Split Body: a sketch line as the splitting tool (#1552) (#1592)

Thanks @DuBearte.

crates/engine/src/cmd/features.rs

@@ -105,7 +105,7 @@ pub static COMMANDS: &[CommandSpec] = &[
     CommandSpec::new("solid.split_body", "Split Body", split_body)
         .at("SOLID", "MODIFY")
         .icon("split")
-        .params("body: name; plane: XY|XZ|YZ|plane name|{origin, normal} — or tool: {body, point} (a face of a body, its surface extended)"),
+        .params("body: name; plane: XY|XZ|YZ|plane name|{origin, normal} — or tool: {body, point} (a face of a body, its surface extended) — or sketch: id, line: curve id (a straight sketch line, along the sketch's normal)"),
     CommandSpec::new("solid.press_pull", "Press Pull", press_pull)
         .at("SOLID", "MODIFY")
         .icon("presspull")
@@ -1472,6 +1472,27 @@ fn split_body(s: &mut Session, p: &Value) -> Result<Value> {
     if s.model.state().body(&body).is_none() {
         return Err(bad(cmd, format!("no body `{body}`")));
     }
+    // A straight sketch line as the tool: `sketch` and `line` (#1552).
+    if p.get("sketch").is_some_and(|v| !v.is_null()) || p.get("line").is_some_and(|v| !v.is_null()) {
+        let sketch = p.get("sketch").and_then(Value::as_u64).ok_or_else(|| bad(cmd, "`sketch` must be a sketch feature id"))?;
+        let line = str_(p, "line").ok_or_else(|| bad(cmd, "`line` must name a line of the sketch"))?.to_string();
+        let st = s.model.state();
+        if st.sketch(sketch).is_none() {
+            return Err(bad(cmd, format!("no sketch {sketch}")));
+        }
+        solidcraft_doc::sketch_line_plane(&st, sketch, &line).map_err(|e| bad(cmd, e.to_string()))?;
+        return add_feature(
+            s,
+            p,
+            FeatureKind::Split {
+                body: BodyName(body),
+                plane: solidcraft_doc::PlaneRef::Origin { name: "XY".into() },
+                tool: None,
+                sketch: Some(solidcraft_doc::SketchId(sketch)),
+                line: Some(line),
+            },
+        );
+    }
     // A face as the tool: `tool: {body, point}` (its surface extended); else a plane.
     if let Some(t) = p.get("tool").filter(|t| !t.is_null()) {
         let tb = t.get("body").and_then(Value::as_str).ok_or_else(|| bad(cmd, "`tool.body` must name a body"))?.to_string();
@@ -1488,11 +1509,13 @@ fn split_body(s: &mut Session, p: &Value) -> Result<Value> {
                 body: BodyName(body),
                 plane: solidcraft_doc::PlaneRef::Origin { name: "XY".into() },
                 tool: Some(solidcraft_doc::FaceAt { body: BodyName(tb), point: Position(point) }),
+                sketch: None,
+                line: None,
             },
         );
     }
     let plane = plane_param(s, p.get("plane"), cmd)?;
-    add_feature(s, p, FeatureKind::Split { body: BodyName(body), plane, tool: None })
+    add_feature(s, p, FeatureKind::Split { body: BodyName(body), plane, tool: None, sketch: None, line: None })
 }
 
 /// ISO 273 clearance hole diameters (close, normal, loose fit) for metric bolts.

crates/engine/src/tests.rs

@@ -1804,6 +1804,47 @@ fn split_body_by_a_face() {
     assert!(s.execute("solid.split_body", &json!({"body": "Block", "tool": {"body": "Tool", "point": [100, 0, 0]}})).is_err());
 }
 
+/// Split Body by a sketch line (#1552): the plane through the line along the sketch's normal
+/// splits a box; the split follows the line when the sketch changes, the design saves the line,
+/// and anything but a straight line of a sketch is refused.
+#[test]
+fn split_body_by_a_sketch_line() {
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 10, "width": 20, "height": 30, "body_name": "Block"}));
+    let sk = run(&mut s, "sketch.create", json!({"plane": "XY"}))["sketch"].as_u64().unwrap();
+    run(&mut s, "sketch.line", json!({"points": [[4, -5], [4, 25]], "ids": ["cut"]}));
+    run(&mut s, "sketch.circle.center", json!({"center": [50, 50], "radius": 2, "id": "c"}));
+    run(&mut s, "sketch.finish", json!({}));
+    let volumes = |s: &Session| {
+        let st = s.world_state();
+        let mut v: Vec<f64> =
+            st.bodies.iter().filter(|b| b.name.starts_with("Block")).map(|b| solidcraft_kernel::measure(&b.body).unwrap().volume).collect();
+        v.sort_by(f64::total_cmp);
+        v
+    };
+    for bad in [
+        json!({"body": "Block", "sketch": sk, "line": "c"}),
+        json!({"body": "Block", "sketch": sk}),
+        json!({"body": "Block", "sketch": 999, "line": "cut"}),
+    ] {
+        assert!(s.execute("solid.split_body", &bad).is_err(), "{bad}");
+    }
+    run(&mut s, "solid.split_body", json!({"body": "Block", "sketch": sk, "line": "cut"}));
+    let v = volumes(&s);
+    assert!(v.len() == 2 && rel(v[0], 2400.0) < 1e-6 && rel(v[1], 3600.0) < 1e-6, "{v:?}");
+    // The split follows the line.
+    run(&mut s, "sketch.edit", json!({"sketch": sk}));
+    run(&mut s, "sketch.move_point", json!({"point": "cut.start", "to": [2, -5]}));
+    run(&mut s, "sketch.move_point", json!({"point": "cut.end", "to": [2, 25]}));
+    run(&mut s, "sketch.finish", json!({}));
+    let v = volumes(&s);
+    assert!(v.len() == 2 && rel(v[0], 1200.0) < 1e-6 && rel(v[1], 4800.0) < 1e-6, "{v:?}");
+    // The design keeps the sketch and the line.
+    let saved: Value = serde_json::from_str(&s.doc.to_json()).unwrap();
+    let split = saved["features"].as_array().and_then(|f| f.iter().find(|f| f["type"] == "split")).cloned().unwrap();
+    assert_eq!((split["sketch"].as_u64(), split["line"].as_str()), (Some(sk), Some("cut")), "{split}");
+}
+
 /// Fillet types: chord length (radius from the face angle) and a radius varying along the
 /// edge; volumes from the removed material.
 #[test]