fix: draft a whole round wall from one pick (#547) (#603)

Draft extends the picked faces to every face on the same surface, so one pick on a cylinder's side (stored as two halves) drafts the whole round wall into a frustum. Un-ignores the #547 regression test and adds a kernel test for a round hole. Fixes #547.

Co-authored-by: jonaswre <[email protected]>

crates/engine/src/tests.rs

@@ -2955,7 +2955,6 @@ fn feature_replies_list_only_the_bodies_they_created() {
 /// Drafting a cylinder's side face 5° from the base plane makes a cone frustum (#547): radius 10
 /// at the base, 10 − 20 · tan 5° at the top.
 #[test]
-#[ignore = "fails until #547 is fixed"]
 fn draft_on_a_cylinder_side_makes_a_frustum() {
     let mut s = Session::default();
     run(&mut s, "solid.cylinder", json!({"radius": 10, "height": 20}));

crates/kernel/src/polyhedron.rs

@@ -306,6 +306,8 @@ fn draft_walls(b: &Body, at: &[Vec3], neutral: &Plane, pull: Vec3, angle: f64) -
             _ => return Err(KernelError::Invalid(format!("no face at {:?}", [p.x, p.y, p.z]))),
         }
     }
+    // A round wall is stored in pieces (a cylinder's two halves): picking one drafts the whole wall.
+    let chosen = crate::offset::with_same_surface(&healed, &chosen);
     Ok(record::after(crate::offset::draft_walls(&healed, &chosen, neutral, pull, angle)?, &healed, &record::counts(&[b])))
 }
 

crates/kernel/src/tests.rs

@@ -1536,6 +1536,21 @@ fn draft_of_a_round_ended_pocket() {
     assert!(rel(v, 80.0 * 60.0 * 25.0 - pocket) < 1e-4, "{v} vs {}", 80.0 * 60.0 * 25.0 - pocket);
 }
 
+/// A round wall is stored in pieces (a cylinder's two halves); one pick drafts all of it (#547).
+/// A hole drafted from the top narrows going down: a frustum from R 10 to 10 − 25 · tan 5°.
+#[test]
+fn draft_of_a_round_hole_from_one_pick() {
+    let block = box_solid(Vec3::ZERO, Vec3::new(60.0, 60.0, 25.0)).unwrap();
+    let hole = cylinder(Vec3::new(30.0, 30.0, -1.0), Vec3::Z, 10.0, 27.0).unwrap();
+    let b = boolean(&block, &hole, BoolOp::Cut).unwrap().unwrap();
+    let a = 5f64.to_radians();
+    let d = draft(&b, &[Vec3::new(40.0, 30.0, 12.5)], &Plane::XY.offset(25.0), Vec3::Z, a).unwrap();
+    let (big, small) = (10.0, 10.0 - 25.0 * a.tan());
+    let want = 60.0 * 60.0 * 25.0 - PI * 25.0 / 3.0 * (big * big + big * small + small * small);
+    let m = measure(&d).unwrap();
+    assert!(rel(m.volume, want) < 1e-4, "{} vs {want}", m.volume);
+}
+
 #[test]
 fn rounded_corners_rounded_again_make_spheres() {
     // Vertical edges first, then the top and bottom loops with the same radius: the corners