Curvature-continuous (G2) fillets for straight planar edges (#862)

Fillet gets a Curvature (G2) radius type (type: "curvature", alias "g2"): a quintic blend whose size is the equivalent circular setback, for convex and concave straight edges between planar faces with a perpendicular planar end face at each end. Unsupported cases are refused rather than falling back to a circular fillet, and a blend that would cross a loop in its end face is refused. Persisted as a fillet style under format 19; labels in en/de/ja/ko/zh.

Co-authored-by: midasdf <midasdf@users.noreply.github.com>

crates/engine/src/cmd/edit.rs

@@ -821,7 +821,7 @@ fn input_keys(kind: &FeatureKind) -> Vec<(String, solidcraft_doc::expr::Kind)> {
                     *key = format!("fillet.control.{i}");
                 }
             }
-            solidcraft_doc::FilletStyle::Constant | solidcraft_doc::FilletStyle::Chord => {}
+            solidcraft_doc::FilletStyle::Constant | solidcraft_doc::FilletStyle::Chord | solidcraft_doc::FilletStyle::Curvature => {}
         }
     }
     keys

crates/engine/src/cmd/edit_tests.rs

@@ -8,6 +8,28 @@ fn run(s: &mut Session, id: &str, params: Value) -> Value {
     s.execute(id, &params).unwrap_or_else(|e| panic!("{id} {params}: {e}"))
 }
 
+#[test]
+fn g2_fillet_survives_edit_undo_and_reopen() {
+    use solidcraft_doc::{Document, FeatureKind, FilletStyle};
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 20, "width": 20, "height": 20, "name": "Base"}));
+    run(&mut s, "solid.fillet", json!({"edges": [[20, 0, 10]], "radius": 2, "type": "g2", "name": "Smooth"}));
+    assert!(matches!(&s.doc.find_feature("Smooth").unwrap().kind, FeatureKind::Fillet { style: FilletStyle::Curvature, .. }));
+    let before = run(&mut s, "inspect.measure", json!({}))["total"]["volume_mm3"].as_f64().unwrap();
+    run(&mut s, "timeline.edit", json!({"feature": "Smooth", "set": {"radius": "3"}}));
+    let after = run(&mut s, "inspect.measure", json!({}))["total"]["volume_mm3"].as_f64().unwrap();
+    assert!(after < before);
+    run(&mut s, "edit.undo", json!({}));
+    let undo = run(&mut s, "inspect.measure", json!({}))["total"]["volume_mm3"].as_f64().unwrap();
+    assert!((undo - before).abs() < 1e-6);
+    run(&mut s, "edit.redo", json!({}));
+    let mut reopened = Session::new(Document::from_json(&s.doc.to_json()).unwrap());
+    assert!(matches!(&reopened.doc.find_feature("Smooth").unwrap().kind, FeatureKind::Fillet { style: FilletStyle::Curvature, .. }));
+    let volume = run(&mut reopened, "inspect.measure", json!({}))["total"]["volume_mm3"].as_f64().unwrap();
+    assert!((volume - after).abs() < 1e-6);
+    assert!(s.execute("solid.fillet", &json!({"edges": [[0, 0, 10]], "radius": 2, "type": "curvature", "fit": "reduce"})).is_err());
+}
+
 #[test]
 fn redefining_a_blend_replaces_persistent_edge_selection_and_survives_resize() {
     let mut s = Session::default();

crates/engine/src/cmd/features.rs

@@ -31,7 +31,7 @@ pub static COMMANDS: &[CommandSpec] = &[
         .at("SOLID", "MODIFY")
         .icon("fillet")
         .key("F")
-        .params("edges: [[x,y,z] point on edge | {body, index}]; radius: expr; body?; type?: constant|chord (radius is the width across)|variable (radius at the end nearest start, radius2 at the other; one end may be 0, where the round closes to the corner)|spline (the radius along the edge is a clamped B-spline from the end nearest start: radius is its first control radius, radii the rest, knots its knot vector from 0 to 1; one end may be 0); radius2?; start?: [x,y,z]; radii?: [expr, …]; knots?: [number, …]; mid?: [[position 0…1 from start, radius expr], …] (variable radii between the ends); smooth?: bool (smooth instead of straight between the radii); fit?: exact|reduce|taper (exact, the default: a radius too large for the geometry around the edges is refused; reduce: where it doesn't fit it is reduced to the largest that does, one radius for edges sharing a face; the smallest used is returned as `radius_applied`, each edge's as `radii_applied: [{edge: [x,y,z], radius}]`, and noted in the feature's warning; taper: along each straight edge between planar faces where it doesn't fit, the radius follows the room there as a smooth spline, down to 0 where a face closes to a point, noted in the feature's warning)"),
+        .params("edges: [[x,y,z] point on edge | {body, index}]; radius: expr; body?; type?: constant|curvature (alias g2: curvature-continuous quintic between planar faces along straight edges, one perpendicular planar end face at each end; radius sets the equivalent circular setback, not constant curvature; exact fit only)|chord (radius is the width across)|variable (radius at the end nearest start, radius2 at the other; one end may be 0, where the round closes to the corner)|spline (the radius along the edge is a clamped B-spline from the end nearest start: radius is its first control radius, radii the rest, knots its knot vector from 0 to 1; one end may be 0); radius2?; start?: [x,y,z]; radii?: [expr, …]; knots?: [number, …]; mid?: [[position 0…1 from start, radius expr], …] (variable radii between the ends); smooth?: bool (smooth instead of straight between the radii); fit?: exact|reduce|taper (exact, the default: a radius too large for the geometry around the edges is refused; reduce: where it doesn't fit it is reduced to the largest that does, one radius for edges sharing a face; the smallest used is returned as `radius_applied`, each edge's as `radii_applied: [{edge: [x,y,z], radius}]`, and noted in the feature's warning; taper: along each straight edge between planar faces where it doesn't fit, the radius follows the room there as a smooth spline, down to 0 where a face closes to a point, noted in the feature's warning)"),
     CommandSpec::new("solid.chamfer", "Chamfer", chamfer).at("SOLID", "MODIFY").icon("chamfer").params("edges: [[x,y,z] | {body, index}]; distance: expr; distance2?: expr (along the second face) | angle?: expr (from the first face); flip?: bool (which face is first: by default the one facing up most); body?"),
     CommandSpec::new("solid.combine", "Combine", combine).at("SOLID", "MODIFY").icon("combine").params("target: body; tools: [body]; operation?: join|cut|intersect; keep_tools?: bool; new_component?: bool (the result goes into a new component; component_name?)"),
     CommandSpec::new("solid.pattern.rectangular", "Rectangular Pattern", pattern_rect)
@@ -857,6 +857,7 @@ fn fillet(s: &mut Session, p: &Value) -> Result<Value> {
     let style = match str_(p, "type").map(str::to_ascii_lowercase).as_deref() {
         None | Some("constant") | Some("rolling_ball") => solidcraft_doc::FilletStyle::Constant,
         Some("chord") | Some("chord_length") => solidcraft_doc::FilletStyle::Chord,
+        Some("curvature") | Some("g2") => solidcraft_doc::FilletStyle::Curvature,
         Some("variable") => {
             let radius2 = req_expr(cmd, p, "radius2")?;
             check_expr(s, &radius2, Kind::Length, cmd, "radius2")?;
@@ -906,7 +907,7 @@ fn fillet(s: &mut Session, p: &Value) -> Result<Value> {
             }
             solidcraft_doc::FilletStyle::Spline { start, knots, radii }
         }
-        Some(o) => return Err(bad(cmd, format!("unknown fillet type `{o}` (constant, chord, variable or spline)"))),
+        Some(o) => return Err(bad(cmd, format!("unknown fillet type `{o}` (constant, chord, variable, spline or curvature)"))),
     };
     let fit = match str_(p, "fit").map(str::to_ascii_lowercase).as_deref() {
         None | Some("exact") => solidcraft_doc::FilletFit::Exact,