Unstitch and Reverse Normal (#856)

Unstitch takes a body's faces out as surface bodies; Reverse Normal turns a surface body's faces over. Both are saved in format 18. Closes #766.

crates/doc/src/assembly.rs

@@ -337,6 +337,7 @@ impl FeatureKind {
             | FeatureKind::MeshConvert { .. }
             | FeatureKind::BodyTransfer { .. } => {}
             FeatureKind::Patch { edges, .. } | FeatureKind::SurfaceExtend { edges, .. } => edges.iter_mut().for_each(pt),
+            FeatureKind::Unstitch { faces, .. } | FeatureKind::ReverseNormal { faces, .. } => faces.iter_mut().for_each(pt),
             FeatureKind::SurfaceTrim { plane, tool, keep, .. } => {
                 map_plane_ref(m, plane);
                 if let Some(t) = tool {

crates/doc/src/clipboard.rs

@@ -321,6 +321,8 @@ impl FeatureKind {
             | K::SheetConvert { body, .. }
             | K::SurfaceExtend { body, .. }
             | K::SurfaceTrim { body, .. }
+            | K::Unstitch { body, .. }
+            | K::ReverseNormal { body, .. }
             | K::MeshConvert { body, .. } => mapped_name(body, bodies),
             _ => {}
         }

crates/doc/src/document.rs

@@ -937,6 +937,19 @@ pub enum FeatureKind {
         curves: Vec<String>,
         extent: Extent,
     },
+    /// A body taken apart: each face at `faces` (every face when empty) its own surface body,
+    /// the faces left one surface body under the body's name. A solid comes apart into surfaces.
+    Unstitch {
+        body: String,
+        #[serde(default, skip_serializing_if = "Vec::is_empty")]
+        faces: Vec<Vec3>,
+    },
+    /// A surface body with the faces at `faces` (every face when empty) turned over.
+    ReverseNormal {
+        body: String,
+        #[serde(default, skip_serializing_if = "Vec::is_empty")]
+        faces: Vec<Vec3>,
+    },
     /// A planar surface body extended outward by `distance` past the edges through `edges`.
     SurfaceExtend {
         body: String,
@@ -1286,6 +1299,8 @@ impl FeatureKind {
             | K::Thicken { .. }
             | K::SurfaceExtend { .. }
             | K::SurfaceTrim { .. }
+            | K::Unstitch { .. }
+            | K::ReverseNormal { .. }
             | K::Move { .. }
             | K::Import { .. }
             | K::MeshImport { .. }
@@ -1374,6 +1389,8 @@ impl FeatureKind {
             FeatureKind::Thicken { .. } => "ThickenFeature",
             FeatureKind::SurfaceTrim { .. } => "TrimFeature",
             FeatureKind::SurfaceExtend { .. } => "ExtendFeature",
+            FeatureKind::Unstitch { .. } => "UnstitchFeature",
+            FeatureKind::ReverseNormal { .. } => "ReverseNormalFeature",
             FeatureKind::Import { .. } => "BaseFeature",
             FeatureKind::MeshImport { .. } => "MeshFeature",
             FeatureKind::MeshConvert { .. } => "MeshConvertFeature",
@@ -1441,6 +1458,8 @@ impl FeatureKind {
             FeatureKind::Thicken { .. } => "Thicken",
             FeatureKind::SurfaceTrim { .. } => "Trim",
             FeatureKind::SurfaceExtend { .. } => "Extend",
+            FeatureKind::Unstitch { .. } => "Unstitch",
+            FeatureKind::ReverseNormal { .. } => "ReverseNormal",
             FeatureKind::Import { .. } => "Import",
             FeatureKind::MeshImport { .. } => "Mesh",
             FeatureKind::MeshConvert { .. } => "ConvertMesh",
@@ -1669,6 +1688,7 @@ impl FeatureKind {
             FeatureKind::Thicken { thickness, .. } => v.push(thickness),
             FeatureKind::SurfaceTrim { plane, .. } => plane_exprs(plane, &mut v),
             FeatureKind::SurfaceExtend { distance, .. } => v.push(distance),
+            FeatureKind::Unstitch { .. } | FeatureKind::ReverseNormal { .. } => {}
             FeatureKind::Patch { .. } => {}
             FeatureKind::Import { .. } | FeatureKind::MeshImport { .. } | FeatureKind::BodyTransfer { .. } => {}
         }

crates/doc/src/eval.rs

@@ -3543,7 +3543,9 @@ fn eval_feature(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature, st:
         | FeatureKind::Thicken { .. }
         | FeatureKind::SurfaceTrim { .. }
         | FeatureKind::SurfaceExtend { .. }
-        | FeatureKind::SurfaceExtrude { .. } => surface::eval(doc, vals, f, st),
+        | FeatureKind::SurfaceExtrude { .. }
+        | FeatureKind::Unstitch { .. }
+        | FeatureKind::ReverseNormal { .. } => surface::eval(doc, vals, f, st),
         FeatureKind::Emboss { .. }
         | FeatureKind::Rib { .. }
         | FeatureKind::ReplaceFace { .. }

crates/doc/src/eval_surface.rs

@@ -1,5 +1,5 @@
-//! Evaluation of the surface features: Patch, Stitch, Thicken, Trim, Extend and Surface Extrude
-//! (kernel `surfaces`).
+//! Evaluation of the surface features: Patch, Stitch, Thicken, Trim, Extend, Surface Extrude,
+//! Unstitch and Reverse Normal (kernel `surfaces`).
 
 use super::*;
 use solidcraft_geom::Seg2;
@@ -113,6 +113,37 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             st.bodies.push(ModelBody::new(name, body, f.id));
             Ok(())
         }
+        FeatureKind::Unstitch { body, faces } => {
+            let i = st.bodies.iter().position(|b| &b.name == body).ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
+            let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
+            let (pieces, rest) = kernel::unstitch(&mb.body, faces)?;
+            let source = mb.traced();
+            // The faces left keep the body's name; each face taken out is a new surface body.
+            match rest {
+                Some(rest) => {
+                    if let Some(slot) = st.bodies.get_mut(i) {
+                        *slot = ModelBody::traced_new(mb.name.clone(), source.then(rest), mb.feature);
+                    }
+                }
+                None => {
+                    st.bodies.remove(i);
+                }
+            }
+            for (k, piece) in pieces.into_iter().enumerate() {
+                let name = new_name(st, f, k);
+                st.bodies.push(ModelBody::traced_new(name, source.then(piece), f.id));
+            }
+            Ok(())
+        }
+        FeatureKind::ReverseNormal { body, faces } => {
+            let i = st.bodies.iter().position(|b| &b.name == body).ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
+            let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
+            let turned = mb.traced().then(kernel::reverse_faces(&mb.body, faces)?);
+            if let Some(slot) = st.bodies.get_mut(i) {
+                *slot = ModelBody::traced_new(mb.name, turned, mb.feature);
+            }
+            Ok(())
+        }
         _ => Err(DocError::Invalid("not a surface feature".into())),
     }
 }

crates/doc/src/format.rs

@@ -104,13 +104,17 @@
 //!   Construction Geometries); a sketch that shows its construction geometry saves as before.
 //!   A `SurfaceExtrude` feature (Surface Extrude: `sketch`, optional `profiles`, `curves` and
 //!   `extent`, walls only) is first saved in 17; 0.8.0 would refuse the unknown feature.
+//! - 18: surface features 0.9.0 doesn't know: `Unstitch` (a body's faces taken out as surface
+//!   bodies) and `ReverseNormal` (a surface body's faces turned over), each a `body` and
+//!   optional `faces` points. Version 17 designs need no transformation; the version stamp makes
+//!   0.9.0 (which reads up to 17) ask for an update instead of meeting a feature it can't read.
 
 use serde_json::Value;
 
 use crate::{DocError, Document, Result};
 
 /// The format this build writes.
-pub const FORMAT: u32 = 17;
+pub const FORMAT: u32 = 18;
 
 pub fn format_string(n: u32) -> String {
     format!("solidcraft/{n}")
@@ -127,7 +131,7 @@ pub fn version_of(s: &str) -> Option<u32> {
 
 /// JSON-level upgrades: entry `i` turns format `i + 1` into `i + 2`.
 type JsonStep = fn(&mut Value) -> Result<()>;
-const JSON_STEPS: [JsonStep; 16] = [
+const JSON_STEPS: [JsonStep; 17] = [
     |_| Ok(()),
     v2_to_v3,
     v3_to_v4,
@@ -144,6 +148,7 @@ const JSON_STEPS: [JsonStep; 16] = [
     |_| Ok(()),
     |_| Ok(()),
     |_| Ok(()),
+    |_| Ok(()),
 ];
 
 /// Stored face and edge names were worked out from geometry before format 14; they get the

crates/doc/src/params.rs

@@ -277,6 +277,7 @@ impl FeatureKind {
             FeatureKind::Thicken { thickness, .. } => v.push(("Thickness", thickness, L)),
             FeatureKind::SurfaceTrim { plane, .. } => plane_inputs_mut(plane, &mut v),
             FeatureKind::SurfaceExtend { distance, .. } => v.push(("Distance", distance, L)),
+            FeatureKind::Unstitch { .. } | FeatureKind::ReverseNormal { .. } => {}
             FeatureKind::Patch { .. } => {}
             FeatureKind::Combine { .. }
             | FeatureKind::SheetBase { .. }