forked from 1b-agent/opencadstudio-upstream
Hakan SevenandClaude Opus 4.7
66fca6e591
Phase 4-B (batched hatch pipeline) is in; Phase 4.1 (multi-draw indirect / GPU compute cull) stays as a deliberate non-goal because iced 0.14 doesn't expose the required wgpu features to widget pipelines, and the single-draw batched path already collapses N bind-group swaps + N draw calls into one. Phase 4.2 (Hi-Z occlusion) only matters for perspective 3D, which H7CAD doesn't ship. The doc is now a short stub — the per-phase rationale lives at the call sites (search for "Phase N.X" comments). Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
40 lines
2.0 KiB
Markdown
40 lines
2.0 KiB
Markdown
# Rendering Optimization Roadmap
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Phases 1–4 have all landed. This document is kept as a stub so the
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git history points somewhere; the optimisations themselves are
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documented inline at the call sites:
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- **Phase 1** – per-frame LOD ladder, scissor cull (search for
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`Phase 1.*` in `scene/pipeline/mod.rs`).
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- **Phase 2** – quadtree spatial index for top-level entities, plus
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draw-time frustum cull for hatches / wipeouts / meshes
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(`Phase 2.1`, `2.2`, `2.3`).
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- **Phase 3** – LOD substitution for far / sub-pixel content
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(`Phase 3.2`, `3.3`, `3.4`).
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- **Phase 4-B** – batched hatch pipeline. Every hatch is uploaded
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into shared storage buffers (`hatch_batched_gpu.rs`) and drawn in
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one `pass.draw(0..6N, 0..1)`; the per-instance `visibility` buffer
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doubles as a CPU-driven cull mask (sub-pixel + frustum) that the
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vertex shader honours by emitting an out-of-NDC clip position for
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skipped instances. Replaces N bind-group swaps + N draw calls with
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a single draw.
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## Deliberate non-goals
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- **Phase 4.1 (multi-draw indirect / compute cull)** — iced 0.14
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doesn't expose `Features::MULTI_DRAW_INDIRECT` to widget pipelines.
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Without it, single-draw indirect adds no real saving over the
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current batched draw. Revisit if iced surfaces the feature flag,
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or if H7CAD ever swaps the shader widget for a custom wgpu surface.
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- **Phase 4.2 (Hi-Z occlusion)** — pays off only for perspective 3D
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with many overlapping opaque meshes. H7CAD is orthographic
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top-down for every realistic workflow, so the win is theoretical.
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- **Per-mutation incremental quadtree updates** — `entity_index_cache`
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rebuilds lazily on `geometry_epoch` change. Full rebuild is ~50 ms
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on a 100 k-entity doc; promote to per-mutation `insert`/`remove`/
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`update` if profiling shows that as a hot spot during heavy edits.
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- **Per-hatch viewport scissor in the batched path** — paper-space
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MSPACE viewports can render hatches past the viewport border for
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now. Add a per-instance scissor rect (computed from `vp_scissor`)
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if it shows up as a visible artefact.
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