Merge pull request #41 from dimforge/cylinder

Add cylinder and cone support + use a trait-object for shapes.

1 files changed, 132 insertions, 0 deletions

diff --git a/src/geometry/polygonal_feature_map.rs b/src/geometry/polygonal_feature_map.rs
new file mode 100644
index 0000000..2a8fc8d
--- /dev/null
+++ b/src/geometry/polygonal_feature_map.rs
@@ -0,0 +1,132 @@
+use crate::geometry::PolyhedronFace;
+use crate::geometry::{cuboid, Cone, Cuboid, Cylinder, Segment, Triangle};
+use crate::math::{Point, Vector};
+use approx::AbsDiffEq;
+use na::{Unit, Vector2};
+use ncollide::shape::SupportMap;
+
+/// Trait implemented by convex shapes with features with polyhedral approximations.
+pub trait PolygonalFeatureMap: SupportMap<f32> {
+    fn local_support_feature(&self, dir: &Unit<Vector<f32>>, out_feature: &mut PolyhedronFace);
+}
+
+impl PolygonalFeatureMap for Segment {
+    fn local_support_feature(&self, _: &Unit<Vector<f32>>, out_feature: &mut PolyhedronFace) {
+        *out_feature = PolyhedronFace::from(*self);
+    }
+}
+
+impl PolygonalFeatureMap for Triangle {
+    fn local_support_feature(&self, _: &Unit<Vector<f32>>, out_feature: &mut PolyhedronFace) {
+        *out_feature = PolyhedronFace::from(*self);
+    }
+}
+
+impl PolygonalFeatureMap for Cuboid {
+    fn local_support_feature(&self, dir: &Unit<Vector<f32>>, out_feature: &mut PolyhedronFace) {
+        let face = cuboid::support_face(self, **dir);
+        *out_feature = PolyhedronFace::from(face);
+    }
+}
+
+impl PolygonalFeatureMap for Cylinder {
+    fn local_support_feature(&self, dir: &Unit<Vector<f32>>, out_features: &mut PolyhedronFace) {
+        // About feature ids.
+        // At all times, we consider our cylinder to be approximated as follows:
+        // - The curved part is approximated by a single segment.
+        // - Each flat cap of the cylinder is approximated by a square.
+        // - The curved-part segment has a feature ID of 0, and its endpoint with negative
+        //   `y` coordinate has an ID of 1.
+        // - The bottom cap has its vertices with feature ID of 1,3,5,7 (in counter-clockwise order
+        //   when looking at the cap with an eye looking towards +y).
+        // - The bottom cap has its four edge feature IDs of 2,4,6,8, in counter-clockwise order.
+        // - The bottom cap has its face feature ID of 9.
+        // - The feature IDs of the top cap are the same as the bottom cap to which we add 10.
+        //   So its vertices have IDs 11,13,15,17, its edges 12,14,16,18, and its face 19.
+        // - Note that at all times, one of each cap's vertices are the same as the curved-part
+        //   segment endpoints.
+        let dir2 = Vector2::new(dir.x, dir.z)
+            .try_normalize(f32::default_epsilon())
+            .unwrap_or(Vector2::x());
+
+        if dir.y.abs() < 0.5 {
+            // We return a segment lying on the cylinder's curved part.
+            out_features.vertices[0] = Point::new(
+                dir2.x * self.radius,
+                -self.half_height,
+                dir2.y * self.radius,
+            );
+            out_features.vertices[1] =
+                Point::new(dir2.x * self.radius, self.half_height, dir2.y * self.radius);
+            out_features.eids = [0, 0, 0, 0];
+            out_features.fid = 0;
+            out_features.num_vertices = 2;
+            out_features.vids = [1, 11, 11, 11];
+        } else {
+            // We return a square approximation of the cylinder cap.
+            let y = self.half_height.copysign(dir.y);
+            out_features.vertices[0] = Point::new(dir2.x * self.radius, y, dir2.y * self.radius);
+            out_features.vertices[1] = Point::new(-dir2.y * self.radius, y, dir2.x * self.radius);
+            out_features.vertices[2] = Point::new(-dir2.x * self.radius, y, -dir2.y * self.radius);
+            out_features.vertices[3] = Point::new(dir2.y * self.radius, y, -dir2.x * self.radius);
+
+            if dir.y < 0.0 {
+                out_features.eids = [2, 4, 6, 8];
+                out_features.fid = 9;
+                out_features.num_vertices = 4;
+                out_features.vids = [1, 3, 5, 7];
+            } else {
+                out_features.eids = [12, 14, 16, 18];
+                out_features.fid = 19;
+                out_features.num_vertices = 4;
+                out_features.vids = [11, 13, 15, 17];
+            }
+        }
+    }
+}
+
+impl PolygonalFeatureMap for Cone {
+    fn local_support_feature(&self, dir: &Unit<Vector<f32>>, out_features: &mut PolyhedronFace) {
+        // About feature ids. It is very similar to the feature ids of cylinders.
+        // At all times, we consider our cone to be approximated as follows:
+        // - The curved part is approximated by a single segment.
+        // - The flat cap of the cone is approximated by a square.
+        // - The curved-part segment has a feature ID of 0, and its endpoint with negative
+        //   `y` coordinate has an ID of 1.
+        // - The bottom cap has its vertices with feature ID of 1,3,5,7 (in counter-clockwise order
+        //   when looking at the cap with an eye looking towards +y).
+        // - The bottom cap has its four edge feature IDs of 2,4,6,8, in counter-clockwise order.
+        // - The bottom cap has its face feature ID of 9.
+        // - Note that at all times, one of the cap's vertices are the same as the curved-part
+        //   segment endpoints.
+        let dir2 = Vector2::new(dir.x, dir.z)
+            .try_normalize(f32::default_epsilon())
+            .unwrap_or(Vector2::x());
+
+        if dir.y > 0.0 {
+            // We return a segment lying on the cone's curved part.
+            out_features.vertices[0] = Point::new(
+                dir2.x * self.radius,
+                -self.half_height,
+                dir2.y * self.radius,
+            );
+            out_features.vertices[1] = Point::new(0.0, self.half_height, 0.0);
+            out_features.eids = [0, 0, 0, 0];
+            out_features.fid = 0;
+            out_features.num_vertices = 2;
+            out_features.vids = [1, 11, 11, 11];
+        } else {
+            // We return a square approximation of the cone cap.
+            let y = -self.half_height;
+            out_features.vertices[0] = Point::new(dir2.x * self.radius, y, dir2.y * self.radius);
+            out_features.vertices[1] = Point::new(-dir2.y * self.radius, y, dir2.x * self.radius);
+            out_features.vertices[2] = Point::new(-dir2.x * self.radius, y, -dir2.y * self.radius);
+            out_features.vertices[3] = Point::new(dir2.y * self.radius, y, -dir2.x * self.radius);
+
+            out_features.eids = [2, 4, 6, 8];
+            out_features.fid = 9;
+            out_features.num_vertices = 4;
+            out_features.vids = [1, 3, 5, 7];
+        }
+    }
+}