fix(modify): preserve polyline extrusion frames

src/modules/draw/modify/explode.rs

@@ -153,6 +153,11 @@ fn explode_polyline2d(p: &Polyline2D) -> Vec<EntityType> {
     let closed = p.is_closed();
     let n_segs = if closed { n } else { n - 1 };
     let elevation = p.elevation;
+    let normal = DVec3::new(p.normal.x, p.normal.y, p.normal.z)
+        .try_normalize()
+        .unwrap_or(DVec3::Z);
+    let normal = Vector3::new(normal.x, normal.y, normal.z);
+    let plane = crate::entities::curve::ocs_plane(normal.clone(), elevation);
 
     let mut result = Vec::new();
     for i in 0..n_segs {
@@ -164,15 +169,25 @@ fn explode_polyline2d(p: &Polyline2D) -> Vec<EntityType> {
         if v0.bulge.abs() < 1e-10 {
             let mut common = p.common.clone();
             common.handle = Handle::NULL;
+            let start = plane.point_at(p0);
+            let end = plane.point_at(p1);
             result.push(EntityType::Line(LineEnt {
                 common,
-                start: Vector3::new(p0[0], p0[1], elevation),
-                end: Vector3::new(p1[0], p1[1], elevation),
+                start: Vector3::new(start[0], start[1], start[2]),
+                end: Vector3::new(end[0], end[1], end[2]),
                 thickness: p.thickness,
+                normal: normal.clone(),
                 ..LineEnt::new()
             }));
-        } else if let Some(arc) = bulge_to_arc(p0, p1, v0.bulge, elevation, &p.common, p.thickness)
-        {
+        } else if let Some(arc) = bulge_to_arc(
+            p0,
+            p1,
+            v0.bulge,
+            elevation,
+            &p.common,
+            p.thickness,
+            normal.clone(),
+        ) {
             result.push(arc);
         }
     }
@@ -240,12 +255,21 @@ fn explode_lwpolyline(p: &LwPolyline) -> Vec<EntityType> {
                 start: Vector3::new(p0[0], p0[1], elevation),
                 end: Vector3::new(p1[0], p1[1], elevation),
                 thickness: p.thickness,
+                normal: p.normal.clone(),
                 ..LineEnt::new()
             };
             result.push(EntityType::Line(line));
         } else {
             // Arc segment from bulge
-            if let Some(arc) = bulge_to_arc(p0, p1, v0.bulge, elevation, &p.common, p.thickness) {
+            if let Some(arc) = bulge_to_arc(
+                p0,
+                p1,
+                v0.bulge,
+                elevation,
+                &p.common,
+                p.thickness,
+                p.normal.clone(),
+            ) {
                 result.push(arc);
             }
         }
@@ -262,6 +286,7 @@ fn bulge_to_arc(
     elevation: f64,
     common_src: &EntityCommon,
     thickness: f64,
+    normal: Vector3,
 ) -> Option<EntityType> {
     let ba = crate::entities::common::BulgeArc::from_bulge(p0, p1, bulge)?;
 
@@ -285,6 +310,7 @@ fn bulge_to_arc(
         start_angle,
         end_angle,
         thickness,
+        normal,
         ..ArcEnt::new()
     };
     Some(EntityType::Arc(arc))
@@ -1763,4 +1789,28 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    fn explode_keeps_polyline2d_extrusion() {
+        use acadrust::entities::Vertex2D;
+
+        let mut pl = Polyline2D::new();
+        pl.vertices = vec![
+            Vertex2D::new(Vector3::new(0.0, 0.0, 0.0)),
+            Vertex2D::new(Vector3::new(10.0, 0.0, 0.0)),
+        ];
+        pl.elevation = 2.0;
+        pl.thickness = -4.0;
+        pl.normal = Vector3::new(1.0, 0.0, 0.0);
+
+        let pieces = explode_polyline_segments(&EntityType::Polyline2D(pl));
+        let Some(EntityType::Line(line)) = pieces.first() else {
+            panic!("expected one line");
+        };
+        assert_eq!(pieces.len(), 1);
+        assert_eq!(line.normal, Vector3::new(1.0, 0.0, 0.0));
+        assert!((line.thickness + 4.0).abs() < 1e-12);
+        assert!((line.start.x - 2.0).abs() < 1e-12);
+        assert!((line.end.x - 2.0).abs() < 1e-12);
+    }
 }