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Reuse mesh for untouched CSG edits

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This commit is contained in:
Meta Vens 2026-05-07 15:39:31 +01:00
commit 672432f671
5 changed files with 121 additions and 32 deletions
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14
docs/csg-performance-fixtures.md
View file

@ -130,6 +130,12 @@ suffix. The result is parity-checked against a full rebuild. Cache validity is
tracked as a prefix boundary so repeated edits do not deep-copy stale
checkpoints. Final mesh emission is still whole-output.
Mesh reuse seam: incremental rebuilds now keep the previous generation's cached
mesh and reuse it only when suffix replay proves no geometry was touched. This
is intentionally exact and conservative: distant rejected edits can skip mesh
emission, while candidate cuts still emit the full output mesh. The report
exposes `reused_mesh` so the fixture and tests do not infer reuse from timing.
## Latest Local Baseline
Captured on 2026-05-07 with `.\tools\run_csg_perf.ps1 -UseRealtimeCsgCpp`:
@ -190,7 +196,9 @@ falls back to full replay only when no valid checkpoint exists.
Tail-edit lesson: prefix caching cuts the room-grid dirty mean by roughly 7.8x,
the rotated-stack dirty mean by roughly 8.4x, the common-box chain by roughly
48x, and the distant-cutter case by roughly 39x. The single-cut case is still
48x, and the distant-cutter case by roughly 39x in this run. A follow-up mesh
reuse seam pushed distant rejected edits into low microseconds by reusing the
previous mesh when no geometry was touched. The single-cut case is still
slightly slower because cache machinery dominates. The next hard target is
cached mesh emission or dirty output patching; replaying less CSG work is not
enough if every edit still serializes the whole result mesh.
dirty mesh range patching for candidate edits; replaying less CSG work is not
enough when every real cut still serializes the whole result mesh.

8
examples/csg_perf_fixture.rs
View file

@ -110,6 +110,7 @@ fn run_case(case: PerfCase, mode: PerfMode) {
let mut warnings = 0;
let mut candidate_pairs = 0;
let mut rejected_pairs = 0;
let mut reused_mesh = false;
for iteration in 0..MEASURE_ITERS {
let start = Instant::now();
@ -120,12 +121,14 @@ fn run_case(case: PerfCase, mode: PerfMode) {
warnings = output.report.warnings.len();
candidate_pairs = output.report.candidate_pairs;
rejected_pairs = output.report.rejected_pairs;
reused_mesh = output.report.reused_mesh;
black_box((
triangles,
fragments,
warnings,
candidate_pairs,
rejected_pairs,
reused_mesh,
));
timings.push(elapsed);
}
@ -141,7 +144,7 @@ fn run_case(case: PerfCase, mode: PerfMode) {
let p95_ns = percentile_ns(&timings, 95);
println!(
"{{\"kernel\":\"vg_csg\",\"mode\":\"{}\",\"scenario\":\"{}\",\"brushes\":{},\"iterations\":{},\"warmup_iterations\":{},\"mean_ns\":{},\"min_ns\":{},\"p50_ns\":{},\"p95_ns\":{},\"max_ns\":{},\"triangles\":{},\"fragments\":{},\"warnings\":{},\"candidate_pairs\":{},\"rejected_pairs\":{}}}",
"{{\"kernel\":\"vg_csg\",\"mode\":\"{}\",\"scenario\":\"{}\",\"brushes\":{},\"iterations\":{},\"warmup_iterations\":{},\"mean_ns\":{},\"min_ns\":{},\"p50_ns\":{},\"p95_ns\":{},\"max_ns\":{},\"triangles\":{},\"fragments\":{},\"warnings\":{},\"candidate_pairs\":{},\"rejected_pairs\":{},\"reused_mesh\":{}}}",
mode.as_str(),
case.name,
case.brushes,
@ -156,7 +159,8 @@ fn run_case(case: PerfCase, mode: PerfMode) {
fragments,
warnings,
candidate_pairs,
rejected_pairs
rejected_pairs,
reused_mesh
);
}

125
src/assembler.rs
View file

@ -15,13 +15,14 @@ pub enum BuildWarning {
IntersectIgnoredForNonBox { brush: String },
}
#[derive(Clone, Debug, Default)]
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct BuildReport {
pub input_brushes: usize,
pub emitted_convex_fragments: usize,
pub operator_brushes: usize,
pub candidate_pairs: usize,
pub rejected_pairs: usize,
pub reused_mesh: bool,
pub warnings: Vec<BuildWarning>,
}
@ -88,7 +89,7 @@ struct BoxBuildCache {
checkpoints: Vec<BoxBuildState>,
}
#[derive(Clone, Debug, Default)]
#[derive(Clone, Debug, Default, PartialEq)]
struct BoxBuildState {
boxes: Vec<(Aabb, MaterialId)>,
report: BuildReport,
@ -101,7 +102,7 @@ struct GeneralBuildCache {
checkpoints: Vec<GeneralBuildState>,
}
#[derive(Clone, Debug, Default)]
#[derive(Clone, Debug, Default, PartialEq)]
struct GeneralBuildState {
mesh: TriangleMesh,
solids: Vec<ConvexSolid>,
@ -157,7 +158,6 @@ impl Assembler {
self.compiled.push(CompiledBrush::from_brush(&brush));
self.brushes.push(brush);
self.generation = self.generation.wrapping_add(1);
self.cache.borrow_mut().take();
self.mark_dirty_index(index);
id
}
@ -170,7 +170,6 @@ impl Assembler {
self.brushes[index].set_dirty();
self.compiled[index] = CompiledBrush::from_brush(&self.brushes[index]);
self.generation = self.generation.wrapping_add(1);
self.cache.borrow_mut().take();
self.mark_dirty_index(index);
true
}
@ -183,7 +182,6 @@ impl Assembler {
self.brushes[index].set_dirty();
self.compiled[index] = CompiledBrush::from_brush(&self.brushes[index]);
self.generation = self.generation.wrapping_add(1);
self.cache.borrow_mut().take();
self.mark_dirty_index(index);
true
}
@ -452,6 +450,7 @@ impl Assembler {
}
let brush_count = self.compiled.len();
let previous_output = self.cache.borrow().as_ref().cloned();
let rebuild_from = match first_dirty_index {
Some(index) => index.min(brush_count),
None => self
@ -479,8 +478,9 @@ impl Assembler {
let mut checkpoints = (start_index == 0).then(|| vec![BoxBuildState::default()]);
let mut changed_geometry = start_index == 0;
for brush in &self.compiled[start_index..] {
state.apply_compiled_box(brush);
changed_geometry |= state.apply_compiled_box(brush);
if let Some(checkpoints) = &mut checkpoints {
checkpoints.push(state.clone());
}
@ -497,11 +497,16 @@ impl Assembler {
cache.valid_checkpoint_index = cache.valid_checkpoint_index.min(start_index);
}
Some(state.into_output(self.brushes.len(), self.generation))
let reused_mesh = (!changed_geometry)
.then_some(previous_output)
.flatten()
.map(|output| output.mesh);
Some(state.into_output_with_mesh(self.brushes.len(), self.generation, reused_mesh))
}
fn build_general_from_cache(&self, first_dirty_index: Option<usize>) -> BuildOutput {
let brush_count = self.compiled.len();
let previous_output = self.cache.borrow().as_ref().cloned();
let rebuild_from = match first_dirty_index {
Some(index) => index.min(brush_count),
None => self
@ -529,8 +534,9 @@ impl Assembler {
let mut checkpoints = (start_index == 0).then(|| vec![GeneralBuildState::default()]);
let mut changed_geometry = start_index == 0;
for brush in &self.compiled[start_index..] {
state.apply_compiled_brush(brush);
changed_geometry |= state.apply_compiled_brush(brush);
if let Some(checkpoints) = &mut checkpoints {
checkpoints.push(state.clone());
}
@ -547,7 +553,11 @@ impl Assembler {
cache.valid_checkpoint_index = cache.valid_checkpoint_index.min(start_index);
}
state.into_output(self.brushes.len(), self.generation)
let reused_mesh = (!changed_geometry)
.then_some(previous_output)
.flatten()
.map(|output| output.mesh);
state.into_output_with_mesh(self.brushes.len(), self.generation, reused_mesh)
}
pub fn sample_room_with_door() -> Self {
@ -649,18 +659,21 @@ impl CompiledBrush {
}
impl BoxBuildState {
fn apply_compiled_box(&mut self, brush: &CompiledBrush) {
fn apply_compiled_box(&mut self, brush: &CompiledBrush) -> bool {
let CompiledGeometry::Box(bounds) = brush.geometry else {
unreachable!("box build state received a non-box brush");
};
match brush.op {
BrushOp::Add => self.boxes.push((bounds, brush.material)),
BrushOp::Add => {
self.boxes.push((bounds, brush.material));
true
}
BrushOp::Subtract => {
self.report.operator_brushes += 1;
if !bounds.intersects_any(self.boxes.iter().map(|(bounds, _)| *bounds)) {
self.report.rejected_pairs += self.boxes.len();
return;
return false;
}
let mut out = Vec::with_capacity(self.boxes.len() + 4);
@ -679,13 +692,15 @@ impl BoxBuildState {
}
}
self.boxes = out;
true
}
BrushOp::Intersect => {
self.report.operator_brushes += 1;
if !bounds.intersects_any(self.boxes.iter().map(|(bounds, _)| *bounds)) {
let changed = !self.boxes.is_empty();
self.report.rejected_pairs += self.boxes.len();
self.boxes.clear();
return;
return changed;
}
self.boxes = self
@ -701,16 +716,27 @@ impl BoxBuildState {
}
})
.collect();
true
}
}
}
fn into_output(mut self, input_brushes: usize, generation: u64) -> BuildOutput {
fn into_output_with_mesh(
mut self,
input_brushes: usize,
generation: u64,
reused_mesh: Option<TriangleMesh>,
) -> BuildOutput {
let mut mesh = TriangleMesh::new();
self.report.input_brushes = input_brushes;
self.report.emitted_convex_fragments = self.boxes.len();
for (bounds, material) in self.boxes {
mesh.append_box(bounds, material);
if let Some(reused_mesh) = reused_mesh {
self.report.reused_mesh = true;
mesh = reused_mesh;
} else {
for (bounds, material) in self.boxes {
mesh.append_box(bounds, material);
}
}
BuildOutput {
@ -722,9 +748,12 @@ impl BoxBuildState {
}
impl GeneralBuildState {
fn apply_compiled_brush(&mut self, brush: &CompiledBrush) {
fn apply_compiled_brush(&mut self, brush: &CompiledBrush) -> bool {
match brush.op {
BrushOp::Add => self.add_brush_geometry(brush),
BrushOp::Add => {
self.add_brush_geometry(brush);
true
}
BrushOp::Subtract => {
self.report.operator_brushes += 1;
if !brush
@ -732,7 +761,7 @@ impl GeneralBuildState {
.intersects_any(self.solids.iter().map(|solid| solid.bounds))
{
self.report.rejected_pairs += self.solids.len();
return;
return false;
}
if let Some(cutter) = brush.convex_cutter() {
self.solids = subtract_from_solids(
@ -740,6 +769,7 @@ impl GeneralBuildState {
&cutter,
&mut self.report,
);
true
} else {
let has_candidate =
record_solid_pairs(&self.solids, brush.bounds, &mut self.report);
@ -750,6 +780,7 @@ impl GeneralBuildState {
brush: brush.name.clone(),
});
}
false
}
}
BrushOp::Intersect => {
@ -758,9 +789,10 @@ impl GeneralBuildState {
.bounds
.intersects_any(self.solids.iter().map(|solid| solid.bounds))
{
let changed = !self.solids.is_empty();
self.report.rejected_pairs += self.solids.len();
self.solids.clear();
return;
return changed;
}
if let Some(cutter) = brush.convex_cutter() {
self.solids = intersect_solids(
@ -768,9 +800,11 @@ impl GeneralBuildState {
&cutter,
&mut self.report,
);
true
} else {
let has_candidate =
record_solid_pairs(&self.solids, brush.bounds, &mut self.report);
let changed = !self.solids.is_empty();
self.solids.clear();
if has_candidate {
self.report
@ -779,6 +813,7 @@ impl GeneralBuildState {
brush: brush.name.clone(),
});
}
changed
}
}
}
@ -845,11 +880,25 @@ impl GeneralBuildState {
}
}
fn into_output(mut self, input_brushes: usize, generation: u64) -> BuildOutput {
fn into_output(self, input_brushes: usize, generation: u64) -> BuildOutput {
self.into_output_with_mesh(input_brushes, generation, None)
}
fn into_output_with_mesh(
mut self,
input_brushes: usize,
generation: u64,
reused_mesh: Option<TriangleMesh>,
) -> BuildOutput {
self.report.input_brushes = input_brushes;
self.report.emitted_convex_fragments = self.solids.len();
for solid in self.solids {
solid.append_to_mesh(&mut self.mesh);
if let Some(reused_mesh) = reused_mesh {
self.report.reused_mesh = true;
self.mesh = reused_mesh;
} else {
for solid in self.solids {
solid.append_to_mesh(&mut self.mesh);
}
}
BuildOutput {
@ -1295,6 +1344,34 @@ mod tests {
);
}
#[test]
fn incremental_distant_tail_edit_reuses_previous_mesh() {
let mut asm = Assembler::new();
asm.solid_box(
"source",
Aabb::from_center_size(Vec3::ZERO, Vec3::splat(8.0)),
MaterialId(1),
);
let far = asm.cut_box(
"far",
Aabb::from_center_size(Vec3::splat(100.0), Vec3::splat(1.0)),
);
let before = asm.build_incremental();
assert!(asm.set_brush_primitive(
far,
Primitive::Box {
bounds: Aabb::from_center_size(Vec3::splat(120.0), Vec3::splat(1.0)),
},
));
let after = asm.build_incremental();
assert_eq!(after.mesh, before.mesh);
assert!(after.report.reused_mesh);
assert_eq!(after.report.candidate_pairs, 0);
assert_eq!(after.report.rejected_pairs, 1);
}
#[test]
fn incremental_convex_rebuild_matches_full_rebuild() {
let mut asm = Assembler::new();

4
src/convex.rs
View file

@ -29,7 +29,7 @@ impl Plane {
}
}
#[derive(Clone, Debug)]
#[derive(Clone, Debug, PartialEq)]
pub struct ConvexPolygon {
pub vertices: Vec<Vec3>,
pub normal: Vec3,
@ -73,7 +73,7 @@ impl ConvexPolygon {
}
}
#[derive(Clone, Debug)]
#[derive(Clone, Debug, PartialEq)]
pub struct ConvexSolid {
pub polygons: Vec<ConvexPolygon>,
pub clip_planes: Vec<Plane>,

2
src/mesh.rs
View file

@ -2,7 +2,7 @@ use bevy_math::{Vec2, Vec3};
use crate::{Aabb, MaterialId};
#[derive(Clone, Debug, Default)]
#[derive(Clone, Debug, Default, PartialEq)]
pub struct TriangleMesh {
pub positions: Vec<Vec3>,
pub normals: Vec<Vec3>,