset 32)

lib/src/shaders/basic_shader.wgsl

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+//! # Basic Shader Module
+struct VertexInput {
+    @location(0) position: vec3<f32>,
+    @location(1) uv: vec2<f32>,
+    @location(2) color: vec3<f32>,
+};
+
+struct VertexOutput {
+    @builtin(position) clip_position: vec4<f32>,
+    @location(0) color: vec3<f32>,
+};
+
+@vertex
+fn vs_main(model: VertexInput) -> VertexOutput {
+    var out: VertexOutput;
+    out.clip_position = vec4<f32>(model.position, 1.0);
+    out.color = model.color; // On transmet la couleur au fragment shader
+    return out;
+}
+
+@fragment
+fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
+    return vec4<f32>(in.color, 1.0);
+}