Variable-radius fillets through middle points: radii at positions along the edge, straight or smooth between

kernel::fillet_variable_points(body, edge, start, [(position, radius)...], smooth): the radius law is a B-spline of the edge parameter (straight pieces, or C1 cubic pieces with Catmull-Rom slopes), and since every section's arc is affine in its radius the blend is exactly a rational B-spline (degree 2 across, the law's degree along) with B-spline contact curves on the faces. The largest radius along the edge decides whether the blend fits. Fillet type variable takes mid: [[position, radius expr], ...] and smooth; middle radii are parameters of the feature (Mid radius) and follow user parameters. Tests: straight pieces against (1 - pi/4) L (a^2 + ab + b^2) / 3 per piece, smooth against the integrated law, either end as start, refusals; engine test with a parameter-driven middle radius.

Refs #9

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RjGw4gA5ZvKrU8MQP6sBgT

crates/ui-egui/src/dialogs.rs

@@ -2790,7 +2790,7 @@ pub fn for_feature(app: &SolveApp, id: u64, marker: Option<usize>) -> Option<Dia
                     FilletStyle::Chord => {
                         d.extra.insert("type".into(), json!("chord"));
                     }
-                    FilletStyle::Variable { radius2, start } => {
+                    FilletStyle::Variable { radius2, start, .. } => {
                         d.extra.insert("type".into(), json!("variable"));
                         d.extra.insert("radius2".into(), json!(radius2));
                         // The start was the first edge's last point: ends swapped.