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perf(scene): multi-resolution mesh LOD (Phase 3.4)

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ACIS SAT entities (Solid3D / Region / Body) were tessellated at one
fixed sampling density (CIRC_SEGS=48, GRID_U=32, GRID_V=16) regardless
of how far they were from the camera. Distant solids paid the full
triangle bill for fragments that mostly resolved to sub-pixel size.

Generate three pre-built LODs per entity at load time:

  * LOD 0 (HIGH)  — 48/32/16 segments. Use above 200 px projected diag.
  * LOD 1 (MID)   — 24/16/8.  Use 50–200 px.
  * LOD 2 (LOW)   — 12/8/4.   Use below 50 px.

Tessellation cost is paid 3× on load (cheap — typical files have few
solids). Render picks per-frame via `compute_mesh_lod` from each mesh's
`world_aabb` projected diagonal. When a level is missing (e.g. a solid
entity that only emits LOD 0), the selector walks down to the nearest
available slot.

API ripples:
  * New `LodConfig` (HIGH/MID/LOW) drives `tess_sat`, `tess_cone_face`,
    `tess_sphere_face`, `tess_torus_face`.
  * `tessellate_solid3d / _region / _body` now return `MeshLodSet`.
  * `MeshLodSet { lods: Vec<MeshModel>, world_aabb }` + `from_single`
    constructor so interactive truck-based commands (BOX/CYLINDER/etc.)
    that only generate one tessellation stay one-line.
  * GPU side gets `MeshLodGpu { lods: Vec<MeshGpu>, world_aabb }` and
    a `mesh_lod_levels` per-frame index vector.
  * STL/STEP export pulls slot 0 explicitly so the on-disk geometry
    isn't downgraded by the view-dependent ladder.

Background-thread lazy generation (per the roadmap) is deferred — the
synchronous eager build is fine for typical CAD files. Switch to a
queue + background tessellator when files with hundreds of solids
become a load-time bottleneck.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
Hakan Seven 2026-05-15 23:30:13 +03:00
commit 8c08ae104a
8 changed files with 321 additions and 59 deletions
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5
src/scene/render.rs
View file

@ -14,7 +14,7 @@ use std::sync::Arc;
use super::pipeline::viewcube::{hover_id, VIEWCUBE_PX};
use super::pipeline::Pipeline;
use super::tessellate;
use super::{HatchModel, ImageModel, MeshModel, Scene, Uniforms, WireModel};
use super::{HatchModel, ImageModel, MeshLodSet, Scene, Uniforms, WireModel};
// ── PaperViewportPipeline / PaperViewportPrimitive ────────────────────────
//
@ -86,7 +86,7 @@ pub struct Primitive {
/// Wipeout fills — rendered in a separate pass AFTER wires.
pub(super) wipeout_hatches: Arc<Vec<HatchModel>>,
pub(super) images: Arc<Vec<ImageModel>>,
pub(super) meshes: Arc<Vec<MeshModel>>,
pub(super) meshes: Arc<Vec<MeshLodSet>>,
pub(super) uniforms: Uniforms,
/// Camera rotation matrix derived from the quaternion.
/// Used by the ViewCube pipeline — no gimbal lock.
@ -148,6 +148,7 @@ impl shader::Primitive for Primitive {
pipeline.compute_wipeout_scissors(self.uniforms.view_proj, clip_size.width, clip_size.height);
pipeline.compute_image_scissors(self.uniforms.view_proj, clip_size.width, clip_size.height);
pipeline.compute_hatch_lod(self.uniforms.view_proj, clip_size.width, clip_size.height);
pipeline.compute_mesh_lod(self.uniforms.view_proj, clip_size.width, clip_size.height);
if self.show_viewcube {
pipeline.viewcube.upload(
queue,