Fix torque generation for the prismatic joint motor

examples3d/debug_prismatic3.rs

@@ -0,0 +1,111 @@
+use na::{Point3, Vector3};
+use rapier3d::dynamics::{JointSet, RigidBodyBuilder, RigidBodySet};
+use rapier3d::geometry::{ColliderBuilder, ColliderSet};
+use rapier_testbed3d::Testbed;
+
+fn prismatic_repro(
+    bodies: &mut RigidBodySet,
+    colliders: &mut ColliderSet,
+    joints: &mut JointSet,
+    box_center: Point3<f32>,
+) {
+    use rapier3d::{dynamics::RigidBodyBuilder, geometry::ColliderBuilder};
+    let box_rb = bodies.insert(
+        RigidBodyBuilder::new_dynamic()
+            .translation(box_center.x, box_center.y, box_center.z)
+            .build(),
+    );
+    colliders.insert(
+        ColliderBuilder::cuboid(1.0, 0.25, 1.0).build(),
+        box_rb,
+        bodies,
+    );
+
+    let wheel_y = -1.0;
+    let wheel_positions = vec![
+        Vector3::new(1.0, wheel_y, -1.0),
+        Vector3::new(-1.0, wheel_y, -1.0),
+        Vector3::new(1.0, wheel_y, 1.0),
+        Vector3::new(-1.0, wheel_y, 1.0),
+    ];
+
+    for pos in wheel_positions {
+        let wheel_pos_in_world = box_center + pos;
+        let wheel_rb = bodies.insert(
+            RigidBodyBuilder::new_dynamic()
+                .translation(
+                    wheel_pos_in_world.x,
+                    wheel_pos_in_world.y,
+                    wheel_pos_in_world.z,
+                )
+                .build(),
+        );
+        colliders.insert(ColliderBuilder::ball(0.5).build(), wheel_rb, bodies);
+
+        let mut prismatic = rapier3d::dynamics::PrismaticJoint::new(
+            Point3::new(pos.x, pos.y, pos.z),
+            Vector3::y_axis(),
+            Vector3::default(),
+            Point3::new(0.0, 0.0, 0.0),
+            Vector3::y_axis(),
+            Vector3::default(),
+        );
+        prismatic.configure_motor_model(rapier3d::dynamics::SpringModel::VelocityBased);
+        let (stiffness, damping) = (0.05, 0.2);
+        prismatic.configure_motor_position(0.0, stiffness, damping);
+
+        joints.insert(bodies, box_rb, wheel_rb, prismatic);
+    }
+
+    // put a small box under one of the wheels
+    let gravel = bodies.insert(
+        RigidBodyBuilder::new_dynamic()
+            .translation(box_center.x + 1.0, box_center.y - 2.4, -1.0)
+            .build(),
+    );
+    colliders.insert(
+        ColliderBuilder::cuboid(0.5, 0.1, 0.5).build(),
+        gravel,
+        bodies,
+    );
+}
+
+pub fn init_world(testbed: &mut Testbed) {
+    /*
+     * World
+     */
+    let mut bodies = RigidBodySet::new();
+    let mut colliders = ColliderSet::new();
+    let mut joints = JointSet::new();
+
+    /*
+     * Ground
+     */
+    let ground_size = 50.0;
+    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);
+
+    prismatic_repro(
+        &mut bodies,
+        &mut colliders,
+        &mut joints,
+        Point3::new(0.0, 5.0, 0.0),
+    );
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world(bodies, colliders, joints);
+    testbed.look_at(Point3::new(10.0, 10.0, 10.0), Point3::origin());
+}
+
+fn main() {
+    let testbed = Testbed::from_builders(0, vec![("Boxes", init_world)]);
+    testbed.run()
+}