feat(commands): expand standard CAD command coverage

Integrate a large batch of standard CAD commands and fix several
name/behaviour mismatches, with no product references in code.

3D solids (reusing the truck B-rep pipeline):
- SLICE, INTERFERE, PRESSPULL, POLYSOLID, PYRAMID, SECTION
- 3DROTATE, 3DMIRROR, 3DALIGN (cached-solid transforms)

Annotation / text:
- ARCTEXT, SPLINEFIT (Catmull-Rom to Bezier), DIMJOGGED, OBJECTSCALE
  (XData markers honoured by the existing geometry-gen / tessellator)

Blocks / misc:
- NCOPY (block-content extraction via explode_entity)
- OPTIONS, SYNCPVIEWPORTS, THICKEN, plus earlier toggles, aliases,
  system variables, and layer/style/view commands

POINTCLOUD/RECAP and UNDERLAYLAYERS/UOSNAP are intentionally left out:
they require a proprietary binary / PDF-layer parser, a GPU point
renderer, and real test files.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/model_ops.rs

@@ -37,9 +37,8 @@ impl super::OpenCADStudio {
             .filter(|h| self.tabs[i].scene.solid_models.contains_key(h))
             .collect();
         if handles.len() != 2 {
-            self.command_line.push_error(
-                "Boolean: select exactly two solids created this session.",
-            );
+            self.command_line
+                .push_error("Boolean: select exactly two solids created this session.");
             return Task::none();
         }
         let a = self.tabs[i].scene.solid_models[&handles[0]].clone();
@@ -72,4 +71,681 @@ impl super::OpenCADStudio {
         self.refresh_properties();
         Task::none()
     }
+
+    /// Slice the one selected solid with an axis-aligned plane (axis 0/1/2 =
+    /// X/Y/Z at `value`), keeping the lower side when `keep_low` is true. The
+    /// kept half is the intersection of the solid with a half-space box, reusing
+    /// the same truck-shapeops path as the boolean tools.
+    pub(super) fn solid_slice(&mut self, axis: usize, value: f64, keep_low: bool) -> Task<Message> {
+        let i = self.active_tab;
+        let handles: Vec<Handle> = self.tabs[i]
+            .scene
+            .selected
+            .iter()
+            .copied()
+            .filter(|h| self.tabs[i].scene.solid_models.contains_key(h))
+            .collect();
+        if handles.len() != 1 {
+            self.command_line
+                .push_error("SLICE: select exactly one solid created this session.");
+            return Task::none();
+        }
+        let solid = self.tabs[i].scene.solid_models[&handles[0]].clone();
+        // Bounding box from the solid's edge wires.
+        let wires = solid_model::edge_wires(&solid);
+        let (mut min, mut max) = ([f64::MAX; 3], [f64::MIN; 3]);
+        for w in &wires {
+            for p in &w.points {
+                let c = [p.x, p.y, p.z];
+                for k in 0..3 {
+                    min[k] = min[k].min(c[k]);
+                    max[k] = max[k].max(c[k]);
+                }
+            }
+        }
+        if min[0] > max[0] {
+            self.command_line
+                .push_error("SLICE: could not determine the solid's extent.");
+            return Task::none();
+        }
+        // Generous margin so the box fully spans the solid in the free axes.
+        let m = [
+            (max[0] - min[0]).max(1.0),
+            (max[1] - min[1]).max(1.0),
+            (max[2] - min[2]).max(1.0),
+        ];
+        let mut lo = [min[0] - m[0], min[1] - m[1], min[2] - m[2]];
+        let mut hi = [max[0] + m[0], max[1] + m[1], max[2] + m[2]];
+        if keep_low {
+            hi[axis] = value;
+        } else {
+            lo[axis] = value;
+        }
+        if hi[axis] <= lo[axis] {
+            self.command_line
+                .push_error("SLICE: the plane does not cross the solid on the kept side.");
+            return Task::none();
+        }
+        let center = [
+            (lo[0] + hi[0]) / 2.0,
+            (lo[1] + hi[1]) / 2.0,
+            (lo[2] + hi[2]) / 2.0,
+        ];
+        let halfspace = solid_model::box_solid(center, hi[0] - lo[0], hi[1] - lo[1], hi[2] - lo[2]);
+        let Some(result) = solid_model::boolean(Bool::Intersect, &solid, &halfspace) else {
+            self.command_line
+                .push_error("SLICE failed — the plane may not cross the solid.");
+            return Task::none();
+        };
+        self.push_undo_snapshot(i, "SLICE");
+        self.tabs[i].scene.erase_entities(&handles);
+        let mut s3d = Solid3D::new();
+        s3d.wires = solid_model::edge_wires(&result);
+        let handle = self.add_solid_model(EntityType::Solid3D(s3d), result);
+        self.tabs[i].scene.deselect_all();
+        if !handle.is_null() {
+            self.tabs[i].scene.select_entity(handle, false);
+        }
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        let ax = ["X", "Y", "Z"][axis];
+        self.command_line.push_output(&format!(
+            "SLICE: cut at {ax}={value}, kept the {} half.",
+            if keep_low { "lower" } else { "upper" }
+        ));
+        Task::none()
+    }
+
+    /// INTERFERE — create a solid from the overlap of the two selected solids,
+    /// leaving the originals in place (a non-destructive boolean intersect).
+    pub(super) fn solid_interfere(&mut self) -> Task<Message> {
+        let i = self.active_tab;
+        let handles: Vec<Handle> = self.tabs[i]
+            .scene
+            .selected
+            .iter()
+            .copied()
+            .filter(|h| self.tabs[i].scene.solid_models.contains_key(h))
+            .collect();
+        if handles.len() != 2 {
+            self.command_line
+                .push_error("INTERFERE: select exactly two solids created this session.");
+            return Task::none();
+        }
+        let a = self.tabs[i].scene.solid_models[&handles[0]].clone();
+        let b = self.tabs[i].scene.solid_models[&handles[1]].clone();
+        match solid_model::boolean(Bool::Intersect, &a, &b) {
+            Some(result) => {
+                self.push_undo_snapshot(i, "INTERFERE");
+                // Keep both originals; add the interference solid.
+                let mut s3d = Solid3D::new();
+                s3d.wires = solid_model::edge_wires(&result);
+                self.add_solid_model(EntityType::Solid3D(s3d), result);
+                self.tabs[i].dirty = true;
+                self.refresh_properties();
+                self.command_line
+                    .push_output("INTERFERE: created an interference solid from the overlap.");
+            }
+            None => self
+                .command_line
+                .push_output("INTERFERE: the selected solids do not overlap."),
+        }
+        Task::none()
+    }
+
+    /// 3DROTATE — rotate the one selected solid about the X/Y/Z axis (0/1/2)
+    /// through its centre by `angle_deg` degrees. Rotation preserves the solid's
+    /// orientation, so it reuses the cached truck B-rep directly.
+    pub(super) fn solid_rotate3d(&mut self, axis: usize, angle_deg: f64) -> Task<Message> {
+        use truck_modeling::{builder, Point3, Rad, Vector3 as TVec3};
+        let i = self.active_tab;
+        let handles: Vec<Handle> = self.tabs[i]
+            .scene
+            .selected
+            .iter()
+            .copied()
+            .filter(|h| self.tabs[i].scene.solid_models.contains_key(h))
+            .collect();
+        if handles.len() != 1 {
+            self.command_line
+                .push_error("3DROTATE: select exactly one solid created this session.");
+            return Task::none();
+        }
+        let solid = self.tabs[i].scene.solid_models[&handles[0]].clone();
+        let wires = solid_model::edge_wires(&solid);
+        let (mut min, mut max) = ([f64::MAX; 3], [f64::MIN; 3]);
+        for w in &wires {
+            for p in &w.points {
+                let c = [p.x, p.y, p.z];
+                for k in 0..3 {
+                    min[k] = min[k].min(c[k]);
+                    max[k] = max[k].max(c[k]);
+                }
+            }
+        }
+        if min[0] > max[0] {
+            self.command_line
+                .push_error("3DROTATE: could not determine the solid's extent.");
+            return Task::none();
+        }
+        let origin = Point3::new(
+            (min[0] + max[0]) / 2.0,
+            (min[1] + max[1]) / 2.0,
+            (min[2] + max[2]) / 2.0,
+        );
+        let axis_v = match axis {
+            0 => TVec3::unit_x(),
+            1 => TVec3::unit_y(),
+            _ => TVec3::unit_z(),
+        };
+        let rotated = builder::rotated(&solid, origin, axis_v, Rad(angle_deg.to_radians()));
+        self.push_undo_snapshot(i, "3DROTATE");
+        self.tabs[i].scene.erase_entities(&handles);
+        let mut s3d = Solid3D::new();
+        s3d.wires = solid_model::edge_wires(&rotated);
+        let handle = self.add_solid_model(EntityType::Solid3D(s3d), rotated);
+        self.tabs[i].scene.deselect_all();
+        if !handle.is_null() {
+            self.tabs[i].scene.select_entity(handle, false);
+        }
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        self.command_line.push_output(&format!(
+            "3DROTATE: rotated {angle_deg}° about the {} axis.",
+            ["X", "Y", "Z"][axis]
+        ));
+        Task::none()
+    }
+
+    /// POLYSOLID — build a wall-like solid from a selected polyline: one box per
+    /// segment (oriented along it, `width` wide, `height` tall) unioned together,
+    /// reusing the box primitive + the boolean union path.
+    pub(super) fn solid_polysolid(&mut self, width: f64, height: f64) -> Task<Message> {
+        use truck_modeling::{builder, Point3, Rad, Vector3 as TVec3};
+        let i = self.active_tab;
+        let found: Option<(Handle, Vec<[f64; 2]>, bool)> = self.tabs[i]
+            .scene
+            .selected_entities()
+            .iter()
+            .find_map(|(h, e)| match e {
+                EntityType::LwPolyline(pl) => Some((
+                    *h,
+                    pl.vertices
+                        .iter()
+                        .map(|v| [v.location.x, v.location.y])
+                        .collect(),
+                    pl.is_closed,
+                )),
+                _ => None,
+            });
+        let Some((handle, pts, closed)) = found else {
+            self.command_line
+                .push_error("POLYSOLID: select a polyline first.");
+            return Task::none();
+        };
+        let mut segs: Vec<([f64; 2], [f64; 2])> = pts.windows(2).map(|w| (w[0], w[1])).collect();
+        if closed && pts.len() > 2 {
+            segs.push((pts[pts.len() - 1], pts[0]));
+        }
+        let mut acc: Option<Solid> = None;
+        let mut used = 0usize;
+        for (a, b) in &segs {
+            let (dx, dy) = (b[0] - a[0], b[1] - a[1]);
+            let len = (dx * dx + dy * dy).sqrt();
+            if len < 1e-9 {
+                continue;
+            }
+            let angle = dy.atan2(dx);
+            // Local box: X 0..len, Y -w/2..w/2, Z 0..h, then orient to the segment.
+            let bx = solid_model::box_solid([len / 2.0, 0.0, height / 2.0], len, width, height);
+            let bx = builder::rotated(&bx, Point3::new(0.0, 0.0, 0.0), TVec3::unit_z(), Rad(angle));
+            let bx = builder::translated(&bx, TVec3::new(a[0], a[1], 0.0));
+            acc = Some(match acc {
+                None => bx,
+                Some(prev) => solid_model::boolean(Bool::Union, &prev, &bx).unwrap_or(prev),
+            });
+            used += 1;
+        }
+        let Some(result) = acc else {
+            self.command_line
+                .push_error("POLYSOLID: the polyline has no usable segments.");
+            return Task::none();
+        };
+        self.push_undo_snapshot(i, "POLYSOLID");
+        self.tabs[i].scene.erase_entities(&[handle]);
+        let mut s3d = Solid3D::new();
+        s3d.wires = solid_model::edge_wires(&result);
+        let h = self.add_solid_model(EntityType::Solid3D(s3d), result);
+        self.tabs[i].scene.deselect_all();
+        if !h.is_null() {
+            self.tabs[i].scene.select_entity(h, false);
+        }
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        self.command_line.push_output(&format!(
+            "POLYSOLID: built a wall solid from {used} segment(s) (width {width}, height {height})."
+        ));
+        Task::none()
+    }
+
+    /// 3DMIRROR — add a mirrored copy of the one selected solid across the plane
+    /// perpendicular to the X/Y/Z axis (0/1/2) through its centre, keeping the
+    /// original. Reflection reverses face orientation, so `Solid::not()` restores
+    /// outward normals (the same inversion the boolean subtraction relies on).
+    pub(super) fn solid_mirror3d(&mut self, axis: usize) -> Task<Message> {
+        use truck_modeling::{builder, Matrix4, Vector3 as TVec3};
+        let i = self.active_tab;
+        let handles: Vec<Handle> = self.tabs[i]
+            .scene
+            .selected
+            .iter()
+            .copied()
+            .filter(|h| self.tabs[i].scene.solid_models.contains_key(h))
+            .collect();
+        if handles.len() != 1 {
+            self.command_line
+                .push_error("3DMIRROR: select exactly one solid created this session.");
+            return Task::none();
+        }
+        let solid = self.tabs[i].scene.solid_models[&handles[0]].clone();
+        let wires = solid_model::edge_wires(&solid);
+        let (mut min, mut max) = ([f64::MAX; 3], [f64::MIN; 3]);
+        for w in &wires {
+            for p in &w.points {
+                let c = [p.x, p.y, p.z];
+                for k in 0..3 {
+                    min[k] = min[k].min(c[k]);
+                    max[k] = max[k].max(c[k]);
+                }
+            }
+        }
+        if min[0] > max[0] {
+            self.command_line
+                .push_error("3DMIRROR: could not determine the solid's extent.");
+            return Task::none();
+        }
+        let c = TVec3::new(
+            (min[0] + max[0]) / 2.0,
+            (min[1] + max[1]) / 2.0,
+            (min[2] + max[2]) / 2.0,
+        );
+        let s = match axis {
+            0 => TVec3::new(-1.0, 1.0, 1.0),
+            1 => TVec3::new(1.0, -1.0, 1.0),
+            _ => TVec3::new(1.0, 1.0, -1.0),
+        };
+        // Reflect about the plane through the centre: T(c) · scale · T(-c).
+        let mat = Matrix4::from_translation(c)
+            * Matrix4::from_nonuniform_scale(s.x, s.y, s.z)
+            * Matrix4::from_translation(-c);
+        let mut reflected = builder::transformed(&solid, mat);
+        reflected.not(); // restore outward orientation after the reflection
+        self.push_undo_snapshot(i, "3DMIRROR");
+        let mut s3d = Solid3D::new();
+        s3d.wires = solid_model::edge_wires(&reflected);
+        let h = self.add_solid_model(EntityType::Solid3D(s3d), reflected);
+        self.tabs[i].scene.deselect_all();
+        if !h.is_null() {
+            self.tabs[i].scene.select_entity(h, false);
+        }
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        self.command_line.push_output(&format!(
+            "3DMIRROR: added a mirror across the {} plane.",
+            ["X", "Y", "Z"][axis]
+        ));
+        Task::none()
+    }
+
+    /// 3DALIGN — move/rotate the one selected solid so its three source points
+    /// land on the three destination points. The frame-to-frame transform is
+    /// computed in glam (`M = D · S⁻¹`) and handed to truck as a raw matrix; both
+    /// frames are right-handed so the result is a pure rotation+translation.
+    pub(super) fn solid_align3d(
+        &mut self,
+        src: [[f64; 3]; 3],
+        dst: [[f64; 3]; 3],
+    ) -> Task<Message> {
+        use truck_modeling::{builder, Matrix4};
+        let i = self.active_tab;
+        let handles: Vec<Handle> = self.tabs[i]
+            .scene
+            .selected
+            .iter()
+            .copied()
+            .filter(|h| self.tabs[i].scene.solid_models.contains_key(h))
+            .collect();
+        if handles.len() != 1 {
+            self.command_line
+                .push_error("3DALIGN: select exactly one solid created this session.");
+            return Task::none();
+        }
+        // Build a right-handed frame (origin + orthonormal axes) from 3 points.
+        let frame = |p: [[f64; 3]; 3]| -> Option<glam::DMat4> {
+            let p1 = glam::DVec3::from_array(p[0]);
+            let p2 = glam::DVec3::from_array(p[1]);
+            let p3 = glam::DVec3::from_array(p[2]);
+            let x = (p2 - p1).normalize_or_zero();
+            let z = (p2 - p1).cross(p3 - p1).normalize_or_zero();
+            if x.length_squared() < 1e-12 || z.length_squared() < 1e-12 {
+                return None; // coincident or collinear points
+            }
+            let y = z.cross(x);
+            Some(glam::DMat4::from_cols(
+                x.extend(0.0),
+                y.extend(0.0),
+                z.extend(0.0),
+                p1.extend(1.0),
+            ))
+        };
+        let (Some(s), Some(d)) = (frame(src), frame(dst)) else {
+            self.command_line
+                .push_error("3DALIGN: each point triple must be non-coincident and non-collinear.");
+            return Task::none();
+        };
+        let a = (d * s.inverse()).to_cols_array(); // column-major [f64; 16]
+        let mat = Matrix4::new(
+            a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11], a[12], a[13],
+            a[14], a[15],
+        );
+        let solid = self.tabs[i].scene.solid_models[&handles[0]].clone();
+        let aligned = builder::transformed(&solid, mat);
+        self.push_undo_snapshot(i, "3DALIGN");
+        self.tabs[i].scene.erase_entities(&handles);
+        let mut s3d = Solid3D::new();
+        s3d.wires = solid_model::edge_wires(&aligned);
+        let h = self.add_solid_model(EntityType::Solid3D(s3d), aligned);
+        self.tabs[i].scene.deselect_all();
+        if !h.is_null() {
+            self.tabs[i].scene.select_entity(h, false);
+        }
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        self.command_line
+            .push_output("3DALIGN: aligned the solid to the destination points.");
+        Task::none()
+    }
+
+    /// SECTION — draw the cross-section outline where an axis-aligned plane
+    /// (X/Y/Z = `axis` at `value`) cuts the one selected solid, as Line entities.
+    /// Reuses the mesh-interference analyzer to find the cut segments.
+    pub(super) fn solid_section(&mut self, axis: usize, value: f64) -> Task<Message> {
+        use acadrust::types::Vector3;
+        use acadrust::Line;
+        use truck_meshalgo::analyzers::Collision;
+        use truck_meshalgo::tessellation::{MeshableShape, MeshedShape};
+        use truck_modeling::{builder, Point3, Shell, Wire};
+
+        let i = self.active_tab;
+        let handles: Vec<Handle> = self.tabs[i]
+            .scene
+            .selected
+            .iter()
+            .copied()
+            .filter(|h| self.tabs[i].scene.solid_models.contains_key(h))
+            .collect();
+        if handles.len() != 1 {
+            self.command_line
+                .push_error("SECTION: select exactly one solid created this session.");
+            return Task::none();
+        }
+        let solid = self.tabs[i].scene.solid_models[&handles[0]].clone();
+        let wires = solid_model::edge_wires(&solid);
+        let (mut min, mut max) = ([f64::MAX; 3], [f64::MIN; 3]);
+        for w in &wires {
+            for p in &w.points {
+                let c = [p.x, p.y, p.z];
+                for k in 0..3 {
+                    min[k] = min[k].min(c[k]);
+                    max[k] = max[k].max(c[k]);
+                }
+            }
+        }
+        if min[0] > max[0] {
+            self.command_line
+                .push_error("SECTION: could not determine the solid's extent.");
+            return Task::none();
+        }
+        // Margin so the cutting plane fully spans the solid in the free axes.
+        let m = [
+            (max[0] - min[0]).max(1.0) * 0.1,
+            (max[1] - min[1]).max(1.0) * 0.1,
+            (max[2] - min[2]).max(1.0) * 0.1,
+        ];
+        let lo = [min[0] - m[0], min[1] - m[1], min[2] - m[2]];
+        let hi = [max[0] + m[0], max[1] + m[1], max[2] + m[2]];
+        let corners: [Point3; 4] = match axis {
+            0 => [
+                Point3::new(value, lo[1], lo[2]),
+                Point3::new(value, hi[1], lo[2]),
+                Point3::new(value, hi[1], hi[2]),
+                Point3::new(value, lo[1], hi[2]),
+            ],
+            1 => [
+                Point3::new(lo[0], value, lo[2]),
+                Point3::new(hi[0], value, lo[2]),
+                Point3::new(hi[0], value, hi[2]),
+                Point3::new(lo[0], value, hi[2]),
+            ],
+            _ => [
+                Point3::new(lo[0], lo[1], value),
+                Point3::new(hi[0], lo[1], value),
+                Point3::new(hi[0], hi[1], value),
+                Point3::new(lo[0], hi[1], value),
+            ],
+        };
+        let v: Vec<_> = corners.iter().map(|p| builder::vertex(*p)).collect();
+        let wire: Wire = vec![
+            builder::line(&v[0], &v[1]),
+            builder::line(&v[1], &v[2]),
+            builder::line(&v[2], &v[3]),
+            builder::line(&v[3], &v[0]),
+        ]
+        .into_iter()
+        .collect();
+        let Ok(face) = builder::try_attach_plane(&[wire]) else {
+            self.command_line
+                .push_error("SECTION: could not build the cutting plane.");
+            return Task::none();
+        };
+        let shell: Shell = std::iter::once(face).collect();
+        let tol = 0.02;
+        let solid_mesh = solid.triangulation(tol).to_polygon();
+        let plane_mesh = shell.triangulation(tol).to_polygon();
+        let segs = solid_mesh.extract_interference(&plane_mesh);
+        if segs.is_empty() {
+            self.command_line
+                .push_output("SECTION: the plane does not cross the solid.");
+            return Task::none();
+        }
+        self.push_undo_snapshot(i, "SECTION");
+        for (p1, p2) in &segs {
+            let line = Line::from_points(
+                Vector3::new(p1.x, p1.y, p1.z),
+                Vector3::new(p2.x, p2.y, p2.z),
+            );
+            self.tabs[i].scene.add_entity(EntityType::Line(line));
+        }
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        self.command_line.push_output(&format!(
+            "SECTION: created {} section line(s) at {}={value}.",
+            segs.len(),
+            ["X", "Y", "Z"][axis]
+        ));
+        Task::none()
+    }
+
+    /// PYRAMID — create an `n`-sided pyramid (regular polygon base of the given
+    /// circumradius, apex at `height`) as a tessellated mesh, reusing the same
+    /// face→Shell→mesh path as LOFT. Each face is independent, so no closed-shell
+    /// topology is required; the windings give outward normals.
+    pub(super) fn solid_pyramid(
+        &mut self,
+        radius: f64,
+        height: f64,
+        sides: usize,
+    ) -> Task<Message> {
+        use crate::modules::insert::solid3d_cmds::empty_solid3d;
+        use crate::scene::convert::truck_tess;
+        use crate::scene::model::mesh_model::MeshModel;
+        use truck_modeling::{builder, Point3, Shell, Wire};
+
+        let i = self.active_tab;
+        let n = sides.max(3);
+        if radius <= 0.0 || height <= 0.0 {
+            self.command_line
+                .push_error("PYRAMID: radius and height must be positive.");
+            return Task::none();
+        }
+        let corners: Vec<Point3> = (0..n)
+            .map(|k| {
+                let a = std::f64::consts::TAU * k as f64 / n as f64;
+                Point3::new(radius * a.cos(), radius * a.sin(), 0.0)
+            })
+            .collect();
+        let apex = builder::vertex(Point3::new(0.0, 0.0, height));
+        let mut faces = Vec::new();
+        // Base: reversed winding so the normal points down (outward at the base).
+        {
+            let bv: Vec<_> = corners.iter().rev().map(|p| builder::vertex(*p)).collect();
+            let wire: Wire = (0..n)
+                .map(|k| builder::line(&bv[k], &bv[(k + 1) % n]))
+                .collect();
+            if let Ok(f) = builder::try_attach_plane(&[wire]) {
+                faces.push(f);
+            }
+        }
+        // Side triangles [corner k, corner k+1, apex] → outward normals.
+        let sv: Vec<_> = corners.iter().map(|p| builder::vertex(*p)).collect();
+        for k in 0..n {
+            let k1 = (k + 1) % n;
+            let wire: Wire = vec![
+                builder::line(&sv[k], &sv[k1]),
+                builder::line(&sv[k1], &apex),
+                builder::line(&apex, &sv[k]),
+            ]
+            .into_iter()
+            .collect();
+            if let Ok(f) = builder::try_attach_plane(&[wire]) {
+                faces.push(f);
+            }
+        }
+        if faces.len() < n + 1 {
+            self.command_line
+                .push_error("PYRAMID: could not build all faces.");
+            return Task::none();
+        }
+        let shell = Shell::from(faces);
+        let color = self.tabs[i].scene.layer_color(&self.tabs[i].active_layer);
+        let truck_tess::TruckTessResult::Mesh {
+            verts,
+            verts_low,
+            normals,
+            indices,
+        } = truck_tess::tessellate_shell(&shell)
+        else {
+            self.command_line
+                .push_error("PYRAMID: tessellation failed.");
+            return Task::none();
+        };
+        if verts.is_empty() {
+            self.command_line
+                .push_error("PYRAMID: tessellation produced no geometry.");
+            return Task::none();
+        }
+        self.push_undo_snapshot(i, "PYRAMID");
+        let new_handle = self.tabs[i].scene.add_entity(empty_solid3d());
+        let mesh = MeshModel {
+            name: format!("{}", new_handle.value()),
+            verts,
+            verts_low,
+            normals,
+            indices,
+            color,
+            selected: false,
+        };
+        self.tabs[i]
+            .scene
+            .meshes
+            .insert(new_handle, crate::scene::MeshLodSet::from_single(mesh));
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        self.command_line.push_output(&format!(
+            "PYRAMID: created a {n}-sided pyramid (radius {radius}, height {height})."
+        ));
+        Task::none()
+    }
+
+    /// SPLINEFIT — replace the selected polyline with a cubic spline that passes
+    /// through its vertices. Control points come from the Catmull-Rom → cubic
+    /// Bézier formula (the curve provably interpolates each vertex), with a
+    /// clamped piecewise-Bézier knot vector the spline renderer reads directly.
+    pub(super) fn fit_spline(&mut self) -> Task<Message> {
+        use acadrust::entities::Spline;
+        use acadrust::types::Vector3;
+
+        let i = self.active_tab;
+        let found: Option<(Handle, Vec<[f64; 3]>)> = self.tabs[i]
+            .scene
+            .selected_entities()
+            .iter()
+            .find_map(|(h, e)| match e {
+                EntityType::LwPolyline(pl) => Some((
+                    *h,
+                    pl.vertices
+                        .iter()
+                        .map(|v| [v.location.x, v.location.y, 0.0])
+                        .collect(),
+                )),
+                _ => None,
+            });
+        let Some((handle, fit)) = found else {
+            self.command_line
+                .push_error("SPLINEFIT: select a polyline to fit a spline through.");
+            return Task::none();
+        };
+        if fit.len() < 3 {
+            self.command_line
+                .push_error("SPLINEFIT: need at least 3 points.");
+            return Task::none();
+        }
+        let n = fit.len();
+        let m = n - 1; // Bézier segments
+        let p = |k: usize| glam::DVec3::new(fit[k][0], fit[k][1], fit[k][2]);
+        // Catmull-Rom → cubic Bézier control points: [P0, b1,b2,P1, b1,b2,P2, …].
+        let mut ctrl: Vec<Vector3> = Vec::with_capacity(3 * m + 1);
+        ctrl.push(Vector3::new(fit[0][0], fit[0][1], 0.0));
+        for seg in 0..m {
+            let p0 = p(seg);
+            let p1 = p(seg + 1);
+            let prev = if seg > 0 { p(seg - 1) } else { p0 };
+            let next = if seg + 2 <= m { p(seg + 2) } else { p1 };
+            let b1 = p0 + (p1 - prev) / 6.0;
+            let b2 = p1 - (next - p0) / 6.0;
+            ctrl.push(Vector3::new(b1.x, b1.y, 0.0));
+            ctrl.push(Vector3::new(b2.x, b2.y, 0.0));
+            ctrl.push(Vector3::new(p1.x, p1.y, 0.0));
+        }
+        // Clamped piecewise-Bézier knots (degree 3): len == ctrl.len()+degree+1.
+        let mut knots: Vec<f64> = vec![0.0; 4];
+        for s in 1..m {
+            knots.extend_from_slice(&[s as f64, s as f64, s as f64]);
+        }
+        knots.extend_from_slice(&[m as f64; 4]);
+        let mut spl = Spline::new();
+        spl.degree = 3;
+        spl.control_points = ctrl;
+        spl.knots = knots;
+        spl.fit_points = fit.iter().map(|q| Vector3::new(q[0], q[1], 0.0)).collect();
+        // flags.rational defaults to false (non-rational) — exactly what we want.
+        self.push_undo_snapshot(i, "SPLINEFIT");
+        self.tabs[i].scene.erase_entities(&[handle]);
+        self.tabs[i].scene.add_entity(EntityType::Spline(spl));
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        self.command_line
+            .push_output(&format!("SPLINEFIT: fit a spline through {n} points."));
+        Task::none()
+    }
 }