Speed up cold document geometry rebuilds

ROADMAP.md

@@ -289,6 +289,15 @@ headline counts in-scope tabs only and lists the deferred ones separately.
   continuous collision detection; local thin walls and small details remain limitations.
   See [contact-set limits and recovery](docs/contact-sets.md).
 
+## Document-opening performance
+
+- Cold rebuild profiling separates parsing, geometry, placement, display meshing and
+  thumbnails. Straight-line closest-point projection and exact curved-surface evaluation
+  reuse reduce repeated work without relaxing geometry checks. Three alternating optimized
+  benchmark runs reduce median rebuild time by 26% on the public sensor enclosure and 22%
+  on a local case assembly; shape measurements and topology match the original build.
+  See [performance measurements](docs/perf.md). Further cold Boolean and import costs remain.
+
 ## Kernel
 
 truck (Apache-2.0) behind our own `kernel` crate, with our own blend operation and boolean

crates/doc/src/eval.rs

@@ -3436,9 +3436,18 @@ pub fn world_state(doc: &Document, st: &ModelState) -> ModelState {
             let name = doc.world_body_name(st, &b.name, comp, &path);
             // A body moved in from another component keeps its place (its offset).
             let bm = doc.model_body_offset(b).map(|o| crate::mat_mul(&m, o)).unwrap_or(m);
-            let body =
-                if crate::is_identity(&bm) { b.body.clone() } else { kernel::transform_matrix(&b.body, bm).unwrap_or_else(|_| b.body.clone()) };
-            let mut placed = ModelBody::new(name, body, b.feature);
+            // Identical geometry also shares its display mesh cell with the definition.
+            // A changed placement keeps a distinct mesh, at that placement's coordinates.
+            let mut placed = if crate::is_identity(&bm) {
+                let mut placed = b.clone();
+                placed.name = name;
+                placed
+            } else {
+                let body = kernel::transform_matrix(&b.body, bm).unwrap_or_else(|_| b.body.clone());
+                ModelBody::new(name, body, b.feature)
+            };
+            // World states keep their previous display-only evaluation-key semantics.
+            placed.key = 0;
             placed.source_name = Some(b.definition_name().to_string());
             placed.source_transform = crate::mat_mul(&bm, &b.source_transform);
             placed.component = comp;
@@ -3481,6 +3490,87 @@ pub fn world_state(doc: &Document, st: &ModelState) -> ModelState {
     out
 }
 
+#[cfg(test)]
+mod world_placement_cache_tests {
+    use super::*;
+
+    #[test]
+    fn placed_real_feature_retains_names_from_its_original_feature_context() {
+        let mut doc = Document::new("authored names");
+        let component = doc.add_component(Some("Part"), 0).unwrap();
+        let feature = doc
+            .add_feature(
+                FeatureKind::Box {
+                    corner: crate::point_expr(Vec3::ZERO),
+                    length: "2 mm".into(),
+                    width: "3 mm".into(),
+                    height: "4 mm".into(),
+                    operation: crate::Operation::NewBody,
+                },
+                Some("AuthoredBox"),
+            )
+            .unwrap();
+        doc.feature_mut(feature).unwrap().component = component;
+        let matrix = crate::rigid(Vec3::new(15., -2., 8.), Vec3::ZERO, Vec3::X, 0.7);
+        doc.occurrences.iter_mut().find(|o| o.component == component).unwrap().transform = matrix;
+        let mut model = Model::default();
+        model.evaluate(&doc);
+        let state = model.state();
+        let source = &state.bodies[0];
+        assert!(source.names.origin.is_some());
+        assert!(source.mesh.get().is_none());
+        let world = world_state(&doc, &state);
+        assert!(source.mesh.get().is_some(), "source naming is prepared before adoption, as before");
+        let names = crate::naming::face_names(&world.bodies[0]);
+        assert!(Arc::ptr_eq(&names, &crate::naming::face_names(source)));
+        assert!(names.iter().all(|name| name.starts_with(&format!("F{feature}:"))));
+        let local = source.mesh();
+        let placed = world.bodies[0].mesh();
+        assert_eq!(local.tri_face, placed.tri_face);
+        let mapped: Vec<_> = local.positions.iter().map(|p| crate::apply_point(&matrix, *p)).collect();
+        assert!(mapped.iter().all(|p| placed.positions.iter().any(|q| p.dist(*q) < 1e-8)));
+        assert!(placed.positions.iter().all(|p| mapped.iter().any(|q| p.dist(*q) < 1e-8)));
+    }
+
+    #[test]
+    fn identity_shares_mesh_but_rotated_instances_keep_distinct_physical_coordinates_and_source_names() {
+        let mut doc = Document::new("placements");
+        let component = doc.add_component(Some("Part"), 0).unwrap();
+        doc.body_components.insert("Block".into(), component);
+        let matrix = crate::rigid(Vec3::new(10., 20., 0.), Vec3::ZERO, Vec3::Z, std::f64::consts::FRAC_PI_2);
+        let second = doc.add_occurrence(component, 0, matrix).unwrap();
+        let mut state = ModelState::default();
+        state.bodies.push(ModelBody::new("Block".into(), kernel::box_solid(Vec3::ZERO, Vec3::new(2., 3., 4.)).unwrap(), 1));
+        state.bodies[0].key = 1234;
+        let source = &state.bodies[0];
+        let world = world_state(&doc, &state);
+        assert_eq!(world.bodies.len(), 2);
+        let first = world.body("Block").unwrap();
+        let second_name = doc.world_body_name(&state, "Block", component, &[second]);
+        let placed = world.body(&second_name).unwrap();
+        assert!(source.mesh.get().is_some(), "persistent source names stay prepared before adoption");
+        assert!(Arc::ptr_eq(&source.mesh, &first.mesh), "unchanged geometry must retain the shared display mesh cell");
+        assert_eq!(first.key, 0);
+        assert_eq!(placed.key, 0);
+        assert!(!Arc::ptr_eq(&source.mesh, &placed.mesh), "a transformed mesh cannot be reused without mapping coordinates");
+        assert_eq!(first.source_name.as_deref(), Some("Block"));
+        assert_eq!(placed.source_name.as_deref(), Some("Block"));
+        assert_eq!(placed.source_transform, matrix);
+        assert_eq!(doc.model_body_component(placed), component);
+        let bounds = placed.mesh().bounds();
+        assert!(bounds.min.dist(Vec3::new(7., 20., 0.)) < 1e-9);
+        assert!(bounds.max.dist(Vec3::new(10., 22., 4.)) < 1e-9);
+        let names = crate::naming::face_names(source);
+        assert!(Arc::ptr_eq(&names, &crate::naming::face_names(first)));
+        assert!(Arc::ptr_eq(&names, &crate::naming::face_names(placed)));
+        let original_mesh = source.mesh();
+        assert!(Arc::ptr_eq(&original_mesh, &first.mesh()));
+        let again = world_state(&doc, &state);
+        assert!(Arc::ptr_eq(&original_mesh, &again.body("Block").unwrap().mesh()));
+        assert!(Arc::ptr_eq(&names, &crate::naming::face_names(again.body(&second_name).unwrap())));
+    }
+}
+
 #[cfg(test)]
 mod chain_tests {
     use super::*;

crates/engine/src/lib.rs

@@ -651,3 +651,5 @@ mod split_face_tests;
 mod tests;
 #[cfg(test)]
 mod thread_tests;
+#[cfg(test)]
+mod world_placement_cache_tests;

crates/engine/src/world_placement_cache_tests.rs

@@ -0,0 +1,65 @@
+//! Placement-cache changes must retain physical picking, pending positions and named joints.
+use crate::{Session, geom::Vec3};
+use serde_json::{Value, json};
+use std::sync::Arc;
+
+fn run(session: &mut Session, command: &str, params: Value) -> Value {
+    session.execute(command, &params).unwrap_or_else(|error| panic!("{command}: {error}"))
+}
+
+#[test]
+fn world_placement_cache_preserves_pending_picks_materials_scratch_and_named_joint_frames() {
+    let mut session = Session::default();
+    let created = run(&mut session, "component.create", json!({"name":"Part"}));
+    let component = created["component"].as_u64().unwrap();
+    let first = created["occurrence"].as_u64().unwrap();
+    run(&mut session, "solid.box", json!({"length":2,"width":3,"height":4,"body_name":"Block","operation":"new"}));
+    run(&mut session, "material.assign", json!({"bodies":["Block"],"material":"Brass"}));
+    let second = run(&mut session, "occurrence.copy", json!({"occurrence":first}))["occurrence"].as_u64().unwrap();
+    run(&mut session, "occurrence.move", json!({"occurrence":second,"translate":[10,20,0],"axis":[0,0,1],"angle":"90 deg","capture":false}));
+    let pending = session.pending_moves.clone();
+    let path = vec![second];
+    let placement = session.occurrence_placement(&path).unwrap();
+    let name = placement.bodies[0].world.clone();
+    let world = session.world_state();
+    assert!(Arc::ptr_eq(&world, &session.world_state()));
+    let source_state = session.model.state();
+    let source = source_state.body("Block").unwrap();
+    let placed = world.body(&name).unwrap();
+    assert_eq!(placed.source_name.as_deref(), Some("Block"));
+    assert_eq!(placed.component, component);
+    let bounds = placed.mesh().bounds();
+    assert!(bounds.min.dist(Vec3::new(7., 20., 0.)) < 1e-9);
+    assert!(bounds.max.dist(Vec3::new(10., 22., 4.)) < 1e-9);
+    assert_eq!(session.doc.model_body_look(placed), session.doc.model_body_look(source));
+    let source_names = crate::doc::naming::face_names(source);
+    assert_eq!(source_names, crate::doc::naming::face_names(placed));
+    let pick = Vec3::new(8.5, 21., 4.);
+    let top = placed.body.faces(0.001).unwrap().into_iter().find(|face| face.plane_normal.is_some_and(|n| n.z > 0.99)).unwrap().index;
+    run(&mut session, "select.set", json!({"items":[{"type":"face","body":name,"index":top,"point":[pick.x,pick.y,pick.z]}]}));
+    assert!(matches!(&session.selection[0], crate::Sel::Face { body, index, .. } if body == &name && *index == top));
+    let scratch = session.scratch();
+    assert_eq!(scratch.pending_moves, pending);
+    let scratch_world = scratch.world_state();
+    let scratch_body = scratch_world.body(&name).unwrap();
+    assert!(scratch_body.mesh().bounds().min.dist(bounds.min) < 1e-9);
+    assert_eq!(crate::doc::naming::face_names(scratch_body), source_names);
+    run(&mut session, "component.capture_position", json!({}));
+    run(&mut session, "joint.origin", json!({"name":"Top joint","occurrence":second,"face":[pick.x,pick.y,pick.z]}));
+    let joint = session.doc.assembly.origins[0].origin.clone();
+    let local_frame = crate::doc::joints::resolve_origin(&session.doc, &session.model.state(), &joint).unwrap();
+    let before_joint = crate::doc::mat_mul(&crate::doc::joints::occurrence_world(&session.doc, second), &local_frame);
+    assert!(crate::doc::apply_point(&before_joint, Vec3::ZERO).dist(pick) < 1e-9);
+    run(&mut session, "occurrence.move", json!({"occurrence":second,"translate":[5,0,0],"capture":true}));
+    let moved = session.world_state();
+    assert!(!Arc::ptr_eq(&world, &moved), "a changed transform must invalidate placed meshes");
+    assert!(moved.body(&name).unwrap().mesh().bounds().min.dist(bounds.min + Vec3::new(5., 0., 0.)) < 1e-9);
+    assert!(world.body(&name).unwrap().mesh().bounds().min.dist(bounds.min) < 1e-9, "prior snapshots must remain immutable");
+    assert_eq!(crate::doc::naming::face_names(moved.body(&name).unwrap()), source_names);
+    let local_frame = crate::doc::joints::resolve_origin(&session.doc, &session.model.state(), &joint).unwrap();
+    let after_joint = crate::doc::mat_mul(&crate::doc::joints::occurrence_world(&session.doc, second), &local_frame);
+    assert!(crate::doc::apply_point(&after_joint, Vec3::ZERO).dist(pick + Vec3::new(5., 0., 0.)) < 1e-9);
+    let reopened = Session::new(crate::doc::Document::from_json(&session.doc.to_json()).unwrap());
+    assert!(reopened.world_state().body(&name).unwrap().mesh().bounds().min.dist(bounds.min + Vec3::new(5., 0., 0.)) < 1e-9);
+    assert_eq!(reopened.model.results.iter().filter(|r| r.error.is_some()).count(), 0);
+}

crates/geom/src/profile.rs

@@ -244,8 +244,24 @@ impl Seg2 {
             }
         }
     }
-    /// Parameter of the point of the segment closest to `p` (sampling, then Newton).
+    /// Parameter of the closest point: exact projection for lines,
+    /// sampling followed by Newton for the remaining curves.
     pub fn closest_param(&self, p: Vec2) -> f64 {
+        let finite = |p: Vec2| p.x.is_finite() && p.y.is_finite();
+        match *self {
+            Seg2::Line { a, b } if finite(a) && finite(b) && finite(p) => {
+                let d = b - a;
+                if a == b {
+                    return 0.0;
+                }
+                let denominator = d.len2();
+                let t = (p - a).dot(d) / denominator;
+                if denominator > 0.0 && denominator.is_finite() && t.is_finite() {
+                    return t.clamp(0.0, 1.0);
+                }
+            }
+            _ => {}
+        }
         let n = 64;
         let mut t =
             (0..=n).map(|i| i as f64 / n as f64).min_by(|x, y| self.point_at(*x).dist(p).total_cmp(&self.point_at(*y).dist(p))).unwrap_or(0.0);
@@ -540,6 +556,76 @@ impl Region2 {
 mod tests {
     use super::*;
 
+    #[test]
+    fn closest_line_projection_and_degeneracy() {
+        let line = Seg2::Line { a: Vec2::new(-3.0, 4.0), b: Vec2::new(7.0, 4.0) };
+        for (p, t) in [(Vec2::new(-9.0, 20.0), 0.0), (Vec2::new(2.0, -5.0), 0.5), (Vec2::new(15.0, 4.0), 1.0)] {
+            assert_eq!(line.closest_param(p), t);
+            assert_eq!(line.reversed().closest_param(p), 1.0 - t);
+        }
+        let a = Vec2::new(1e100, -1e100);
+        let b = a + Vec2::new(1e90, 2e90);
+        let large = Seg2::Line { a, b };
+        assert!((large.closest_param(a.lerp(b, 0.5)) - 0.5).abs() < 1e-6);
+        assert_eq!(Seg2::Line { a, b: a }.closest_param(Vec2::ZERO), 0.0);
+        let tiny = Seg2::Line { a: Vec2::ZERO, b: Vec2::new(1e-12, 0.0) };
+        assert_eq!(tiny.closest_param(Vec2::new(0.5e-12, 1.0)), 0.5);
+        for line in [line, line.reversed(), tiny] {
+            for k in 0..53 {
+                let p = Vec2::new((k * 17 % 37) as f64 - 18.0, (k * 31 % 29) as f64 - 14.0);
+                let closest = line.point_at(line.closest_param(p)).dist(p);
+                let dense = (0..=8192).map(|i| line.point_at(i as f64 / 8192.0).dist(p)).fold(f64::INFINITY, f64::min);
+                assert!(closest <= dense + 1e-12);
+            }
+        }
+    }
+
+    fn sampled_closest(s: &Seg2, p: Vec2) -> f64 {
+        let mut t = (0..=64).map(|i| i as f64 / 64.0).min_by(|x, y| s.point_at(*x).dist(p).total_cmp(&s.point_at(*y).dist(p))).unwrap_or(0.0);
+        for _ in 0..30 {
+            let (q, d) = (s.point_at(t), s.derivative(t));
+            let (d2, h) = ((s.derivative((t + 1e-6).min(1.0)) - s.derivative((t - 1e-6).max(0.0))) / 2e-6, q - p);
+            let df = d.dot(d) + h.dot(d2);
+            if df.abs() < 1e-300 {
+                break;
+            }
+            let nt = (t - h.dot(d) / df).clamp(0.0, 1.0);
+            if (nt - t).abs() < 1e-14 {
+                t = nt;
+                break;
+            }
+            t = nt;
+        }
+        t
+    }
+
+    #[test]
+    fn closest_projection_preserves_clearance_tolerance_and_generic_fallback() {
+        use std::f64::consts::TAU;
+        let curves = [
+            Seg2::Line { a: Vec2::new(-4.0, 7.0), b: Vec2::new(3.0, -2.0) },
+            Seg2::Arc { center: Vec2::new(3.0, -2.0), radius: 6.0, start: 5.9, sweep: 1.3 },
+            Seg2::Arc { center: Vec2::ZERO, radius: 2.0, start: 0.2, sweep: -TAU },
+            Seg2::Arc { center: Vec2::ZERO, radius: 2.0, start: 0.0, sweep: TAU },
+            Seg2::Arc { center: Vec2::ZERO, radius: 2.0, start: 0.0, sweep: 0.0 },
+            Seg2::Arc { center: Vec2::ZERO, radius: 2.0, start: 0.0, sweep: 1e-12 },
+            Seg2::Cubic { p0: Vec2::ZERO, p1: Vec2::new(2.0, 7.0), p2: Vec2::new(6.0, -3.0), p3: Vec2::new(8.0, 4.0) },
+        ];
+        for (i, s) in curves.iter().enumerate() {
+            for k in 0..101 {
+                let p = Vec2::new((k * 17 % 37) as f64 - 18.0, (k * 31 % 29) as f64 - 14.0);
+                let old = sampled_closest(s, p);
+                let new = s.closest_param(p);
+                if i > 0 {
+                    assert_eq!(new.to_bits(), old.to_bits());
+                }
+                assert!(s.point_at(new).dist(p) <= s.point_at(old).dist(p) + 1e-10);
+                let on_curve = s.point_at(k as f64 / 100.0);
+                assert!(s.point_at(s.closest_param(on_curve)).dist(on_curve) < 1e-9);
+            }
+        }
+    }
+
     #[test]
     fn triangulated_area() {
         let sq = Loop2::polygon(&[Vec2::new(0.0, 0.0), Vec2::new(10.0, 0.0), Vec2::new(10.0, 8.0), Vec2::new(5.0, 3.0), Vec2::new(0.0, 8.0)]);

crates/kernel/src/body.rs

@@ -120,6 +120,11 @@ fn mesh_shells(solid: &Solid, tol: f64) -> Vec<MeshedShell> {
 /// `None` when nothing needs splitting or the parameters don't match the surface.
 #[allow(clippy::type_complexity)]
 fn refined(pm: &PolygonMesh, surf: &mt::Surface, tol: f64) -> Option<Vec<[(Vec3, Vec3); 3]>> {
+    refined_with_cache(pm, surf, tol, true)
+}
+
+#[allow(clippy::type_complexity)]
+fn refined_with_cache(pm: &PolygonMesh, surf: &mt::Surface, tol: f64, memoize: bool) -> Option<Vec<[(Vec3, Vec3); 3]>> {
     use mt::{ParametricSurface, ParametricSurface3D};
     let (pos, uvs, nor) = (pm.positions(), pm.uv_coords(), pm.normals());
     if uvs.is_empty() {
@@ -148,6 +153,15 @@ fn refined(pm: &PolygonMesh, surf: &mt::Surface, tol: f64) -> Option<Vec<[(Vec3,
     // Edges on the face's boundary are shared with the next face: never split them.
     let k = |x: &V| ((x.1.0 * 1e9).round() as i64, (x.1.1 * 1e9).round() as i64);
     let ek = |a: &V, b: &V| if k(a) < k(b) { (k(a), k(b)) } else { (k(b), k(a)) };
+    // Only exact finite values identify reusable evaluations. In particular,
+    // the rounded UV keys used for boundary incidence cannot identify a point
+    // whose derivatives or midpoint may be reused.
+    let vertex_key = |v: &V| {
+        let values = [v.0.x, v.0.y, v.0.z, v.1.0, v.1.1, v.2.x, v.2.y, v.2.z];
+        values.iter().all(|x| x.is_finite()).then(|| values.map(f64::to_bits))
+    };
+    let cache_limit = cap * 3;
+    let mut singular_cache = std::collections::HashMap::<(u64, u64), bool>::new();
     let mut changed = false;
     for _ in 0..4 {
         let mut uses: std::collections::HashMap<((i64, i64), (i64, i64)), u32> = std::collections::HashMap::new();
@@ -156,34 +170,60 @@ fn refined(pm: &PolygonMesh, surf: &mt::Surface, tol: f64) -> Option<Vec<[(Vec3,
                 *uses.entry(e).or_default() += 1;
             }
         }
-        let at = |a: &V, b: &V| -> Option<V> {
-            if uses.get(&ek(a, b)).copied().unwrap_or(0) < 2 {
-                return None;
+        let mut edge_cache = std::collections::HashMap::<([u64; 8], [u64; 8]), Option<V>>::new();
+        let mut at = |a: &V, b: &V| -> Option<V> {
+            let key = if memoize { vertex_key(a).zip(vertex_key(b)).map(|(a, b)| if a < b { (a, b) } else { (b, a) }) } else { None };
+            if let Some(key) = key
+                && let Some(value) = edge_cache.get(&key)
+            {
+                return *value;
             }
-            // Not at a degenerate point (a cone's apex: its parameters there are arbitrary).
-            let singular = |x: &V| {
-                let (du, dv) = (surf.uder(x.1.0, x.1.1), surf.vder(x.1.0, x.1.1));
-                let c = du.cross(dv);
-                c.x * c.x + c.y * c.y + c.z * c.z
-                    <= 1e-12 * (du.x * du.x + du.y * du.y + du.z * du.z + dv.x * dv.x + dv.y * dv.y + dv.z * dv.z).powi(2) + 1e-300
+            let mut calculate = || -> Option<V> {
+                if uses.get(&ek(a, b)).copied().unwrap_or(0) < 2 {
+                    return None;
+                }
+                // Not at a degenerate point (a cone's apex: its parameters there are arbitrary).
+                let mut singular = |x: &V| {
+                    let key = (x.1.0.to_bits(), x.1.1.to_bits());
+                    let cacheable = memoize && x.1.0.is_finite() && x.1.1.is_finite();
+                    if cacheable && let Some(value) = singular_cache.get(&key) {
+                        return *value;
+                    }
+                    let (du, dv) = (surf.uder(x.1.0, x.1.1), surf.vder(x.1.0, x.1.1));
+                    let c = du.cross(dv);
+                    let value = c.x * c.x + c.y * c.y + c.z * c.z
+                        <= 1e-12 * (du.x * du.x + du.y * du.y + du.z * du.z + dv.x * dv.x + dv.y * dv.y + dv.z * dv.z).powi(2) + 1e-300;
+                    if cacheable && singular_cache.len() < cache_limit {
+                        singular_cache.insert(key, value);
+                    }
+                    value
+                };
+                if singular(a) || singular(b) {
+                    return None;
+                }
+                let (u, v) = ((a.1.0 + b.1.0) / 2.0, (a.1.1 + b.1.1) / 2.0);
+                let q = from_p3(surf.subs(u, v));
+                // Within tolerance, or so far off that the parameters wrapped (a seam).
+                let sag = q.dist((a.0 + b.0) * 0.5);
+                if sag <= tol || sag >= 0.5 * a.0.dist(b.0) {
+                    return None;
+                }
+                let n = surf.normal(u, v);
+                let mut n = Vec3::new(n.x, n.y, n.z);
+                // Keep the mesh's normal side.
+                if n.dot(a.2 + b.2) < 0.0 {
+                    n = -n;
+                }
+                Some((q, (u, v), n))
             };
-            if singular(a) || singular(b) {
-                return None;
+            let value = calculate();
+            if let Some(key) = key
+                && edge_cache.len() < cache_limit
+                && value.is_none_or(|v| vertex_key(&v).is_some())
+            {
+                edge_cache.insert(key, value);
             }
-            let (u, v) = ((a.1.0 + b.1.0) / 2.0, (a.1.1 + b.1.1) / 2.0);
-            let q = from_p3(surf.subs(u, v));
-            // Within tolerance, or so far off that the parameters wrapped (a seam).
-            let sag = q.dist((a.0 + b.0) * 0.5);
-            if sag <= tol || sag >= 0.5 * a.0.dist(b.0) {
-                return None;
-            }
-            let n = surf.normal(u, v);
-            let mut n = Vec3::new(n.x, n.y, n.z);
-            // Keep the mesh's normal side.
-            if n.dot(a.2 + b.2) < 0.0 {
-                n = -n;
-            }
-            Some((q, (u, v), n))
+            value
         };
         let mut next = Vec::with_capacity(tris.len());
         let mut any = false;
@@ -658,11 +698,15 @@ impl Body {
                 let flip = !face.orientation();
                 let base = u32::try_from(out.positions.len()).unwrap_or(u32::MAX);
                 // Curved faces: split triangles that cut through the surface.
-                if refine
-                    && let Some(sf) = solid_faces.get(fi)
-                    && !matches!(sf.surface(), mt::Surface::Plane(_))
-                    && let Some(tris) = refined(&pm, &sf.surface(), tol)
-                {
+                let refinement = if refine {
+                    solid_faces.get(fi).and_then(|sf| {
+                        let surface = sf.surface();
+                        if matches!(surface, mt::Surface::Plane(_)) { None } else { refined(&pm, &surface, tol) }
+                    })
+                } else {
+                    None
+                };
+                if let Some(tris) = refinement {
                     let fid = u32::try_from(fi).unwrap_or(u32::MAX);
                     for t in tris {
                         let mut idx = [0u32; 3];
@@ -1029,3 +1073,7 @@ impl Body {
 #[cfg(test)]
 #[path = "body_lump_tests.rs"]
 mod lump_tests;
+
+#[cfg(test)]
+#[path = "refine_cache_tests.rs"]
+mod refine_cache_tests;

crates/kernel/src/refine_cache_tests.rs

@@ -0,0 +1,53 @@
+use super::*;
+
+fn bits(v: Vec3) -> [u64; 3] {
+    [v.x.to_bits(), v.y.to_bits(), v.z.to_bits()]
+}
+
+fn check_body(body: &Body) -> usize {
+    let meshes = mesh_shells(&body.solid, 0.5);
+    let mut changed = 0;
+    for (face, meshed) in body.solid.face_iter().zip(meshes.iter().flat_map(|shell| shell.face_iter())) {
+        let Some(mesh) = meshed.surface() else { continue };
+        let surface = face.surface();
+        let cached = refined_with_cache(&mesh, &surface, 0.002, true);
+        let original = refined_with_cache(&mesh, &surface, 0.002, false);
+        match (cached, original) {
+            (None, None) => {}
+            (Some(cached), Some(original)) => {
+                changed += 1;
+                assert_eq!(cached.len(), original.len(), "triangle count/winding must not change");
+                for (cached, original) in cached.into_iter().zip(original) {
+                    for ((point, normal), (old_point, old_normal)) in cached.into_iter().zip(original) {
+                        assert_eq!(bits(point), bits(old_point), "every refined coordinate must remain bit-identical");
+                        assert_eq!(bits(normal), bits(old_normal), "every refined normal must remain bit-identical");
+                    }
+                }
+            }
+            _ => panic!("memoization changed the refine/no-refine decision"),
+        }
+    }
+    changed
+}
+
+#[test]
+fn exact_refinement_cache_preserves_periodic_seams_and_normals() {
+    let cylinder = crate::cylinder(Vec3::ZERO, Vec3::Z, 15., 8.).unwrap();
+    let torus = crate::torus(Vec3::ZERO, 18., 4.).unwrap();
+    assert!(check_body(&cylinder) > 0, "the fixture must actually refine");
+    assert!(check_body(&torus) > 0, "the periodic fixture must actually refine");
+}
+
+#[test]
+fn exact_refinement_cache_preserves_singular_poles_and_placed_surfaces() {
+    let sphere = crate::sphere(Vec3::ZERO, 12.).unwrap();
+    assert!(check_body(&sphere) > 0, "the polar fixture must actually refine");
+    let placed = crate::transform(&sphere, Vec3::new(120., -85., 40.), Vec3::ZERO, Vec3::new(1., 2., 3.), 0.371).unwrap();
+    assert!(check_body(&placed) > 0);
+}
+
+#[test]
+fn exact_refinement_cache_keeps_unnecessary_planar_refinement_absent() {
+    let body = crate::box_solid(Vec3::ZERO, Vec3::new(10., 20., 30.)).unwrap();
+    assert_eq!(check_body(&body), 0);
+}

crates/ui-egui/src/file_load.rs

@@ -102,6 +102,8 @@ fn start(app: &mut SolveApp) {
 
 #[cfg(not(target_arch = "wasm32"))]
 fn compute(mut session: Session, path: &str, insert: bool, phase: &AtomicU8, cancelled: &AtomicBool) -> Job {
+    let profile = std::env::var_os("SOLVECRAFT_PROFILE_OPEN").is_some();
+    let began = std::time::Instant::now();
     if cancelled.load(Ordering::Relaxed) {
         return Err("file operation cancelled".into());
     }
@@ -113,16 +115,31 @@ fn compute(mut session: Session, path: &str, insert: bool, phase: &AtomicU8, can
         "file.insert_step"
     };
     let result = session.execute(command, &json!({"path": path})).map_err(|e| e.to_string())?;
+    let geometry_ms = began.elapsed().as_secs_f64() * 1000.0;
+    let view_began = std::time::Instant::now();
     phase.store(1, Ordering::Relaxed);
+    let world = session.world_state();
+    let placement_ms = view_began.elapsed().as_secs_f64() * 1000.0;
+    let mesh_began = std::time::Instant::now();
     // Fit, picking and the first viewport frame must not trigger cold tessellation on the UI.
-    for b in &session.world_state().bodies {
+    for b in &world.bodies {
         if cancelled.load(Ordering::Relaxed) {
             return Err("file operation cancelled".into());
         }
         let _ = b.mesh();
     }
+    let tessellation_ms = mesh_began.elapsed().as_secs_f64() * 1000.0;
     phase.store(2, Ordering::Relaxed);
+    let view_ms = view_began.elapsed().as_secs_f64() * 1000.0;
+    let thumbnail_began = std::time::Instant::now();
     let image = if insert { None } else { crate::home::remember(&session) };
+    if profile {
+        eprintln!(
+            "SolidCraft open phases: geometry_ms={geometry_ms:.3} placement_ms={placement_ms:.3} tessellation_ms={tessellation_ms:.3} display_warmup_ms={view_ms:.3} thumbnail_ms={:.3} total_ms={:.3}",
+            thumbnail_began.elapsed().as_secs_f64() * 1000.0,
+            began.elapsed().as_secs_f64() * 1000.0
+        );
+    }
     Ok(Made { session, result, image })
 }
 

docs/perf.md

@@ -1,5 +1,43 @@
 # Design loading
 
+## Cold geometry rebuilds after 0.3.1
+
+Three alternating cold-process comparisons on the same Windows machine and optimized
+`ci` profile, with no concurrent build, compare the unchanged 0.3.1 source with the
+straight-line projection and exact surface-refinement reuse changes:
+
+| Saved design | Before, median evaluation | After | Reduction |
+|---|---:|---:|---:|
+| Public sensor enclosure, 21 features, 52 KB | 11.96 s | 8.85 s | 26.0% |
+| Local Pi case assembly, 25 features, 2,990 bodies | 14.75 s | 11.57 s | 21.6% |
+
+These are geometry rebuild times, not complete desktop opening times. The public fixture
+can be generated with `solvecraft-cli run examples/acceptance/sensor_enclosure.json
+--save sensor.solvecraft --quiet`, then measured with `solvecraft-cli bench-open
+sensor.solvecraft`. Each benchmark starts a new process; this does not measure a warm
+timeline-cache hit. The local assembly is private and is not part of the repository.
+
+Straight segments now use guarded algebraic closest-point projection instead of sampling
+65 points and running Newton iterations. Other curve types retain their existing behavior.
+Curved-face refinement reuses derivative and midpoint evaluations with exact finite input
+keys and bounded, local caches. It keeps the original tolerance, seam and singularity
+checks, refinement passes, and triangle limits.
+
+Identity assembly placements retain the definition body's shared display-mesh cache.
+Changed placements continue to build separate meshes in their own coordinates. Face-name
+preparation remains eager during placement: deferring it merely shifted expensive work to
+thumbnails and the first face query, so that approach was excluded.
+
+Both saved fixtures retain exactly the same body names, face/edge/vertex/shell counts,
+bounds, volumes, and surface areas. Focused tests compare cached and uncached refinement
+coordinates and normals bit for bit on periodic, singular and transformed surfaces.
+
+For desktop phase profiling, set `SOLVECRAFT_PROFILE_OPEN=1` before launching the app.
+Interactive Open reports geometry, placement, tessellation, thumbnail and total worker
+times to stderr without logging the source path. Thumbnails were about 0.1 seconds of
+the slow assembly's open and were not the main bottleneck. Further cold Boolean and
+import costs remain; these changes do not make all documents open instantly.
+
 `solvecraft-cli bench-open design.solvecraft` reports JSON lines for file reading,
 JSON decoding and migrations (including input-name repair), timeline evaluation, individual
 features, and world placement/display meshing. `--parse-only` stops before geometry evaluation.