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use crate::geometry::PolyhedronFace;
use crate::geometry::{cuboid, Cuboid, Cylinder, Triangle};
use crate::math::{Point, Vector};
use approx::AbsDiffEq;
use na::{Unit, Vector2, Vector3};
use ncollide::shape::Segment;
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<f32> {
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];
}
}
}
}
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