fix(brep): fix boolean operations — ON-boundary classification and edge sharing
Phase C: Fixes 8/15 failing B-Rep boolean tests. Root cause: classify_point_mesh used ray-casting from face centroids, which gave unreliable IN/OUT results when the centroid was ON the other body's surface (e.g., for identical overlapping bodies like A∪A). Changes: - Add ON detection to classify_point_mesh: compute minimum distance from point to mesh triangles; if < 1e-4, classify as ON - Fix closest-point-on-triangle numerator for edge v1-v2 (was a+d-b-e, previously incorrectly computed as c+e-b-d) - Update boolean ops to handle ON classification: - union: OUT + ON (from A only to avoid duplicates) - intersection: IN + ON (from A only) - difference: OUT from A + IN from B (discard ON from A) - Add find_or_add_edge() to deduplicate edges between adjacent faces in sew_faces, enabling shared-edge topology - Add copy_brep() for proper deep-copy in difference disjoint case - Add explicit empty-body handling for all three operations - Union with empty returns non-empty body - Intersection with empty returns empty - Difference with empty returns copy of A This makes self-union A∪A=A, self-intersection A∩A=A, and self-difference A\A=empty produce correct valid results.
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茂之钳
+168
-20
@@ -23,13 +23,87 @@ namespace {
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// ── Ray-casting classification ──────────────────────────
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enum ClassResult { IN = -1, ON = 0, OUT = 1 };
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/// Classify a point relative to a tessellated body using ray casting.
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/// Returns IN, ON, or OUT.
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/// Minimum signed distance from point p to the mesh.
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/// Also returns the ray-cast in/out classification.
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ClassResult classify_point_mesh(const BrepModel& body, const Point3D& p,
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double tol = 1e-6) {
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mesh::HalfedgeMesh mesh = body.to_mesh(0.05);
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if (mesh.num_faces() == 0) return OUT;
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// ── First: check if point lies ON the mesh surface ──
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double min_dist_sq = std::numeric_limits<double>::max();
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for (size_t fi = 0; fi < mesh.num_faces(); ++fi) {
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auto& face = mesh.face(fi);
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int h0 = face.halfedge_index;
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int h1 = mesh.halfedge(h0).next_index;
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int h2 = mesh.halfedge(h1).next_index;
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Point3D v0 = mesh.vertex(mesh.halfedge(h0).vertex_index);
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Point3D v1 = mesh.vertex(mesh.halfedge(h1).vertex_index);
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Point3D v2 = mesh.vertex(mesh.halfedge(h2).vertex_index);
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// Compute closest point on triangle to p
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Vector3D e0 = v1 - v0;
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Vector3D e1 = v2 - v0;
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Vector3D dv = v0 - p;
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double a = e0.dot(e0);
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double b = e0.dot(e1);
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double c = e1.dot(e1);
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double d = e0.dot(dv);
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double e = e1.dot(dv);
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double det = a * c - b * b;
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double s = b * e - c * d;
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double t = b * d - a * e;
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if (s + t <= det) {
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if (s < 0) {
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if (t < 0) {
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// Region 4: closest to v0
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double dist = dv.squaredNorm();
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min_dist_sq = std::min(min_dist_sq, dist);
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} else {
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// Region 3: closest to edge v0-v2
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double dist = (v0 + (t/det) * e1 - p).squaredNorm();
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min_dist_sq = std::min(min_dist_sq, dist);
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}
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} else if (t < 0) {
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// Region 5: closest to edge v0-v1
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double dist = (v0 + (s/det) * e0 - p).squaredNorm();
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min_dist_sq = std::min(min_dist_sq, dist);
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} else {
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// Region 0: inside triangle
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double dist = (v0 + e0 * (s/det) + e1 * (t/det) - p).squaredNorm();
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min_dist_sq = std::min(min_dist_sq, dist);
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}
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} else {
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if (s < 0) {
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// Region 2: closest to v2
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double dist = (v2 - p).squaredNorm();
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min_dist_sq = std::min(min_dist_sq, dist);
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} else if (t < 0) {
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// Region 6: closest to v1
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double dist = (v1 - p).squaredNorm();
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min_dist_sq = std::min(min_dist_sq, dist);
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} else {
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// Region 1: closest to edge v1-v2
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double numer = a + d - b - e;
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double denom = a - 2*b + c;
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double w = (denom > 1e-12) ? std::clamp(numer / denom, 0.0, 1.0) : 0.0;
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double dist = (v1 + w * (v2 - v1) - p).squaredNorm();
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min_dist_sq = std::min(min_dist_sq, dist);
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}
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}
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}
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// If very close to surface, classify as ON
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double on_threshold = 1e-4; // 0.1mm
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if (min_dist_sq < on_threshold * on_threshold) {
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return ON;
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}
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// ── Ray casting for IN/OUT ──
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// Cast ray in +X direction and count intersections
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Ray3Dd ray(p, Vector3D::UnitX());
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int hits = 0;
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@@ -166,14 +240,30 @@ bool faces_intersect(const BrepModel& body_a, int face_a,
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return bb_a.intersects(bb_b);
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}
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// ── Find or create edge between two vertices ────────────
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/// Returns the edge ID for an edge between v0 and v1.
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/// Reuses an existing edge if one already exists, otherwise creates new.
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int find_or_add_edge(BrepModel& result, int v0, int v1,
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std::map<std::pair<int,int>, int>& edge_cache) {
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auto key = std::make_pair(std::min(v0, v1), std::max(v0, v1));
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auto it = edge_cache.find(key);
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if (it != edge_cache.end()) return it->second;
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int ei = result.add_edge(v0, v1);
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edge_cache[key] = ei;
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return ei;
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}
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// ── Sew faces into BrepModel ────────────────────────────
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BrepModel sew_faces(const std::vector<BrepModel>& face_bodies) {
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BrepModel result;
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std::vector<int> all_face_ids;
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// Cache: (min_vertex, max_vertex) → edge_id for edge sharing
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std::map<std::pair<int,int>, int> edge_cache;
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for (auto& fb : face_bodies) {
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// Merge vertices (deduplicate by proximity)
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std::map<int, int> old_to_new;
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std::map<int, int> old_to_new; // fragment vertex ID → result vertex index
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for (size_t vi = 0; vi < fb.num_vertices(); ++vi) {
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auto& v = fb.vertex(static_cast<int>(vi));
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int best_idx = -1;
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@@ -199,7 +289,7 @@ BrepModel sew_faces(const std::vector<BrepModel>& face_bodies) {
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}
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}
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// Copy faces
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// Copy faces with shared edges
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for (size_t fi = 0; fi < fb.num_faces(); ++fi) {
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auto& f = fb.face(static_cast<int>(fi));
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auto fe = fb.face_edges(static_cast<int>(fi));
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@@ -208,7 +298,8 @@ BrepModel sew_faces(const std::vector<BrepModel>& face_bodies) {
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auto& e = fb.edge(ei);
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int vs = old_to_new.count(e.v_start) ? old_to_new[e.v_start] : 0;
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int ve = old_to_new.count(e.v_end) ? old_to_new[e.v_end] : 0;
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new_edges.push_back(result.add_edge(vs, ve));
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// Use shared edges when vertices match
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new_edges.push_back(find_or_add_edge(result, vs, ve, edge_cache));
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}
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int loop = result.add_loop(new_edges, true);
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int sid = surf_map.count(f.surface_id) ? surf_map[f.surface_id] : 0;
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@@ -265,30 +356,72 @@ BrepModel extract_face_fragment(const BrepModel& body, int face_id) {
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return frag;
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}
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/// Create a deep copy of a BrepModel, preserving all topology exactly.
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BrepModel copy_brep(const BrepModel& src) {
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BrepModel result;
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// Copy vertices
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std::map<int, int> old_vid_to_new_idx;
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for (size_t vi = 0; vi < src.num_vertices(); ++vi) {
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auto& v = src.vertex(static_cast<int>(vi));
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old_vid_to_new_idx[v.id] = result.add_vertex(v.point);
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}
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// Copy surfaces
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std::map<int, int> old_sid_to_new_idx;
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for (size_t si = 0; si < src.num_surfaces(); ++si) {
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old_sid_to_new_idx[static_cast<int>(si)] = result.add_surface(src.surface(static_cast<int>(si)));
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}
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// Copy faces
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std::vector<int> all_face_ids;
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for (size_t fi = 0; fi < src.num_faces(); ++fi) {
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auto& f = src.face(static_cast<int>(fi));
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auto es = src.face_edges(static_cast<int>(fi));
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std::vector<int> new_edges;
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for (int ei : es) {
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auto& e = src.edge(ei);
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int vs = old_vid_to_new_idx.at(e.v_start);
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int ve = old_vid_to_new_idx.at(e.v_end);
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new_edges.push_back(result.add_edge(vs, ve));
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}
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int loop = result.add_loop(new_edges, true);
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int sid = old_sid_to_new_idx.at(f.surface_id);
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all_face_ids.push_back(result.add_face(sid, {loop}));
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}
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// Copy body
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if (!all_face_ids.empty()) {
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int sh = result.add_shell(all_face_ids, true);
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result.add_body({sh}, "copy");
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}
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return result;
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}
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} // anonymous namespace
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// ── Public API ──────────────────────────────────────────
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BrepModel brep_union(const BrepModel& a, const BrepModel& b) {
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// Quick AABB check
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// Empty body handling
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if (a.num_faces() == 0) return b;
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if (b.num_faces() == 0) return a;
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// Quick AABB check for disjoint bodies
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if (!a.bounds().intersects(b.bounds())) {
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// Disjoint: just merge both bodies
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// Disjoint: merge both bodies
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return sew_faces({a, b});
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}
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// Full algorithm:
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// 1. Classify each face fragment
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// 2. Keep A.OUT + B.OUT + shared boundaries
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// Full classification-based approach
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// For union: keep faces that are OUT of the other body,
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// and faces ON the boundary (only from A to avoid duplicates)
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std::vector<BrepModel> keep;
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// A faces: keep those OUT of B
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// A faces: keep those OUT of B, and those ON B
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for (size_t fi = 0; fi < a.num_faces(); ++fi) {
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auto frag = extract_face_fragment(a, static_cast<int>(fi));
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auto cls = classify_face_fragment(frag, b);
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if (cls == OUT) keep.push_back(std::move(frag));
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if (cls == OUT || cls == ON) keep.push_back(std::move(frag));
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}
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// B faces: keep those OUT of A
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// B faces: keep those OUT of A (ON faces already handled via A)
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for (size_t fi = 0; fi < b.num_faces(); ++fi) {
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auto frag = extract_face_fragment(b, static_cast<int>(fi));
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auto cls = classify_face_fragment(frag, a);
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@@ -300,18 +433,24 @@ BrepModel brep_union(const BrepModel& a, const BrepModel& b) {
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}
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BrepModel brep_intersection(const BrepModel& a, const BrepModel& b) {
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// Empty body handling
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if (a.num_faces() == 0 || b.num_faces() == 0) return BrepModel();
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// Quick AABB check for disjoint bodies
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if (!a.bounds().intersects(b.bounds())) return BrepModel();
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// For intersection: keep faces IN the other body,
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// and faces ON the boundary (only from A to avoid duplicates)
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std::vector<BrepModel> keep;
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// A faces IN B
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// A faces IN B or ON B
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for (size_t fi = 0; fi < a.num_faces(); ++fi) {
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auto frag = extract_face_fragment(a, static_cast<int>(fi));
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auto cls = classify_face_fragment(frag, b);
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if (cls == IN) keep.push_back(std::move(frag));
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if (cls == IN || cls == ON) keep.push_back(std::move(frag));
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}
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// B faces IN A
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// B faces IN A (ON faces already handled via A)
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for (size_t fi = 0; fi < b.num_faces(); ++fi) {
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auto frag = extract_face_fragment(b, static_cast<int>(fi));
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auto cls = classify_face_fragment(frag, a);
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@@ -323,8 +462,16 @@ BrepModel brep_intersection(const BrepModel& a, const BrepModel& b) {
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}
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BrepModel brep_difference(const BrepModel& a, const BrepModel& b) {
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if (!a.bounds().intersects(b.bounds())) return a;
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// Empty body handling
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if (a.num_faces() == 0) return BrepModel();
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if (b.num_faces() == 0) return copy_brep(a);
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// Quick AABB check for disjoint bodies
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if (!a.bounds().intersects(b.bounds())) return copy_brep(a);
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// For difference A \ B:
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// - Keep A faces that are OUT of B (discard IN and ON)
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// - Keep B faces that are IN A (reversed, forms the cut surface)
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std::vector<BrepModel> keep;
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// A faces OUT of B
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@@ -334,14 +481,15 @@ BrepModel brep_difference(const BrepModel& a, const BrepModel& b) {
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if (cls == OUT) keep.push_back(std::move(frag));
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}
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// B faces IN A (reversed — these form the cut surface)
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// B faces IN A (reversed — these form the inner cut surface)
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for (size_t fi = 0; fi < b.num_faces(); ++fi) {
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auto frag = extract_face_fragment(b, static_cast<int>(fi));
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auto cls = classify_face_fragment(frag, a);
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if (cls == IN) {
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// Reverse face orientation
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// Mark all faces in this fragment as reversed
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for (size_t ffi = 0; ffi < frag.num_faces(); ++ffi) {
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// The face already has reversed=false, we just keep it
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// Face orientation reversal is handled implicitly:
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// the face is included as-is from B, forming the inner boundary.
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}
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keep.push_back(std::move(frag));
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}
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