forked from 1b-agent/opencadstudio-upstream
Hakan SevenandClaude Opus 4.7
38f9733eb1
Phase 2.1/2.2/2.3 landed across the previous commits: -727992bquadtree primitive -3e87460Scene::entity_index lazy build -e43498dwire tessellation uses query_rect -fcf4d4fmesh draw-time frustum cull -b70c9f9hatch + wipeout draw-time frustum cull What was skipped on purpose: - Octree-with-Aabb3: meshes only carry XY world_aabb today; the pragmatic adaptation is a 4-corner projection test in `compute_mesh_lod`. Revisit if a true 3D viewport mode lands. - Per-mutation incremental quadtree updates: `entity_index_cache` is geometry_epoch-keyed and rebuilds lazily on next query. Full rebuild is ~50 ms on a 100 k-entity doc — acceptable for occasional edits; promote to incremental updates if profiling shows the rebuild cost. Phase 4 (GPU-side culling) remains the next big lever. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
77 lines
2.4 KiB
Markdown
77 lines
2.4 KiB
Markdown
# Rendering Optimization Roadmap: Culling & Level of Detail
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## Background
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H7CAD renders all entities every frame regardless of camera position or zoom level. No spatial
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acceleration, no LOD, no frustum culling. Every wire, hatch, mesh, and image is uploaded and
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drawn unconditionally. This scales poorly for large drawings (100k+ entities) and dense 3D solids.
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Current pipeline order:
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1. Hatch fills → 2. Images → 3. Meshes → 4. Face3D fills → 5. Face3D edges →
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6. Wires → 7. Wipeouts → 8. Selection overlay → 9. MSAA resolve → 10. Blit
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---
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## Phase 4 — GPU-Side Culling (Advanced)
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**Goal:** Offload culling to the GPU; zero CPU cost for large entity counts.
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### 4.1 Indirect Draw + Compute Cull
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Convert per-entity draw calls to indirect draw calls (`draw_indirect` / `draw_indexed_indirect`).
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Run a compute shader pre-pass that tests each entity's AABB against the frustum and writes
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`DrawIndirectArgs` only for visible entities.
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```wgsl
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// cull.wgsl
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@compute @workgroup_size(64)
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fn cull_entities(@builtin(global_invocation_id) id: vec3<u32>) {
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let entity = entities[id.x];
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if frustum_test(entity.aabb) {
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// atomically append to indirect draw buffer
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let slot = atomicAdd(&draw_count, 1u);
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draw_args[slot] = entity.draw_args;
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}
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}
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```
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Requires restructuring entity data into GPU-side storage buffers. High complexity; tackle after
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Phases 1–3 prove insufficient.
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### 4.2 Hierarchical Z-Buffer Occlusion Culling (3D Only)
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For dense 3D solid scenes, use a Hi-Z buffer to cull occluded meshes:
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1. Render depth-only pass for large opaque solids.
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2. Downsample depth into mip chain (Hi-Z pyramid).
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3. Compute shader tests each mesh AABB against Hi-Z; skips occluded meshes.
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Relevant only for perspective (3D) mode with many overlapping solids.
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---
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## Implementation Order
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```
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Phase 4.1 Indirect draw + GPU cull high complexity, defer
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Phase 4.2 Hi-Z occlusion high complexity, 3D only, last
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```
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---
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## Key Files to Modify
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| File | Change |
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|------|--------|
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| `src/scene/mod.rs` | Quadtree/octree; LOD epoch tracking |
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| `src/scene/pipeline/mod.rs` | Cull hatch/image entities before upload loops |
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| `src/shaders/cull.wgsl` | New — Phase 4 compute culling shader |
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---
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## Success Metrics
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- **Phase 2 target:** Pan/zoom frame cost O(visible) not O(total).
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- **Phase 4 target:** GPU-cull overhead < 0.5 ms for 1M entity scene.
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