feat: add warmstarting to contact constraints resolution

examples2d/s2d_confined.rs

@@ -0,0 +1,65 @@
+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();
+
+    let radius = 0.5;
+    let grid_count = 25;
+    let friction = 0.6;
+    let max_count = grid_count * grid_count;
+
+    /*
+     * Ground
+     */
+    let collider =
+        ColliderBuilder::capsule(point![-10.5, 0.0], point![10.5, 0.0], radius).friction(friction);
+    colliders.insert(collider);
+    let collider = ColliderBuilder::capsule(point![-10.5, 0.0], point![-10.5, 20.5], radius)
+        .friction(friction);
+    colliders.insert(collider);
+    let collider =
+        ColliderBuilder::capsule(point![10.5, 0.0], point![10.5, 20.5], radius).friction(friction);
+    colliders.insert(collider);
+    let collider = ColliderBuilder::capsule(point![-10.5, 20.5], point![10.5, 20.5], radius)
+        .friction(friction);
+    colliders.insert(collider);
+
+    /*
+     * Create the spheres
+     */
+    let mut row = 0;
+    let mut count = 0;
+    let mut column = 0;
+
+    while count < max_count {
+        row = 0;
+        for i in 0..grid_count {
+            let x = -8.75 + column as f32 * 18.0 / (grid_count as f32);
+            let y = 1.5 + row as f32 * 18.0 / (grid_count as f32);
+            let body = RigidBodyBuilder::dynamic()
+                .translation(vector![x, y])
+                .gravity_scale(0.0);
+            let body_handle = bodies.insert(body);
+            let ball = ColliderBuilder::ball(radius).friction(friction);
+            colliders.insert_with_parent(ball, body_handle, &mut bodies);
+
+            count += 1;
+            row += 1;
+        }
+
+        column += 1;
+    }
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world(bodies, colliders, impulse_joints, multibody_joints);
+    testbed.look_at(point![0.0, 2.5], 20.0);
+}