feat: LOFT command — ruled-surface loft through multiple cross-sections

Picks 2+ profile entities (closed or open wires), builds ruled shells
between consecutive pairs via builder::try_wire_homotopy, caps closed
ends with planar faces, and tessellates the result into a Solid3D mesh.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/cmd_result.rs

@@ -1107,6 +1107,75 @@ impl H7CAD {
                 self.restore_pre_cmd_tangent();
             }
 
+            // ── LOFT ───────────────────────────────────────────────────────
+            CmdResult::LoftEntities { handles, color } => {
+                use crate::entities::traits::EntityTypeOps;
+                use crate::scene::acad_to_truck::TruckObject;
+                use crate::scene::truck_tess;
+                use crate::modules::insert::solid3d_cmds::empty_solid3d;
+                use truck_modeling::builder;
+
+                // Collect wires from each profile.
+                let mut wires: Vec<truck_modeling::Wire> = Vec::new();
+                for h in &handles {
+                    if let Some(ent) = self.tabs[i].scene.document.get_entity(*h).cloned() {
+                        if let Some(te) = ent.to_truck_entity(&self.tabs[i].scene.document) {
+                            let wire = match te.object {
+                                TruckObject::Contour(w) => Some(w),
+                                TruckObject::Curve(e)   => Some(std::iter::once(e).collect()),
+                                _ => None,
+                            };
+                            if let Some(w) = wire { wires.push(w); }
+                        }
+                    }
+                }
+
+                let result: Option<crate::scene::mesh_model::MeshModel> = (|| {
+                    if wires.len() < 2 { return None; }
+
+                    // Build ruled shells between consecutive profile pairs.
+                    let mut all_faces: Vec<truck_modeling::Face> = Vec::new();
+
+                    for pair in wires.windows(2) {
+                        let shell = builder::try_wire_homotopy(&pair[0], &pair[1]).ok()?;
+                        for face in shell.into_iter() { all_faces.push(face); }
+                    }
+
+                    // Cap the first and last profiles if they are closed.
+                    if let Ok(cap) = builder::try_attach_plane(&[wires.first()?.clone()]) {
+                        all_faces.push(cap);
+                    }
+                    if let Ok(cap) = builder::try_attach_plane(&[wires.last()?.clone()]) {
+                        all_faces.push(cap);
+                    }
+
+                    let shell = truck_modeling::Shell::from(all_faces);
+                    match truck_tess::tessellate_shell(&shell) {
+                        truck_tess::TruckTessResult::Mesh { verts, normals, indices } =>
+                            Some(crate::scene::mesh_model::MeshModel {
+                                name: String::new(), verts, normals, indices, color, selected: false,
+                            }),
+                        _ => None,
+                    }
+                })();
+
+                if let Some(mut mesh) = result {
+                    self.push_undo_snapshot(i, "LOFT");
+                    let new_entity = empty_solid3d();
+                    let new_handle = self.tabs[i].scene.add_entity(new_entity);
+                    mesh.name = format!("{}", new_handle.value());
+                    self.tabs[i].scene.meshes.insert(new_handle, mesh);
+                    self.tabs[i].dirty = true;
+                    self.command_line.push_output(&format!("LOFT: solid created from {} profiles.", handles.len()));
+                } else {
+                    self.command_line.push_error("LOFT: could not loft profiles. Ensure sections have the same edge count and are compatible.");
+                }
+                self.tabs[i].active_cmd = None;
+                self.tabs[i].snap_result = None;
+                self.tabs[i].scene.clear_preview_wire();
+                self.restore_pre_cmd_tangent();
+            }
+
             CmdResult::HatcheditApply { handle, name, scale, angle } => {
                 if let Some(mut model) = self.tabs[i].scene.hatches.get(&handle).cloned() {
                     // Update model fields

src/app/commands.rs

@@ -3466,6 +3466,15 @@ impl H7CAD {
                 self.tabs[i].active_cmd = Some(Box::new(cmd));
             }
 
+            // ── LOFT ───────────────────────────────────────────────────────
+            "LOFT" => {
+                use crate::modules::insert::solid3d_cmds::LoftCommand;
+                let color = self.tabs[i].scene.layer_color(&self.tabs[i].active_layer);
+                let cmd = LoftCommand::new(color);
+                self.command_line.push_info(&cmd.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(cmd));
+            }
+
             // ── OBJ import ───────────────────────────────────────────────
             "IMPORTOBJ"|"OBJIMPORT" => {
                 return Task::done(Message::ObjImport);

src/command/mod.rs

@@ -159,6 +159,11 @@ pub enum CmdResult {
         path_handle: Handle,
         color: [f32; 4],
     },
+    /// Loft through a series of profile entities.
+    LoftEntities {
+        handles: Vec<Handle>,
+        color: [f32; 4],
+    },
     /// INSERT landed on a block that has AttributeDefinitions.
     /// The host should look up the attdefs for `block_name` from the document
     /// and call `attreq_set_attdefs()` on the command, then loop on text input.

src/modules/insert/solid3d_cmds.rs

@@ -415,6 +415,49 @@ impl CadCommand for SweepCommand {
     fn on_enter(&mut self) -> CmdResult { CmdResult::Cancel }
 }
 
+// ── LOFT command ───────────────────────────────────────────────────────────
+
+pub struct LoftCommand {
+    profiles: Vec<acadrust::Handle>,
+    color: [f32; 4],
+}
+
+impl LoftCommand {
+    pub fn new(color: [f32; 4]) -> Self {
+        Self { profiles: Vec::new(), color }
+    }
+}
+
+impl CadCommand for LoftCommand {
+    fn name(&self) -> &'static str { "LOFT" }
+    fn prompt(&self) -> String {
+        if self.profiles.is_empty() {
+            "LOFT  Select first cross-section:".into()
+        } else {
+            format!("LOFT  Select next cross-section ({} selected, Enter to finish):", self.profiles.len())
+        }
+    }
+    fn needs_entity_pick(&self) -> bool { true }
+    fn on_entity_pick(&mut self, handle: acadrust::Handle, _pt: Vec3) -> CmdResult {
+        if handle.is_null() { return CmdResult::NeedPoint; }
+        // Avoid duplicate picks.
+        if !self.profiles.contains(&handle) {
+            self.profiles.push(handle);
+        }
+        CmdResult::NeedPoint
+    }
+    fn on_point(&mut self, _pt: Vec3) -> CmdResult { CmdResult::NeedPoint }
+    fn wants_text_input(&self) -> bool { self.profiles.len() >= 2 }
+    fn on_text_input(&mut self, _text: &str) -> Option<CmdResult> { None }
+    fn on_enter(&mut self) -> CmdResult {
+        if self.profiles.len() < 2 {
+            CmdResult::Cancel
+        } else {
+            CmdResult::LoftEntities { handles: self.profiles.clone(), color: self.color }
+        }
+    }
+}
+
 // ── Placeholder Solid3D entity construction ────────────────────────────────
 
 /// Create a minimal Solid3D entity with empty ACIS data (placeholder only).