diff --git a/src/crown_gear.rs b/src/crown_gear.rs
index 42333dd..40d3169 100644
--- a/src/crown_gear.rs
+++ b/src/crown_gear.rs
@@ -1,4 +1,4 @@
-use std::f32::consts::PI;
+use std::{f32::consts::PI, ops::Range};
 
 use glam::{Mat3A, Vec3, vec3};
 
@@ -20,6 +20,23 @@ pub struct CrownGearVisual {
 	pub base_thickness: f32,
 }
 
+impl CrownGearDesc {
+	pub fn to_shape(&self, part: Range<f32>, sides: usize) -> Vec<Vec3> {
+		let teeth = 2.0 * self.pitch_radius;
+		let mut ret = Vec::new();
+		ret.reserve_exact(sides);
+		for k in 0..sides {
+			let t0 = k as f32 / sides as f32;
+			let t = part.start + t0 * (part.end - part.start);
+			let rot = Mat3A::from_rotation_z(2.0 * PI * t);
+			let tooth = t * teeth;
+			let z = self.profile.y_from_tooth(tooth);
+			ret.push(rot * vec3(self.pitch_radius, 0.0, z));
+		}
+		ret
+	}
+}
+
 pub fn make_mesh_smooth(
 	desc: &CrownGearDesc,
 	visual: &CrownGearVisual,
@@ -85,28 +102,26 @@ pub fn make_mesh_simple(
 	visual: &CrownGearVisual,
 	sides: usize,
 ) -> MeshIndexed<Vec3> {
-	let teeth = 2.0 * desc.pitch_radius;
 	let inner_scale = visual.inner_radius / desc.pitch_radius;
 	let outer_scale = visual.outer_radius / desc.pitch_radius;
+	let shape = desc.to_shape(0.0..1.0, sides);
+	assert_eq!(shape.len(), sides);
 
 	let mut mesh = MeshIndexed::new();
 	mesh.vertices.reserve_exact(4 * sides);
 	mesh.faces.reserve_exact(8 * sides);
-	for k in 0..sides {
-		let t = k as f32 / sides as f32;
-		let rot = Mat3A::from_rotation_z(2.0 * PI * t);
-
-		let tooth = t * teeth;
-		let y = desc.profile.y_from_tooth(tooth);
-
-		let vertex = |x, z| rot * vec3(x, 0.0, z);
+	for pt in shape {
+		let inner = inner_scale * pt;
+		let outer = outer_scale * pt;
 		mesh.vertices.extend([
-			vertex(visual.inner_radius, -visual.base_thickness),
-			vertex(visual.outer_radius, -visual.base_thickness),
-			vertex(visual.outer_radius, outer_scale * y),
-			vertex(visual.inner_radius, inner_scale * y),
+			inner.with_z(-visual.base_thickness),
+			outer.with_z(-visual.base_thickness),
+			outer,
+			inner,
 		]);
+	}
 
+	for k in 0..sides {
 		let base1 = 4 * k;
 		let base2 = 4 * ((k + 1) % sides);
 		for j1 in 0..4 {