M2: shell and draft (exact convex polyhedra from planes)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/doc/src/document.rs

@@ -228,6 +228,22 @@ pub enum FeatureKind {
         #[serde(default)]
         hole: HoleKind,
     },
+    /// Hollow a body leaving walls of `thickness`, removing the faces at the given points.
+    Shell {
+        faces: Vec<Vec3>,
+        thickness: String,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        body: Option<String>,
+    },
+    /// Tilt faces (at the given points) about a neutral plane, leaning toward `pull`.
+    Draft {
+        faces: Vec<Vec3>,
+        angle: String,
+        neutral: PlaneRef,
+        pull: Vec3,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        body: Option<String>,
+    },
     /// A construction plane (sketch placement, split tool).
     ConstructionPlane {
         plane: PlaneRef,
@@ -331,6 +347,8 @@ impl FeatureKind {
             FeatureKind::Mirror { .. } => "MirrorFeature",
             FeatureKind::ConstructionPlane { .. } => "ConstructionPlane",
             FeatureKind::Hole { .. } => "HoleFeature",
+            FeatureKind::Shell { .. } => "ShellFeature",
+            FeatureKind::Draft { .. } => "DraftFeature",
             FeatureKind::Split { .. } => "SplitBodyFeature",
             FeatureKind::Move { .. } => "MoveFeature",
         }
@@ -353,6 +371,8 @@ impl FeatureKind {
             FeatureKind::Mirror { .. } => "Mirror",
             FeatureKind::ConstructionPlane { .. } => "Plane",
             FeatureKind::Hole { .. } => "Hole",
+            FeatureKind::Shell { .. } => "Shell",
+            FeatureKind::Draft { .. } => "Draft",
             FeatureKind::Split { .. } => "Split",
             FeatureKind::Move { .. } => "Move",
         }
@@ -393,6 +413,11 @@ impl FeatureKind {
                 PatternKind::Circular { count, angle, .. } => v.extend([count.as_str(), angle]),
             },
             FeatureKind::Mirror { plane, .. } => plane_exprs(plane, &mut v),
+            FeatureKind::Shell { thickness, .. } => v.push(thickness),
+            FeatureKind::Draft { angle, neutral, .. } => {
+                v.push(angle);
+                plane_exprs(neutral, &mut v);
+            }
             FeatureKind::Hole { diameter, depth, hole, .. } => {
                 v.push(diameter);
                 v.extend(depth.iter().map(String::as_str));

crates/doc/src/eval.rs

@@ -472,6 +472,26 @@ fn extend_for_coplanar(st: &ModelState, plane: &Plane, r: &Region2, lo: f64, hi:
     (lo2, hi2)
 }
 
+/// The body a face-based feature applies to: by name, or the one whose surface is nearest the
+/// first point.
+fn body_at(st: &ModelState, body: &Option<String>, points: &[Vec3]) -> Result<usize> {
+    if let Some(n) = body {
+        return st.bodies.iter().position(|b| &b.name == n).ok_or_else(|| DocError::Unknown(format!("body `{n}`")));
+    }
+    let p = points.first().ok_or_else(|| DocError::Invalid("no faces selected".into()))?;
+    st.bodies
+        .iter()
+        .enumerate()
+        .map(|(i, b)| {
+            let bb = b.mesh().bounds();
+            let q = Vec3::new(p.x.clamp(bb.min.x, bb.max.x), p.y.clamp(bb.min.y, bb.max.y), p.z.clamp(bb.min.z, bb.max.z));
+            (i, q.dist(*p))
+        })
+        .min_by(|a, b| a.1.total_cmp(&b.1))
+        .map(|(i, _)| i)
+        .ok_or_else(|| DocError::Invalid("there is no body".into()))
+}
+
 /// The body a fillet/chamfer applies to: by name, or the one closest to the first edge point.
 fn blend_target(state: &ModelState, body: &Option<String>, edges: &[Vec3]) -> Result<usize> {
     if let Some(n) = body {
@@ -830,6 +850,27 @@ fn eval_feature(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature, st:
             let tools = feature_tools(vals, f, st)?;
             apply_op(st, f, tools, Operation::Cut, &[])
         }
+        FeatureKind::Shell { faces, thickness, body } => {
+            let t = val(vals, thickness, Kind::Length)?;
+            let i = body_at(st, body, faces)?;
+            let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
+            let nb = kernel::shell(&mb.body, faces, t)?;
+            if let Some(slot) = st.bodies.get_mut(i) {
+                *slot = ModelBody::new(mb.name, nb, mb.feature);
+            }
+            Ok(())
+        }
+        FeatureKind::Draft { faces, angle, neutral, pull, body } => {
+            let a = val(vals, angle, Kind::Angle)?;
+            let pl = doc.resolve_plane(vals, neutral, 0)?;
+            let i = body_at(st, body, faces)?;
+            let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
+            let nb = kernel::draft(&mb.body, faces, &pl, *pull, a)?;
+            if let Some(slot) = st.bodies.get_mut(i) {
+                *slot = ModelBody::new(mb.name, nb, mb.feature);
+            }
+            Ok(())
+        }
         FeatureKind::ConstructionPlane { plane } => {
             doc.resolve_plane(vals, plane, 0)?;
             Ok(())