forked from 1b-agent/opencadstudio-upstream
Hakan SevenandClaude Opus 4.7
15bddb2f58
The 5,000 sub-entity guard was added when an xref block with ~74k subs
froze the UI on first render. The block_cache primary path (def72e4)
made that path unreachable for typical Inserts — the guard now only
gated the rare legacy-explode fallback, where it hid otherwise-renderable
geometry as an insertion marker.
Remove the constant and its early-return; the fallback path now matches
the primary path's "render everything" behaviour. Also drop the
RENDERING_OPTIMIZATION.md "TEMPORARY" section that tracked this guard.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
115 lines
3.5 KiB
Markdown
115 lines
3.5 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 2 — Spatial Acceleration Structure
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**Goal:** O(log n) visibility queries instead of O(n) linear scan.
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### 2.1 Quadtree (2D Documents)
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Partition world space into a quadtree keyed by `Aabb2`. Build once on document load, update
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incrementally on entity add/remove/modify.
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```
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QuadTree<EntityId>
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├── query_rect(Aabb2) → Vec<EntityId>
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└── insert / remove / update
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```
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Store in `scene/mod.rs` alongside the entity cache. Invalidate only the nodes touched by a
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modified entity.
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### 2.2 Octree (3D Solids)
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For `MeshModel` / `solid3d` entities, use an octree with `Aabb3` keys. Query returns candidate
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mesh IDs for frustum culling.
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### 2.3 Integration
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Replace linear entity scans in `pipeline/mod.rs` render preparation with spatial queries:
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```rust
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let candidates = scene.quadtree.query_rect(view_aabb);
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// only upload GPU buffers for candidates
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```
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**Estimated gain:** near-constant frame cost regardless of total entity count when zoomed in.
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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 2.1 Quadtree for 2D medium complexity, scales 2D docs
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Phase 2.2 Octree for 3D medium, needed for dense 3D
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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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