Merge pull request #120 from dimforge/contact_modification

Add the ability to modify the contact points seen by the constraints solver

4 files changed, 148 insertions, 5 deletions

diff --git a/examples3d/all_examples3.rs b/examples3d/all_examples3.rs
index 9cbf4c3..8a71665 100644
--- a/examples3d/all_examples3.rs
+++ b/examples3d/all_examples3.rs
@@ -29,6 +29,7 @@ mod heightfield3;
 mod joints3;
 mod keva3;
 mod locked_rotations3;
+mod one_way_platforms3;
 mod platform3;
 mod primitives3;
 mod restitution3;
@@ -83,6 +84,7 @@ pub fn main() {
         ("Heightfield", heightfield3::init_world),
         ("Joints", joints3::init_world),
         ("Locked rotations", locked_rotations3::init_world),
+        ("One-way platforms", one_way_platforms3::init_world),
         ("Platform", platform3::init_world),
         ("Restitution", restitution3::init_world),
         ("Sensor", sensor3::init_world),
diff --git a/examples3d/damping3.rs b/examples3d/damping3.rs
index 8c68d3b..3847ceb 100644
--- a/examples3d/damping3.rs
+++ b/examples3d/damping3.rs
@@ -40,6 +40,6 @@ pub fn init_world(testbed: &mut Testbed) {
     /*
      * Set up the testbed.
      */
-    testbed.set_world_with_gravity(bodies, colliders, joints, Vector3::zeros());
+    testbed.set_world_with_params(bodies, colliders, joints, Vector3::zeros(), ());
     testbed.look_at(Point3::new(2.0, 2.5, 20.0), Point3::new(2.0, 2.5, 0.0));
 }
diff --git a/examples3d/fountain3.rs b/examples3d/fountain3.rs
index 5acc2e8..caaa21b 100644
--- a/examples3d/fountain3.rs
+++ b/examples3d/fountain3.rs
@@ -23,16 +23,14 @@ pub fn init_world(testbed: &mut Testbed) {
     let handle = bodies.insert(rigid_body);
     let collider = ColliderBuilder::cuboid(ground_size, ground_height, ground_size).build();
     colliders.insert(collider, handle, &mut bodies);
-    let mut k = 0;
 
     // Callback that will be executed on the main loop to handle proximities.
-    testbed.add_callback(move |mut window, mut graphics, physics, _, _| {
-        k += 1;
+    testbed.add_callback(move |mut window, mut graphics, physics, _, run_state| {
         let rigid_body = RigidBodyBuilder::new_dynamic()
             .translation(0.0, 10.0, 0.0)
             .build();
         let handle = physics.bodies.insert(rigid_body);
-        let collider = match k % 3 {
+        let collider = match run_state.timestep_id % 3 {
             0 => ColliderBuilder::round_cylinder(rad, rad, rad / 10.0).build(),
             1 => ColliderBuilder::cone(rad, rad).build(),
             _ => ColliderBuilder::cuboid(rad, rad, rad).build(),
diff --git a/examples3d/one_way_platforms3.rs b/examples3d/one_way_platforms3.rs
new file mode 100644
index 0000000..173d03d
--- /dev/null
+++ b/examples3d/one_way_platforms3.rs
@@ -0,0 +1,143 @@
+use na::{Point3, Vector3};
+use rapier3d::dynamics::{JointSet, RigidBodyBuilder, RigidBodySet};
+use rapier3d::geometry::{ColliderBuilder, ColliderHandle, ColliderSet};
+use rapier3d::pipeline::{ContactModificationContext, PhysicsHooks, PhysicsHooksFlags};
+use rapier_testbed3d::Testbed;
+
+struct OneWayPlatformHook {
+    platform1: ColliderHandle,
+    platform2: ColliderHandle,
+}
+
+impl PhysicsHooks for OneWayPlatformHook {
+    fn active_hooks(&self) -> PhysicsHooksFlags {
+        PhysicsHooksFlags::MODIFY_SOLVER_CONTACTS
+    }
+
+    fn modify_solver_contacts(&self, context: &mut ContactModificationContext) {
+        // The allowed normal for the first platform is its local +y axis, and the
+        // allowed normal for the second platform is its local -y axis.
+        //
+        // Now we have to be careful because the `manifold.local_n1` normal points
+        // toward the outside of the shape of `context.co1`. So we need to flip the
+        // allowed normal direction if the platform is in `context.collider_handle2`.
+        //
+        // Therefore:
+        // - If context.collider_handle1 == self.platform1 then the allowed normal is +y.
+        // - If context.collider_handle2 == self.platform1 then the allowed normal is -y.
+        // - If context.collider_handle1 == self.platform2 then its allowed normal +y needs to be flipped to -y.
+        // - If context.collider_handle2 == self.platform2 then the allowed normal -y needs to be flipped to +y.
+        let mut allowed_local_n1 = Vector3::zeros();
+
+        if context.collider_handle1 == self.platform1 {
+            allowed_local_n1 = Vector3::y();
+        } else if context.collider_handle2 == self.platform1 {
+            // Flip the allowed direction.
+            allowed_local_n1 = -Vector3::y();
+        }
+
+        if context.collider_handle1 == self.platform2 {
+            allowed_local_n1 = -Vector3::y();
+        } else if context.collider_handle2 == self.platform2 {
+            // Flip the allowed direction.
+            allowed_local_n1 = -Vector3::y();
+        }
+
+        // Call the helper function that simulates one-way platforms.
+        context.update_as_oneway_platform(&allowed_local_n1, 0.1);
+
+        // Set the surface velocity of the accepted contacts.
+        let tangent_velocity = if context.collider_handle1 == self.platform1
+            || context.collider_handle2 == self.platform2
+        {
+            -12.0
+        } else {
+            12.0
+        };
+
+        for contact in context.solver_contacts.iter_mut() {
+            contact.tangent_velocity.z = tangent_velocity;
+        }
+    }
+}
+
+pub fn init_world(testbed: &mut Testbed) {
+    /*
+     * World
+     */
+    let mut bodies = RigidBodySet::new();
+    let mut colliders = ColliderSet::new();
+    let joints = JointSet::new();
+
+    /*
+     * Ground
+     */
+    let rigid_body = RigidBodyBuilder::new_static().build();
+    let handle = bodies.insert(rigid_body);
+
+    let collider = ColliderBuilder::cuboid(9.0, 0.5, 25.0)
+        .translation(0.0, 2.0, 30.0)
+        .modify_solver_contacts(true)
+        .build();
+    let platform1 = colliders.insert(collider, handle, &mut bodies);
+    let collider = ColliderBuilder::cuboid(9.0, 0.5, 25.0)
+        .translation(0.0, -2.0, -30.0)
+        .modify_solver_contacts(true)
+        .build();
+    let platform2 = colliders.insert(collider, handle, &mut bodies);
+
+    /*
+     * Setup the one-way platform hook.
+     */
+    let physics_hooks = OneWayPlatformHook {
+        platform1,
+        platform2,
+    };
+
+    /*
+     * Spawn cubes at regular intervals and apply a custom gravity
+     * depending on their position.
+     */
+    testbed.add_callback(move |mut window, mut graphics, physics, _, run_state| {
+        if run_state.timestep_id % 50 == 0 && physics.bodies.len() <= 7 {
+            // Spawn a new cube.
+            let collider = ColliderBuilder::cuboid(1.0, 2.0, 1.5).build();
+            let body = RigidBodyBuilder::new_dynamic()
+                .translation(0.0, 6.0, 20.0)
+                .build();
+            let handle = physics.bodies.insert(body);
+            physics
+                .colliders
+                .insert(collider, handle, &mut physics.bodies);
+
+            if let (Some(graphics), Some(window)) = (&mut graphics, &mut window) {
+                graphics.add(window, handle, &physics.bodies, &physics.colliders);
+            }
+        }
+
+        physics.bodies.foreach_active_dynamic_body_mut(|_, body| {
+            if body.position().translation.y > 1.0 {
+                body.set_gravity_scale(1.0, false);
+            } else if body.position().translation.y < -1.0 {
+                body.set_gravity_scale(-1.0, false);
+            }
+        });
+    });
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world_with_params(
+        bodies,
+        colliders,
+        joints,
+        Vector3::new(0.0, -9.81, 0.0),
+        physics_hooks,
+    );
+    testbed.look_at(Point3::new(-100.0, 0.0, 0.0), Point3::origin());
+}
+
+fn main() {
+    let testbed = Testbed::from_builders(0, vec![("Boxes", init_world)]);
+    testbed.run()
+}