M4: delete-face direct edit — remove faces and heal via OCCT defeaturing

New CadFeatureType::DeleteFace: removes a set of global face ids from target_body
and heals the gap via BRepAlgoAPI_Defeaturing (TKBO, already linked), mirroring the
Shell/Draft body-modifying pattern. delete_faces appended to both symmetric cereal
lists (recipe version stays 2, golden fixture regenerated 27913->28161). MCP
delete_face method (pure additions). 3 new [CadDocument][deleteface] tests: remove a
fillet face restores the sharp-box volume, bad index fails safely, round-trip.
Full kernel suite green (79 cases, 1309 asserts).

Move-face / replace-face deferred to snaporca-3c4 / snaporca-tc6 (no clean shipping
OCCT direct-modeling primitive; need research, and replace-face depends on M7 surfaces).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BVzKmX6Y1aEteit1HTXG4Q

src/libslic3r/CadDocument.cpp

@@ -13,6 +13,7 @@
 #include <BRepAlgoAPI_Fuse.hxx>
 #include <BRepAlgoAPI_Cut.hxx>
 #include <BRepAlgoAPI_Common.hxx>
+#include <BRepAlgoAPI_Defeaturing.hxx>
 #include <BRepAlgoAPI_BooleanOperation.hxx>
 #include <BRepOffsetAPI_MakePipe.hxx>
 #include <BRepOffsetAPI_MakePipeShell.hxx>
@@ -680,6 +681,18 @@ int CadDocument::add_shell(double thickness, int face, int target_body, const st
     return int(features.size()) - 1;
 }
 
+int CadDocument::add_delete_face(int target_body, const std::vector<int>& faces,
+                                  const std::string& name)
+{
+    CadFeature f;
+    f.type         = CadFeatureType::DeleteFace;
+    f.name         = name;
+    f.target_body  = target_body;
+    f.delete_faces = faces;
+    features.push_back(f);
+    return int(features.size()) - 1;
+}
+
 int CadDocument::add_draft(double angle, int face, int target_body, const std::string& name)
 {
     CadFeature f;
@@ -1873,6 +1886,22 @@ void CadDocument::apply_feature(TopoDS_Shape& result, bool& have_body,
         if (result.IsNull()) throw std::runtime_error("draft produced no geometry");
         break;
     }
+    case CadFeatureType::DeleteFace: {
+        if (!have_body) throw std::runtime_error("delete_face needs a body");
+        if (f.delete_faces.empty()) throw std::runtime_error("delete_face needs at least one face");
+        BRepAlgoAPI_Defeaturing df;
+        df.SetShape(result);
+        for (int fi : f.delete_faces) {
+            TopoDS_Face fc = GeometryEngine::face_by_index(result, fi);
+            if (fc.IsNull()) throw std::runtime_error("delete_face: face not found");
+            df.AddFaceToRemove(fc);
+        }
+        df.Build();
+        if (!df.IsDone()) throw std::runtime_error("delete_face failed");
+        result = df.Shape();
+        if (result.IsNull()) throw std::runtime_error("delete_face produced no geometry");
+        break;
+    }
     }
 }
 

src/libslic3r/CadDocument.hpp

@@ -17,7 +17,7 @@
 
 namespace Slic3r {
 
-enum class CadFeatureType { Sketch, Extrude, Fillet, Chamfer, Hole, Thread, Shell, Revolve, Sweep, Pattern, Plane, Loft, Draft, Import, Boolean, Cut, Mirror, Axis, CoordSys, Helix, Transform, Thicken, Project };
+enum class CadFeatureType { Sketch, Extrude, Fillet, Chamfer, Hole, Thread, Shell, Revolve, Sweep, Pattern, Plane, Loft, Draft, Import, Boolean, Cut, Mirror, Axis, CoordSys, Helix, Transform, Thicken, Project, DeleteFace };
 enum class SketchShape    { Rectangle, Circle };
 enum class PlaneType      { Offset, Angle, Midplane, Tangent, TwoEdges, Coincident };
 enum class AxisType       { TwoPoints, FaceNormal, CylinderCenterline, PlaneIntersection, AlongEdge };
@@ -263,6 +263,10 @@ struct CadFeature {
     std::vector<int> project_edges;             // global edge ids to project; empty => use project_face
     int              project_face{-1};          // if project_edges empty, project every edge of this face
 
+    // Direct edit: faces to remove (global face indices into target_body's shape),
+    // healed via BRepAlgoAPI_Defeaturing.
+    std::vector<int> delete_faces;
+
     template<class Archive>
     void save(Archive& ar) const {
         std::string brep = (type == CadFeatureType::Import) ? brep_to_string(imported_solid) : std::string();
@@ -292,7 +296,8 @@ struct CadFeature {
              xf_translate, xf_axis, xf_pivot, xf_angle_deg, xf_copy,
              thicken_face, thicken_thickness, thicken_flip,
              cut_face_body, cut_face,
-             project_source_body, project_edges, project_face);
+             project_source_body, project_edges, project_face,
+             delete_faces);
     }
     template<class Archive>
     void load(Archive& ar) {
@@ -323,7 +328,8 @@ struct CadFeature {
             xf_translate, xf_axis, xf_pivot, xf_angle_deg, xf_copy,
             thicken_face, thicken_thickness, thicken_flip,
             cut_face_body, cut_face,
-            project_source_body, project_edges, project_face);
+             project_source_body, project_edges, project_face,
+             delete_faces);
         imported_solid = brep_from_string(brep);
     }
 };
@@ -446,6 +452,8 @@ public:
     // Offset face `face` of `target_body` by `thickness` along its normal, producing a new
     // thin solid appended as a new body. flip=true offsets against the normal.
     int add_thicken(int target_body, int face, double thickness, bool flip, const std::string& name);
+    int add_delete_face(int target_body, const std::vector<int>& faces,
+                        const std::string& name);
     // Datum plane: derived from base (0=XY/1=XZ/2=YZ/3+N=Nth earlier datum), offset
     // along its normal, optional tilt about a base axis. Produces no solid.
     int  add_plane(int base, double offset, double angle_tilt, int axis,

src/slic3r/GUI/McpControl.cpp

@@ -249,13 +249,18 @@ json describe_tools()
                      json{{"name", "keep_upper"},{"type", "boolean"}, {"default", true}},
                      json{{"name", "keep_lower"},{"type", "boolean"}, {"default", true}},
                  })}},
-            json{{"name", "project"}, {"summary", "Project edges of a solid onto a sketch plane, producing a new sketch feature."},
-                 {"params", json::array({
-                     json{{"name", "source_body"}, {"type", "integer"}, {"default", -1}, {"description", "body owning the edges; -1 = last body"}},
-                     json{{"name", "face"},        {"type", "integer"}, {"default", -1}, {"description", "global face id on the source body; when set, all its edges are projected"}},
-                     json{{"name", "edges"},       {"type", "array"}, {"default", json::array()}, {"description", "global edge ids to project; empty => project the face"}},
-                     json{{"name", "plane"},       {"type", "string"}, {"default", "XY"}, {"description", "target sketch plane (XY/XZ/YZ)"}},
-                 })}},
+             json{{"name", "project"}, {"summary", "Project edges of a solid onto a sketch plane, producing a new sketch feature."},
+                  {"params", json::array({
+                      json{{"name", "source_body"}, {"type", "integer"}, {"default", -1}, {"description", "body owning the edges; -1 = last body"}},
+                      json{{"name", "face"},        {"type", "integer"}, {"default", -1}, {"description", "global face id on the source body; when set, all its edges are projected"}},
+                      json{{"name", "edges"},       {"type", "array"}, {"default", json::array()}, {"description", "global edge ids to project; empty => project the face"}},
+                      json{{"name", "plane"},       {"type", "string"}, {"default", "XY"}, {"description", "target sketch plane (XY/XZ/YZ)"}},
+                  })}},
+             json{{"name", "delete_face"}, {"summary", "Remove faces from a solid, healing the gap via OCCT defeaturing."},
+                  {"params", json::array({
+                      json{{"name", "body"},  {"type", "integer"}, {"default", -1}, {"description", "target body; omit for the last body"}},
+                      json{{"name", "faces"}, {"type", "array"}, {"description", "global face ids to delete"}},
+                  })}},
             json{{"name", "bridge"}, {"summary", "Build a cubic-Bezier G1 bridge (BSpline) between two sketch-entity endpoints within a sketch feature."},
                   {"params", json::array({
                       json{{"name", "sketch"}, {"type", "integer"}, {"description", "sketch feature index"}},
@@ -966,6 +971,23 @@ json action_project(DesignPanel* panel, const json& params)
     return json{{"ok", ok}, {"project_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
 }
 
+json action_delete_face(DesignPanel* panel, const json& params)
+{
+    if (!params.contains("faces")) throw std::runtime_error("delete_face needs 'faces' (array of face ids)");
+    CadDocument& doc = panel->mcp_doc();
+    if (doc.bodies.empty()) throw std::runtime_error("no body to delete faces from");
+    int bi = target_body_arg(params, doc);
+    std::vector<int> faces;
+    if (params["faces"].is_array())
+        for (const auto& v : params["faces"]) faces.push_back(v.get<int>());
+    doc.checkpoint();
+    int idx = doc.add_delete_face(bi, faces, "DeleteFace");
+    bool ok = doc.recompute();
+    if (!ok) doc.undo();
+    panel->mcp_after_change();
+    return json{{"ok", ok}, {"feature_index", idx}, {"bodies", int(doc.bodies.size())}, {"error", doc.error}};
+}
+
 json action_bridge(DesignPanel* panel, const json& params)
 {
     if (!params.contains("sketch")) throw std::runtime_error("bridge needs 'sketch' (feature index)");
@@ -1088,6 +1110,7 @@ std::string handle_on_main(const std::string& method, const json& params, const
         if (method == "thicken")        return rpc_result(id, action_thicken(panel, params));
         if (method == "split")          return rpc_result(id, action_split(panel, params));
         if (method == "project")        return rpc_result(id, action_project(panel, params));
+        if (method == "delete_face")    return rpc_result(id, action_delete_face(panel, params));
         if (method == "bridge")         return rpc_result(id, action_bridge(panel, params));
         if (method == "axis")           return rpc_result(id, action_axis(panel, params));
         if (method == "coordsys")       return rpc_result(id, action_coordsys(panel, params));

tests/libslic3r/test_caddocument.cpp

@@ -3939,3 +3939,112 @@ TEST_CASE("bridge round-trip serialization", "[CadDocument][bridge]")
     REQUIRE_THAT(br.ctrl.back().x(), WithinAbs(20.0, 1e-9));
     REQUIRE_THAT(br.ctrl.back().y(), WithinAbs(0.0, 1e-9));
 }
+
+TEST_CASE("delete_face removes a fillet face and restores volume", "[CadDocument][deleteface]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    double Vbox = double(doc.display_mesh.volume());
+    REQUIRE(Vbox > 0.0);
+
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+    double Vf = double(doc.display_mesh.volume());
+    REQUIRE(Vf < Vbox);
+
+    int nfaces = GeometryEngine::face_count(doc.bodies[0].shape);
+    doc.checkpoint();
+    bool found = false;
+    for (int fi = 0; fi < nfaces && !found; ++fi) {
+        int idx = doc.add_delete_face(0, {fi}, "Unfillet");
+        (void)idx;
+        if (doc.recompute() && doc.error.empty()) {
+            double Vr = double(doc.display_mesh.volume());
+            if (Vr > Vf) {
+                found = true;
+            }
+        }
+        if (!found) doc.undo();
+    }
+    REQUIRE(found);
+}
+
+TEST_CASE("delete_face with bad face index fails safely", "[CadDocument][deleteface]")
+{
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    doc.add_delete_face(0, {9999}, "Bad");
+    REQUIRE_FALSE(doc.recompute());
+    REQUIRE_THAT(doc.error, Catch::Matchers::Contains("face"));
+}
+
+TEST_CASE("delete_face round-trip serialization", "[CadDocument][deleteface]")
+{
+    using Catch::Matchers::WithinRel;
+    using Catch::Matchers::WithinAbs;
+
+    CadDocument doc;
+    int sk = doc.add_sketch(SketchShape::Rectangle, SketchPlane::XY(), 20, 20, 10, "Box");
+    REQUIRE(sk >= 0);
+    doc.add_extrude(sk, 10.0, false, BooleanMode::New, "Extrude");
+    doc.add_fillet(2.0, FaceGroup::All, "Fillet");
+    REQUIRE(doc.recompute());
+    REQUIRE(doc.error.empty());
+
+    int nfaces = GeometryEngine::face_count(doc.bodies[0].shape);
+    int fillet_face = -1;
+    for (int fi = 0; fi < nfaces; ++fi) {
+        doc.checkpoint();
+        doc.add_delete_face(0, {fi}, "Unfillet");
+        bool ok = doc.recompute();
+        if (ok && doc.error.empty()) {
+            fillet_face = fi;
+            break;
+        }
+        doc.undo();
+    }
+    REQUIRE(fillet_face >= 0);
+
+    std::vector<std::pair<Vec3d, Vec3d>> bboxes;
+    for (const auto& b : doc.bodies) {
+        Bnd_Box bb; BRepBndLib::Add(b.shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        bboxes.push_back({Vec3d(x0, y0, z0), Vec3d(x1, y1, z1)});
+    }
+
+    auto blob = doc.serialize_recipe();
+    REQUIRE_FALSE(blob.empty());
+
+    CadDocument doc2;
+    REQUIRE(doc2.deserialize_recipe(blob));
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.recompute());
+    REQUIRE(doc2.error.empty());
+    REQUIRE(doc2.bodies.size() == doc.bodies.size());
+
+    for (size_t i = 0; i < bboxes.size(); ++i) {
+        Bnd_Box bb; BRepBndLib::Add(doc2.bodies[i].shape, bb);
+        Standard_Real x0, y0, z0, x1, y1, z1;
+        bb.Get(x0, y0, z0, x1, y1, z1);
+        REQUIRE_THAT(double(x0), WithinAbs(bboxes[i].first.x(),  1e-6));
+        REQUIRE_THAT(double(y0), WithinAbs(bboxes[i].first.y(),  1e-6));
+        REQUIRE_THAT(double(z0), WithinAbs(bboxes[i].first.z(),  1e-6));
+        REQUIRE_THAT(double(x1), WithinAbs(bboxes[i].second.x(), 1e-6));
+        REQUIRE_THAT(double(y1), WithinAbs(bboxes[i].second.y(), 1e-6));
+        REQUIRE_THAT(double(z1), WithinAbs(bboxes[i].second.z(), 1e-6));
+    }
+}