feat: add a few more debug demos

examples3d/debug_thin_cube_on_mesh3.rs

@@ -0,0 +1,59 @@
+use rapier3d::prelude::*;
+use rapier_testbed3d::Testbed;
+
+// This shows a bug when a cylinder is in contact with a very large
+// but very thin cuboid. In this case the EPA returns an incorrect
+// contact normal, resulting in the cylinder falling through the floor.
+pub fn init_world(testbed: &mut Testbed) {
+    /*
+     * World
+     */
+    let mut bodies = RigidBodySet::new();
+    let mut colliders = ColliderSet::new();
+    let impulse_joints = ImpulseJointSet::new();
+    let multibody_joints = MultibodyJointSet::new();
+
+    /*
+     * Ground
+     */
+    let ground_size = 100.1;
+    let ground_height = 0.1;
+
+    // let vertices = vec![
+    //     point![-50.0, 0.0, -50.0],
+    //     point![-50.0, 0.0, 50.0],
+    //     point![50.0, 0.0, 50.0],
+    //     point![50.0, 0.0, -50.0],
+    // ];
+    // let indices = vec![[0, 1, 2], [0, 2, 3]];
+    //
+    // let collider = ColliderBuilder::trimesh_with_flags(vertices, indices, TriMeshFlags::all());
+    // colliders.insert(collider);
+
+    let heights = DMatrix::repeat(2, 2, 0.0);
+    let collider = ColliderBuilder::heightfield_with_flags(
+        heights,
+        Vector::new(50.0, 1.0, 50.0),
+        HeightFieldFlags::FIX_INTERNAL_EDGES,
+    );
+    colliders.insert(collider);
+
+    /*
+     * Create the cubes
+     */
+    // Build the rigid body.
+    let rigid_body = RigidBodyBuilder::dynamic()
+        .translation(vector![0.0, 5.0, 0.0])
+        .rotation(vector![0.5, 0.0, 0.5])
+        .linvel(vector![0.0, -100.0, 0.0])
+        .soft_ccd_enabled(true);
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(0.01, 0.015, 5.0);
+    colliders.insert_with_parent(collider, handle, &mut bodies);
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world(bodies, colliders, impulse_joints, multibody_joints);
+    testbed.look_at(point![100.0, 100.0, 100.0], Point::origin());
+}