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Resolves critical shader composition and format mismatch issues, enabling the
circle mask + rotating cube demonstration at 2.0s-4.0s in the timeline.
**Key Fixes:**
1. **Shader Function Name** (masked_cube.wgsl):
- Fixed call to `ray_box_intersection()` (was incorrectly `ray_box()`)
- Updated return value handling to use `RayBounds` struct (`.hit`, `.t_entry`, `.t_exit`)
- Removed unused `sky_tex` binding to match pipeline layout expectations (5 bindings → 4)
2. **Shader Lifetime Issue** (rotating_cube_effect.h/cc):
- Added `std::string composed_shader_` member to persist shader source
- Prevents use-after-free when WebGPU asynchronously parses shader code
3. **Format Mismatch** (circle_mask_effect.cc):
- Changed compute pipeline format from hardcoded `RGBA8Unorm` to `ctx_.format` (Bgra8UnormSrgb)
- Matches auxiliary texture format created by `MainSequence::register_auxiliary_texture()`
- Added depth stencil state to render pipeline to match scene pass requirements:
* Format: Depth24Plus
* depthWriteEnabled: False (no depth writes needed)
* depthCompare: Always (always pass depth test)
4. **WebGPU Descriptor Initialization** (circle_mask_effect.cc):
- Added `depthSlice = WGPU_DEPTH_SLICE_UNDEFINED` for non-Windows builds
- Ensures proper initialization of render pass color attachments
5. **Test Coverage** (test_demo_effects.cc):
- Updated EXPECTED_SCENE_COUNT: 6 → 8 (added CircleMaskEffect, RotatingCubeEffect)
- Marked both effects as requiring 3D pipeline setup (skipped in basic tests)
**Technical Details:**
- **Auxiliary Texture Flow**: CircleMaskEffect generates mask (1.0 inside, 0.0 outside) →
RotatingCubeEffect samples mask to render only inside circle → GaussianBlurEffect post-processes
- **Pipeline Format Matching**: All pipelines targeting same render pass must use matching formats:
* Color: Bgra8UnormSrgb (system framebuffer format)
* Depth: Depth24Plus (scene pass depth buffer)
- **ShaderComposer Integration**: Relies on `InitShaderComposer()` (called in `gpu.cc:372`)
registering snippets: `common_uniforms`, `math/sdf_utils`, `ray_box`, etc.
**Effect Behavior:**
- Runs from 2.0s to 4.0s in demo timeline
- CircleMaskEffect (priority 0): Draws green outside circle, transparent inside
- RotatingCubeEffect (priority 1): Renders bump-mapped cube inside circle
- GaussianBlurEffect (priority 2): Post-process blur on entire composition
**Test Results:**
- All 33 tests pass (100%)
- No WebGPU validation errors
- Demo runs cleanly with `--seek 2.0`
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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Implements demonstration of auxiliary texture masking system with:
- CircleMaskEffect: Generates circular mask, renders green outside circle
- RotatingCubeEffect: Renders SDF cube inside circle using mask
Architecture:
- Mask generation in compute phase (1.0 inside, 0.0 outside)
- CircleMask renders green where mask < 0.5 (outside circle)
- RotatingCube samples mask and discards where mask < 0.5
Files added:
- src/gpu/effects/circle_mask_effect.{h,cc}
- src/gpu/effects/rotating_cube_effect.{h,cc}
- assets/final/shaders/{circle_mask_compute,circle_mask_render,masked_cube}.wgsl
Build system:
- Updated CMakeLists.txt with new effect sources
- Registered shaders in demo_assets.txt
- Updated test_demo_effects.cc (8 scene effects total)
Status: Effects temporarily disabled in demo.seq (lines 31-35)
- ShaderComposer snippet registration needed for masked_cube.wgsl
- All 33 tests pass, demo runs without crashes
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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