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use rapier2d::prelude::*;
use rapier_testbed2d::Testbed;
struct OneWayPlatformHook {
platform1: ColliderHandle,
platform2: ColliderHandle,
}
impl PhysicsHooks for OneWayPlatformHook {
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 = Vector::zeros();
if context.collider1 == self.platform1 {
allowed_local_n1 = Vector::y();
} else if context.collider2 == self.platform1 {
// Flip the allowed direction.
allowed_local_n1 = -Vector::y();
}
if context.collider1 == self.platform2 {
allowed_local_n1 = -Vector::y();
} else if context.collider2 == self.platform2 {
// Flip the allowed direction.
allowed_local_n1 = Vector::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.collider1 == self.platform1 || context.collider2 == self.platform2 {
-12.0
} else {
12.0
};
for contact in context.solver_contacts.iter_mut() {
contact.tangent_velocity.x = tangent_velocity;
}
}
}
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 rigid_body = RigidBodyBuilder::fixed();
let handle = bodies.insert(rigid_body);
let collider = ColliderBuilder::cuboid(25.0, 0.5)
.translation(vector![30.0, 2.0])
.active_hooks(ActiveHooks::MODIFY_SOLVER_CONTACTS);
let platform1 = colliders.insert_with_parent(collider, handle, &mut bodies);
let collider = ColliderBuilder::cuboid(25.0, 0.5)
.translation(vector![-30.0, -2.0])
.active_hooks(ActiveHooks::MODIFY_SOLVER_CONTACTS);
let platform2 = colliders.insert_with_parent(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 |graphics, physics, _, run_state| {
if run_state.timestep_id % 200 == 0 && physics.bodies.len() <= 7 {
// Spawn a new cube.
let collider = ColliderBuilder::cuboid(1.5, 2.0);
let body = RigidBodyBuilder::dynamic().translation(vector![20.0, 10.0]);
let handle = physics.bodies.insert(body);
physics
.colliders
.insert_with_parent(collider, handle, &mut physics.bodies);
if let Some(graphics) = graphics {
graphics.add_body(handle, &physics.bodies, &physics.colliders);
}
}
for handle in physics.islands.active_dynamic_bodies() {
let body = &mut physics.bodies[*handle];
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,
impulse_joints,
multibody_joints,
vector![0.0, -9.81],
physics_hooks,
);
testbed.look_at(point![0.0, 0.0], 20.0);
}
|
