feat: add "compression" debug-example

examples2d/all_examples2.rs

@@ -15,6 +15,7 @@ mod collision_groups2;
 mod convex_polygons2;
 mod damping2;
 mod debug_box_ball2;
+mod debug_compression2;
 mod debug_total_overlap2;
 mod drum2;
 mod heightfield2;
@@ -83,6 +84,7 @@ pub fn main() {
         ("Trimesh", trimesh2::init_world),
         ("Joint motor position", joint_motor_position2::init_world),
         ("(Debug) box ball", debug_box_ball2::init_world),
+        ("(Debug) compression", debug_compression2::init_world),
         ("(Debug) total overlap", debug_total_overlap2::init_world),
     ];
 

examples2d/debug_compression2.rs

@@ -0,0 +1,75 @@
+use rapier2d::prelude::*;
+use rapier_testbed2d::Testbed;
+
+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 width = 75.0;
+    let thickness = 2.0;
+    let ys = [-30.0 - thickness, 30.0 + thickness];
+
+    for y in ys {
+        let rigid_body = RigidBodyBuilder::fixed().translation(vector![0.0, y]);
+        let handle = bodies.insert(rigid_body);
+        let collider = ColliderBuilder::cuboid(width, thickness);
+        colliders.insert_with_parent(collider, handle, &mut bodies);
+    }
+
+    // Build two compression boxes rigid body.
+    let half_height = (ys[1] - ys[0]) / 2.0 - thickness;
+    let xs = [-width + thickness, width - thickness];
+    let mut handles = [RigidBodyHandle::invalid(); 2];
+
+    for i in 0..2 {
+        let rigid_body = RigidBodyBuilder::dynamic().translation(vector![xs[i], 0.0]);
+        let handle = bodies.insert(rigid_body);
+        let collider = ColliderBuilder::cuboid(thickness, half_height);
+        colliders.insert_with_parent(collider, handle, &mut bodies);
+        handles[i] = handle;
+    }
+
+    // Build the balls.
+    let num = 8;
+    let rad = half_height / (num as f32);
+    for i in 0..num {
+        for j in 0..num {
+            let x = i as f32 * rad * 2.0 - num as f32 * rad;
+            let y = j as f32 * rad * 2.0 - num as f32 * rad + rad;
+            let rigid_body = RigidBodyBuilder::dynamic().translation(vector![x, y]);
+            let handle = bodies.insert(rigid_body);
+            let collider = ColliderBuilder::ball(rad);
+            colliders.insert_with_parent(collider, handle, &mut bodies);
+        }
+    }
+
+    let mut force = vector![0.0, 0.0];
+
+    testbed.add_callback(move |_, physics, _, _| {
+        let left_plank = &mut physics.bodies[handles[0]];
+        left_plank.reset_forces(true);
+        left_plank.add_force(force, true);
+
+        let right_plank = &mut physics.bodies[handles[1]];
+        right_plank.reset_forces(true);
+        right_plank.add_force(-force, true);
+
+        force.x += 10000.0;
+
+        println!("force: {}", force.x);
+    });
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world(bodies, colliders, impulse_joints, multibody_joints);
+    testbed.look_at(point![0.0, 0.0], 50.0);
+}