Add a simpler to lock the rotation or translation of a dynamic rigid-body.

examples3d/all_examples3.rs

@@ -26,6 +26,7 @@ mod fountain3;
 mod heightfield3;
 mod joints3;
 mod keva3;
+mod locked_rotation3;
 mod platform3;
 mod primitives3;
 mod restitution3;
@@ -78,6 +79,7 @@ pub fn main() {
         ("Domino", domino3::init_world),
         ("Heightfield", heightfield3::init_world),
         ("Joints", joints3::init_world),
+        ("Locked rotations", locked_rotation3::init_world),
         ("Platform", platform3::init_world),
         ("Restitution", restitution3::init_world),
         ("Stacks", stacks3::init_world),

examples3d/locked_rotation3.rs

@@ -0,0 +1,66 @@
+use na::{Point3, Vector3};
+use rapier3d::dynamics::{JointSet, RigidBodyBuilder, RigidBodySet};
+use rapier3d::geometry::{ColliderBuilder, ColliderSet};
+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 joints = JointSet::new();
+
+    /*
+     * The ground
+     */
+    let ground_size = 5.0;
+    let ground_height = 0.1;
+
+    let rigid_body = RigidBodyBuilder::new_static()
+        .translation(0.0, -ground_height, 0.0)
+        .build();
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(ground_size, ground_height, ground_size).build();
+    colliders.insert(collider, handle, &mut bodies);
+
+    /*
+     * A rectangle that only rotates along the `x` axis.
+     */
+    let rigid_body = RigidBodyBuilder::new_dynamic()
+        .translation(0.0, 3.0, 0.0)
+        .lock_translations()
+        .principal_inertia(Vector3::zeros(), Vector3::new(false, true, true))
+        .build();
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(0.2, 0.6, 2.0).build();
+    colliders.insert(collider, handle, &mut bodies);
+
+    /*
+     * A capsule that cannot rotate.
+     * We initialize it in a tilted position to demonstrate the
+     * fact that is cannot rotate.
+     */
+    let rigid_body = RigidBodyBuilder::new_dynamic()
+        .translation(0.0, 5.0, 0.0)
+        .rotation(Vector3::x() * 1.0)
+        .lock_rotations()
+        .build();
+    let handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::capsule_y(0.6, 0.4).build();
+    colliders.insert(collider, handle, &mut bodies);
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world(bodies, colliders, joints);
+    testbed.look_at(Point3::new(10.0, 3.0, 0.0), Point3::new(0.0, 3.0, 0.0));
+}
+
+fn main() {
+    let testbed = Testbed::from_builders(0, vec![("Boxes", init_world)]);
+    testbed.run()
+}