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perf(scene): zoom-adaptive curve tolerance for top-level wires (Phase 3.2)

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Edge tessellation used a fixed 0.005 world-unit chord-height tolerance
regardless of zoom — a 1000 m radius arc viewed at 50 mm/px still emitted
hundreds of segments that all collapsed onto the same screen pixel.

`truck_tess` now reads tolerance from a process-wide AtomicU64 override.
`Scene::wires_for_block` sets the override to ~0.5 px chord height
(world_per_pixel × 0.5) before the par_iter, then a Drop guard clears it
back to the default. Floor stays at the original CURVE_TOL so extreme
zoom-in keeps full quality. Block-cache rebuilds and off-render paths
(snap, hit-test) always see the default — the override is bracketed to
the render call only.

Roadmap entry for Phase 3.2 removed; Implementation Order / Key Files
tables updated.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
Hakan 2026-05-15 14:07:28 +03:00
commit 26271b8c63
3 changed files with 50 additions and 29 deletions
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27
RENDERING_OPTIMIZATION.md
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@ -64,31 +64,6 @@ let candidates = scene.quadtree.query_rect(view_aabb);
**Goal:** Reduce geometric complexity when entities are small or far away.
### 3.2 Wire LOD — Curve Segment Reduction
Arcs, ellipses, and splines tessellate to N segments (currently fixed). Replace with
zoom-adaptive segment count.
```rust
fn arc_segments(radius_world: f64, px_per_unit: f64) -> u32 {
// target: ~1 segment per 2px of arc length on screen
let arc_px = radius_world * px_per_unit * TWO_PI;
(arc_px / 2.0).clamp(8.0, 256.0) as u32
}
```
Recompute segments when zoom crosses a threshold (epoch-based invalidation already in place).
Store LOD level per entity; retessellate only on LOD level change.
LOD levels (example):
| Zoom (px/unit) | Segments per 90° arc |
|----------------|----------------------|
| > 100 px/u | 64 (full detail) |
| 10–100 px/u | 24 |
| 1–10 px/u | 12 |
| < 1 px/u | 6 (or sub-pixel cull)|
### 3.3 Hatch LOD — Density Reduction
At low zoom, hatch line spacing appears smaller than 1px. Options:
@ -163,7 +138,6 @@ Relevant only for perspective (3D) mode with many overlapping solids.
```
Phase 1.4 Scissor for hatch/image low complexity
Phase 2.1 Quadtree for 2D medium complexity, scales 2D docs
Phase 3.2 Wire curve LOD medium, affects tessellation cache
Phase 3.3 Hatch LOD low complexity
Phase 3.4 Mesh LOD high complexity, background thread
Phase 2.2 Octree for 3D medium, needed for dense 3D
@ -180,7 +154,6 @@ Phase 4.2 Hi-Z occlusion high complexity, 3D only, last
| `src/scene/mesh_model.rs` | Add `Aabb3`, LOD mesh array |
| `src/scene/hatch_model.rs` | Add `Aabb2` field |
| `src/scene/image_model.rs` | Add `Aabb2` field |
| `src/scene/tessellate.rs` | Adaptive arc segments |
| `src/scene/truck_tess.rs` | Multi-resolution mesh tessellation |
| `src/scene/mod.rs` | Quadtree/octree; LOD epoch tracking |
| `src/scene/pipeline/mod.rs` | Cull hatch/image entities before upload loops |