Perpendicular Plane (construct.plane.perpendicular {plane, line}): the plane through a straight edge, sketch line or axis, square to a plane or planar face; a line square to the plane is refused (no single answer)

Fixes #20

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01RjGw4gA5ZvKrU8MQP6sBgT

crates/engine/src/cmd/construct.rs

@@ -83,6 +83,9 @@ pub static COMMANDS: &[CommandSpec] = &[
         .at("SOLID", "CONSTRUCT")
         .icon("plane")
         .params("path: edge or sketch curve ref; t: expr, 0…1 along it (default 0.5); name? The plane is square to the path there"),
+    CommandSpec::new("construct.plane.perpendicular", "Perpendicular Plane", plane_perpendicular).at("SOLID", "CONSTRUCT").icon("plane").params(
+        "plane: plane or planar face ref; line: straight edge, sketch line or axis ref; name? The plane holds the line and is square to the plane",
+    ),
 ];
 
 /// A reference from its JSON form.
@@ -249,3 +252,9 @@ fn plane_along(s: &mut Session, p: &Value) -> Result<Value> {
     let t = t_param(s, p, cmd)?;
     plane(s, p, PlaneRef::AlongPath { path: Box::new(path), t })
 }
+
+fn plane_perpendicular(s: &mut Session, p: &Value) -> Result<Value> {
+    let cmd = "construct.plane.perpendicular";
+    let (base, line) = (geo(s, p.get("plane"), cmd, "plane")?, geo(s, p.get("line"), cmd, "line")?);
+    plane(s, p, PlaneRef::Perpendicular { plane: Box::new(base), line: Box::new(line) })
+}

crates/engine/src/construct_tests.rs

@@ -257,3 +257,18 @@ fn construction_lives_in_the_component_frame() {
     run(&mut s, "occurrence.move", json!({"occurrence": "Part:1", "translate": [0, 20, 0]}));
     assert!(near(point(&s, "PinTop"), Vec3::new(50.0, 20.0, 10.0)), "{:?}", point(&s, "PinTop"));
 }
+
+#[test]
+fn plane_perpendicular_to_a_plane_through_a_line() {
+    let mut s = part();
+    // Through the box's front bottom edge (along X), square to the bottom: the front face's plane.
+    run(&mut s, "construct.plane.perpendicular", json!({"plane": {"face": [20, 15, 0]}, "line": {"edge": [20, 0, 0]}, "name": "F"}));
+    let f = plane(&s, "F");
+    assert!(parallel(f.normal(), Vec3::Y) && on_plane(&f, Vec3::new(7.0, 0.0, 13.0)), "{f:?}");
+    // Through the world Z axis, square to XZ: the YZ plane.
+    run(&mut s, "construct.plane.perpendicular", json!({"plane": "XZ", "line": {"axis": "Z"}, "name": "G"}));
+    let g = plane(&s, "G");
+    assert!(parallel(g.normal(), Vec3::X) && on_plane(&g, Vec3::new(0.0, 5.0, 9.0)), "{g:?}");
+    // A line square to the plane has no single answer.
+    assert!(s.execute("construct.plane.perpendicular", &json!({"plane": "XY", "line": {"axis": "Z"}})).is_err());
+}