Surface Loft: sheets through open or closed sections (#847)

Surface Loft lofts open or closed curve chains, one section per sketch in pick order, into surface bodies. Adds the SurfaceLoft feature (format 18 note), the surface.loft command, a dialog with Edit Feature support, and kernel and engine tests.

Part of #757.

crates/ui-egui/src/dialogs_surface.rs

@@ -1,5 +1,5 @@
-//! Dialogs for the surface tools and face splitting (#19): Surface Extrude, Revolve and Sweep,
-//! Patch, Stitch, Thicken, Extend, Trim and Split Face. Each has a live preview and Edit Feature.
+//! Dialogs for the surface tools and face splitting (#19): Surface Extrude, Revolve, Sweep and
+//! Loft, Patch, Stitch, Thicken, Extend, Trim and Split Face. Each has a live preview and Edit Feature.
 
 use serde_json::{Map, Value, json};
 use solidcraft_engine::Sel;
@@ -26,6 +26,7 @@ pub enum Surf {
         axis: Option<Value>,
     },
     Sweep,
+    Loft,
     Patch,
     Unstitch,
     ReverseNormal,
@@ -53,6 +54,7 @@ impl Surf {
             Surf::Extrude { .. } => "SURFACE EXTRUDE",
             Surf::Revolve { .. } => "SURFACE REVOLVE",
             Surf::Sweep => "SURFACE SWEEP",
+            Surf::Loft => "SURFACE LOFT",
             Surf::Patch => "PATCH",
             Surf::Unstitch => "UNSTITCH",
             Surf::ReverseNormal => "REVERSE NORMAL",
@@ -84,6 +86,7 @@ fn inputs(k: &Surf) -> Vec<SelInput> {
         Surf::Extrude { .. } => vec![SelInput::new("Profiles or curves", PROFILES | CURVES, true)],
         Surf::Revolve { .. } => vec![SelInput::new("Profiles or curves", PROFILES | CURVES, true), SelInput::new("Axis", AXES, false)],
         Surf::Sweep => vec![SelInput::new("Profiles or curves", PROFILES | CURVES, true), SelInput::new("Path", CURVES, true)],
+        Surf::Loft => vec![SelInput::new("Sections (one sketch each)", PROFILES | CURVES, true)],
         Surf::Patch => vec![SelInput::new("Boundary", PROFILES | EDGES, true)],
         Surf::Unstitch => vec![SelInput::new("Body, or faces to take out", BODIES | FACES, true)],
         Surf::ReverseNormal => vec![SelInput::new("Surface, or faces to turn over", BODIES | FACES, true)],
@@ -106,6 +109,7 @@ pub fn start(_app: &SolveApp, id: &str) -> Option<(Kind, Vec<SelInput>)> {
         "surface.extrude" => Surf::Extrude { distance: "10 mm".into(), direction: 0 },
         "surface.revolve" => Surf::Revolve { angle: "360 deg".into(), symmetric: false, axis: None },
         "surface.sweep" => Surf::Sweep,
+        "surface.loft" => Surf::Loft,
         "surface.patch" => Surf::Patch,
         "surface.unstitch" => Surf::Unstitch,
         "surface.reverse_normal" => Surf::ReverseNormal,
@@ -168,7 +172,7 @@ pub fn rows(ui: &mut egui::Ui, k: &mut Surf) -> bool {
             combo(ui, "sx_dir", &EXTRUDE_SIDES.map(|(label, _)| label), direction);
             ui.end_row();
         }
-        Surf::Patch | Surf::Trim | Surf::SplitFace | Surf::Unstitch | Surf::ReverseNormal | Surf::Sweep => {}
+        Surf::Patch | Surf::Trim | Surf::SplitFace | Surf::Unstitch | Surf::ReverseNormal | Surf::Sweep | Surf::Loft => {}
     }
     enter
 }
@@ -281,6 +285,34 @@ pub fn commands(app: &SolveApp, k: &Surf, inputs: &[SelInput], extra: &Map<Strin
             p["path"] = json!(path);
             ("surface.sweep", p)
         }
+        Surf::Loft => {
+            need(0, "the sections, one sketch each")?;
+            // One section per sketch, in the order the sketches were first picked.
+            let st = app.session.world_state();
+            let sketch_of = |x: &Sel| match x {
+                Sel::Profile { sketch, .. } => Some(*sketch),
+                Sel::SketchCurve { id } => st.sketches.iter().rev().find(|ss| ss.sketch.curve_index(id).is_some()).map(|ss| ss.feature),
+                _ => None,
+            };
+            let mut order: Vec<u64> = Vec::new();
+            for x in items(inputs, 0) {
+                let sk = sketch_of(x).ok_or("a picked curve is no longer in a sketch")?;
+                if !order.contains(&sk) {
+                    order.push(sk);
+                }
+            }
+            if order.len() < 2 {
+                return Err("pick sections in two or more sketches".into());
+            }
+            let sections: Vec<Value> = order
+                .iter()
+                .map(|sk| {
+                    let picks: Vec<Sel> = items(inputs, 0).iter().filter(|x| sketch_of(x) == Some(*sk)).cloned().collect();
+                    sheet_picks(app, &picks)
+                })
+                .collect::<Result<_, String>>()?;
+            ("surface.loft", json!({ "sections": sections }))
+        }
         Surf::Patch => {
             need(0, "a boundary (sketch profiles or a loop of edges)")?;
             let profiles: Vec<(u64, usize)> =
@@ -405,6 +437,9 @@ pub fn for_feature(app: &SolveApp, kind: &FeatureKind, frame: &Mat) -> Option<(K
             Surf::Sweep,
             vec![sheet_sels(app, *sketch, profiles.as_ref(), curves), path.iter().map(|id| Sel::SketchCurve { id: id.clone() }).collect()],
         ),
+        FeatureKind::SurfaceLoft { sections } => {
+            (Surf::Loft, vec![sections.iter().flat_map(|sec| sheet_sels(app, sec.sketch, sec.profiles.as_ref(), &sec.curves)).collect()])
+        }
         FeatureKind::SurfaceExtrude { sketch, profiles, curves, extent } => {
             let sels = sheet_sels(app, *sketch, profiles.as_ref(), curves);
             let direction = match extent.direction {