Fix constraints resolution with non-identity relative collider position.

src/dynamics/solver/position_constraint.rs

@@ -104,8 +104,8 @@ impl PositionConstraint {
             let mut local_p2 = [Point::origin(); MAX_MANIFOLD_POINTS];
 
             for l in 0..manifold_points.len() {
-                local_p1[l] = manifold_points[l].local_p1 + shift1;
+                local_p1[l] = manifold.delta1 * (manifold_points[l].local_p1 + shift1);
-                local_p2[l] = manifold_points[l].local_p2 + shift2;
+                local_p2[l] = manifold.delta2 * (manifold_points[l].local_p2 + shift2);
             }
 
             let constraint = PositionConstraint {

src/dynamics/solver/position_constraint_wide.rs

@@ -51,6 +51,9 @@ impl WPositionConstraint {
         let radius1 = SimdFloat::from(array![|ii| manifolds[ii].kinematics.radius1; SIMD_WIDTH]);
         let radius2 = SimdFloat::from(array![|ii| manifolds[ii].kinematics.radius2; SIMD_WIDTH]);
 
+        let delta1 = Isometry::from(array![|ii| manifolds[ii].delta1; SIMD_WIDTH]);
+        let delta2 = Isometry::from(array![|ii| manifolds[ii].delta2; SIMD_WIDTH]);
+
         let rb1 = array![|ii| rbs1[ii].active_set_offset; SIMD_WIDTH];
         let rb2 = array![|ii| rbs2[ii].active_set_offset; SIMD_WIDTH];
 
@@ -85,8 +88,8 @@ impl WPositionConstraint {
                 let local_p2 =
                     Point::from(array![|ii| manifold_points[ii][i].local_p2; SIMD_WIDTH]);
 
-                constraint.local_p1[i] = local_p1 + shift1;
+                constraint.local_p1[i] = delta1 * (local_p1 + shift1);
-                constraint.local_p2[i] = local_p2 + shift2;
+                constraint.local_p2[i] = delta2 * (local_p2 + shift2);
             }
 
             if push {

src/dynamics/solver/position_ground_constraint.rs

@@ -34,22 +34,30 @@ impl PositionGroundConstraint {
 
         let local_n1;
         let local_n2;
+        let delta1;
+        let delta2;
 
         if flip {
             std::mem::swap(&mut rb1, &mut rb2);
             local_n1 = manifold.local_n2;
             local_n2 = manifold.local_n1;
+            delta1 = &manifold.delta2;
+            delta2 = &manifold.delta1;
         } else {
             local_n1 = manifold.local_n1;
             local_n2 = manifold.local_n2;
+            delta1 = &manifold.delta1;
+            delta2 = &manifold.delta2;
         };
 
+        let coll_pos1 = rb1.position * delta1;
         let shift1 = local_n1 * -manifold.kinematics.radius1;
         let shift2 = local_n2 * -manifold.kinematics.radius2;
+        let n1 = coll_pos1 * local_n1;
         let radius =
             manifold.kinematics.radius1 + manifold.kinematics.radius2 /* - params.allowed_linear_error */;
 
-        for (l, manifold_points) in manifold
+        for (l, manifold_contacts) in manifold
             .active_contacts()
             .chunks(MAX_MANIFOLD_POINTS)
             .enumerate()
@@ -59,16 +67,16 @@ impl PositionGroundConstraint {
 
             if flip {
                 // Don't forget that we already swapped rb1 and rb2 above.
-                // So if we flip, only manifold_points[k].{local_p1,local_p2} have to
+                // So if we flip, only manifold_contacts[k].{local_p1,local_p2} have to
                 // be swapped.
-                for k in 0..manifold_points.len() {
+                for k in 0..manifold_contacts.len() {
-                    p1[k] = rb1.predicted_position * (manifold_points[k].local_p2 + shift1);
+                    p1[k] = coll_pos1 * (manifold_contacts[k].local_p2 + shift1);
-                    local_p2[k] = manifold_points[k].local_p1 + shift2;
+                    local_p2[k] = delta2 * (manifold_contacts[k].local_p1 + shift2);
                 }
             } else {
-                for k in 0..manifold_points.len() {
+                for k in 0..manifold_contacts.len() {
-                    p1[k] = rb1.predicted_position * (manifold_points[k].local_p1 + shift1);
+                    p1[k] = coll_pos1 * (manifold_contacts[k].local_p1 + shift1);
-                    local_p2[k] = manifold_points[k].local_p2 + shift2;
+                    local_p2[k] = delta2 * (manifold_contacts[k].local_p2 + shift2);
                 }
             }
 
@@ -76,11 +84,11 @@ impl PositionGroundConstraint {
                 rb2: rb2.active_set_offset,
                 p1,
                 local_p2,
-                n1: rb1.predicted_position * local_n1,
+                n1,
                 radius,
                 im2: rb2.mass_properties.inv_mass,
                 ii2: rb2.world_inv_inertia_sqrt.squared(),
-                num_contacts: manifold_points.len() as u8,
+                num_contacts: manifold_contacts.len() as u8,
                 erp: params.erp,
                 max_linear_correction: params.max_linear_correction,
             };

src/dynamics/solver/position_ground_constraint_wide.rs

@@ -54,16 +54,24 @@ impl WPositionGroundConstraint {
             array![|ii| if flipped[ii] { manifolds[ii].local_n1 } else { manifolds[ii].local_n2 }; SIMD_WIDTH],
         );
 
+        let delta1 = Isometry::from(
+            array![|ii| if flipped[ii] { manifolds[ii].delta2 } else { manifolds[ii].delta1 }; SIMD_WIDTH],
+        );
+        let delta2 = Isometry::from(
+            array![|ii| if flipped[ii] { manifolds[ii].delta1 } else { manifolds[ii].delta2 }; SIMD_WIDTH],
+        );
+
         let radius1 = SimdFloat::from(array![|ii| manifolds[ii].kinematics.radius1; SIMD_WIDTH]);
         let radius2 = SimdFloat::from(array![|ii| manifolds[ii].kinematics.radius2; SIMD_WIDTH]);
 
-        let position1 = Isometry::from(array![|ii| rbs1[ii].predicted_position; SIMD_WIDTH]);
+        let coll_pos1 =
+            delta1 * Isometry::from(array![|ii| rbs1[ii].predicted_position; SIMD_WIDTH]);
 
         let rb2 = array![|ii| rbs2[ii].active_set_offset; SIMD_WIDTH];
 
         let radius = radius1 + radius2 /*- SimdFloat::splat(params.allowed_linear_error)*/;
 
-        let n1 = position1 * local_n1;
+        let n1 = coll_pos1 * local_n1;
 
         for l in (0..manifolds[0].num_active_contacts()).step_by(MAX_MANIFOLD_POINTS) {
             let manifold_points = array![|ii| &manifolds[ii].active_contacts()[l..]; SIMD_WIDTH];
@@ -90,8 +98,8 @@ impl WPositionGroundConstraint {
                     array![|ii| if flipped[ii] { manifold_points[ii][i].local_p1 } else { manifold_points[ii][i].local_p2 }; SIMD_WIDTH],
                 );
 
-                constraint.p1[i] = position1 * local_p1 - n1 * radius1;
+                constraint.p1[i] = coll_pos1 * local_p1 - n1 * radius1;
-                constraint.local_p2[i] = local_p2 - local_n2 * radius2;
+                constraint.local_p2[i] = delta2 * (local_p2 - local_n2 * radius2);
             }
 
             if push {

src/dynamics/solver/velocity_constraint.rs

@@ -148,7 +148,9 @@ impl VelocityConstraint {
         let rb2 = &bodies[manifold.body_pair.body2];
         let mj_lambda1 = rb1.active_set_offset;
         let mj_lambda2 = rb2.active_set_offset;
-        let force_dir1 = rb1.position * (-manifold.local_n1);
+        let pos_coll1 = rb1.position * manifold.delta1;
+        let pos_coll2 = rb2.position * manifold.delta2;
+        let force_dir1 = pos_coll1 * (-manifold.local_n1);
         let warmstart_coeff = manifold.warmstart_multiplier * params.warmstart_coeff;
 
         for (l, manifold_points) in manifold
@@ -215,8 +217,8 @@ impl VelocityConstraint {
 
             for k in 0..manifold_points.len() {
                 let manifold_point = &manifold_points[k];
-                let dp1 = (rb1.position * manifold_point.local_p1) - rb1.world_com;
+                let dp1 = (pos_coll1 * manifold_point.local_p1) - rb1.world_com;
-                let dp2 = (rb2.position * manifold_point.local_p2) - rb2.world_com;
+                let dp2 = (pos_coll2 * manifold_point.local_p2) - rb2.world_com;
 
                 let vel1 = rb1.linvel + rb1.angvel.gcross(dp1);
                 let vel2 = rb2.linvel + rb2.angvel.gcross(dp2);

src/dynamics/solver/velocity_constraint_wide.rs

@@ -72,6 +72,9 @@ impl WVelocityConstraint {
         let rbs1 = array![|ii| &bodies[manifolds[ii].body_pair.body1]; SIMD_WIDTH];
         let rbs2 = array![|ii| &bodies[manifolds[ii].body_pair.body2]; SIMD_WIDTH];
 
+        let delta1 = Isometry::from(array![|ii| manifolds[ii].delta1; SIMD_WIDTH]);
+        let delta2 = Isometry::from(array![|ii| manifolds[ii].delta2; SIMD_WIDTH]);
+
         let im1 = SimdFloat::from(array![|ii| rbs1[ii].mass_properties.inv_mass; SIMD_WIDTH]);
         let ii1: AngularInertia<SimdFloat> =
             AngularInertia::from(array![|ii| rbs1[ii].world_inv_inertia_sqrt; SIMD_WIDTH]);
@@ -79,7 +82,7 @@ impl WVelocityConstraint {
         let linvel1 = Vector::from(array![|ii| rbs1[ii].linvel; SIMD_WIDTH]);
         let angvel1 = AngVector::<SimdFloat>::from(array![|ii| rbs1[ii].angvel; SIMD_WIDTH]);
 
-        let position1 = Isometry::from(array![|ii| rbs1[ii].position; SIMD_WIDTH]);
+        let pos1 = Isometry::from(array![|ii| rbs1[ii].position; SIMD_WIDTH]);
         let world_com1 = Point::from(array![|ii| rbs1[ii].world_com; SIMD_WIDTH]);
 
         let im2 = SimdFloat::from(array![|ii| rbs2[ii].mass_properties.inv_mass; SIMD_WIDTH]);
@@ -89,10 +92,13 @@ impl WVelocityConstraint {
         let linvel2 = Vector::from(array![|ii| rbs2[ii].linvel; SIMD_WIDTH]);
         let angvel2 = AngVector::<SimdFloat>::from(array![|ii| rbs2[ii].angvel; SIMD_WIDTH]);
 
-        let position2 = Isometry::from(array![|ii| rbs2[ii].position; SIMD_WIDTH]);
+        let pos2 = Isometry::from(array![|ii| rbs2[ii].position; SIMD_WIDTH]);
         let world_com2 = Point::from(array![|ii| rbs2[ii].world_com; SIMD_WIDTH]);
 
-        let force_dir1 = position1 * -Vector::from(array![|ii| manifolds[ii].local_n1; SIMD_WIDTH]);
+        let coll_pos1 = pos1 * delta1;
+        let coll_pos2 = pos2 * delta2;
+
+        let force_dir1 = coll_pos1 * -Vector::from(array![|ii| manifolds[ii].local_n1; SIMD_WIDTH]);
 
         let mj_lambda1 = array![|ii| rbs1[ii].active_set_offset; SIMD_WIDTH];
         let mj_lambda2 = array![|ii| rbs2[ii].active_set_offset; SIMD_WIDTH];
@@ -120,11 +126,11 @@ impl WVelocityConstraint {
             };
 
             for k in 0..num_points {
-                // FIXME: can we avoid the multiplications by position1/position2 here?
+                // FIXME: can we avoid the multiplications by coll_pos1/coll_pos2 here?
                 // By working as much as possible in local-space.
-                let p1 = position1
+                let p1 = coll_pos1
                     * Point::from(array![|ii| manifold_points[ii][k].local_p1; SIMD_WIDTH]);
-                let p2 = position2
+                let p2 = coll_pos2
                     * Point::from(array![|ii| manifold_points[ii][k].local_p2; SIMD_WIDTH]);
 
                 let dist = SimdFloat::from(array![|ii| manifold_points[ii][k].dist; SIMD_WIDTH]);

src/dynamics/solver/velocity_ground_constraint.rs

@@ -66,20 +66,22 @@ impl VelocityGroundConstraint {
         let mut rb1 = &bodies[manifold.body_pair.body1];
         let mut rb2 = &bodies[manifold.body_pair.body2];
         let flipped = !rb2.is_dynamic();
+        let force_dir1;
+        let coll_pos1;
+        let coll_pos2;
 
         if flipped {
+            coll_pos1 = rb2.position * manifold.delta2;
+            coll_pos2 = rb1.position * manifold.delta1;
+            force_dir1 = coll_pos1 * (-manifold.local_n2);
             std::mem::swap(&mut rb1, &mut rb2);
+        } else {
+            coll_pos1 = rb1.position * manifold.delta1;
+            coll_pos2 = rb2.position * manifold.delta2;
+            force_dir1 = coll_pos1 * (-manifold.local_n1);
         }
 
         let mj_lambda2 = rb2.active_set_offset;
-        let force_dir1 = if flipped {
-            // NOTE: we already swapped rb1 and rb2
-            // so we multiply by rb1.position.
-            rb1.position * (-manifold.local_n2)
-        } else {
-            rb1.position * (-manifold.local_n1)
-        };
-
         let warmstart_coeff = manifold.warmstart_multiplier * params.warmstart_coeff;
 
         for (l, manifold_points) in manifold
@@ -144,15 +146,15 @@ impl VelocityGroundConstraint {
                 let manifold_point = &manifold_points[k];
                 let (p1, p2) = if flipped {
                     // NOTE: we already swapped rb1 and rb2
-                    // so we multiply by rb2.position.
+                    // so we multiply by coll_pos1/coll_pos2.
                     (
-                        rb1.position * manifold_point.local_p2,
+                        coll_pos1 * manifold_point.local_p2,
-                        rb2.position * manifold_point.local_p1,
+                        coll_pos2 * manifold_point.local_p1,
                     )
                 } else {
                     (
-                        rb1.position * manifold_point.local_p1,
+                        coll_pos1 * manifold_point.local_p1,
-                        rb2.position * manifold_point.local_p2,
+                        coll_pos2 * manifold_point.local_p2,
                     )
                 };
                 let dp2 = p2 - rb2.world_com;

src/dynamics/solver/velocity_ground_constraint_wide.rs

@@ -86,13 +86,23 @@ impl WVelocityGroundConstraint {
         let linvel2 = Vector::from(array![|ii| rbs2[ii].linvel; SIMD_WIDTH]);
         let angvel2 = AngVector::<SimdFloat>::from(array![|ii| rbs2[ii].angvel; SIMD_WIDTH]);
 
-        let position1 = Isometry::from(array![|ii| rbs1[ii].position; SIMD_WIDTH]);
+        let pos1 = Isometry::from(array![|ii| rbs1[ii].position; SIMD_WIDTH]);
-        let position2 = Isometry::from(array![|ii| rbs2[ii].position; SIMD_WIDTH]);
+        let pos2 = Isometry::from(array![|ii| rbs2[ii].position; SIMD_WIDTH]);
+
+        let delta1 = Isometry::from(
+            array![|ii| if flipped[ii] { manifolds[ii].delta2 } else { manifolds[ii].delta1 }; SIMD_WIDTH],
+        );
+        let delta2 = Isometry::from(
+            array![|ii| if flipped[ii] { manifolds[ii].delta1 } else { manifolds[ii].delta2 }; SIMD_WIDTH],
+        );
+
+        let coll_pos1 = pos1 * delta1;
+        let coll_pos2 = pos2 * delta2;
 
         let world_com1 = Point::from(array![|ii| rbs1[ii].world_com; SIMD_WIDTH]);
         let world_com2 = Point::from(array![|ii| rbs2[ii].world_com; SIMD_WIDTH]);
 
-        let force_dir1 = position1
+        let force_dir1 = coll_pos1
             * -Vector::from(
                 array![|ii| if flipped[ii] { manifolds[ii].local_n2 } else { manifolds[ii].local_n1 }; SIMD_WIDTH],
             );
@@ -120,11 +130,11 @@ impl WVelocityGroundConstraint {
             };
 
             for k in 0..num_points {
-                let p1 = position1
+                let p1 = coll_pos1
                     * Point::from(
                         array![|ii| if flipped[ii] { manifold_points[ii][k].local_p2 } else { manifold_points[ii][k].local_p1 }; SIMD_WIDTH],
                     );
-                let p2 = position2
+                let p2 = coll_pos2
                     * Point::from(
                         array![|ii| if flipped[ii] { manifold_points[ii][k].local_p1 } else { manifold_points[ii][k].local_p2 }; SIMD_WIDTH],
                     );

src/geometry/contact.rs

@@ -273,16 +273,21 @@ pub struct ContactManifold {
     /// The pair of subshapes involved in this contact manifold.
     pub subshape_index_pair: (usize, usize),
     pub(crate) warmstart_multiplier: f32,
-    // We put the friction and restitution here because
+    // The two following are set by the constraints solver.
-    // this avoids reading the colliders inside of the
+    pub(crate) constraint_index: usize,
+    pub(crate) position_constraint_index: usize,
+    // We put the following fields here to avoids reading the colliders inside of the
     // contact preparation method.
     /// The friction coefficient for of all the contacts on this contact manifold.
     pub friction: f32,
     /// The restitution coefficient for all the contacts on this contact manifold.
     pub restitution: f32,
-    // The following are set by the constraints solver.
+    /// The relative position between the first collider and its parent at the time the
-    pub(crate) constraint_index: usize,
+    /// contact points were generated.
-    pub(crate) position_constraint_index: usize,
+    pub delta1: Isometry<f32>,
+    /// The relative position between the second collider and its parent at the time the
+    /// contact points were generated.
+    pub delta2: Isometry<f32>,
 }
 
 impl ContactManifold {
@@ -290,6 +295,8 @@ impl ContactManifold {
         pair: ColliderPair,
         subshapes: (usize, usize),
         body_pair: BodyPair,
+        delta1: Isometry<f32>,
+        delta2: Isometry<f32>,
         friction: f32,
         restitution: f32,
     ) -> ContactManifold {
@@ -308,6 +315,8 @@ impl ContactManifold {
             warmstart_multiplier: Self::min_warmstart_multiplier(),
             friction,
             restitution,
+            delta1,
+            delta2,
             constraint_index: 0,
             position_constraint_index: 0,
         }
@@ -329,6 +338,8 @@ impl ContactManifold {
             warmstart_multiplier: self.warmstart_multiplier,
             friction: self.friction,
             restitution: self.restitution,
+            delta1: self.delta1,
+            delta2: self.delta2,
             constraint_index: self.constraint_index,
             position_constraint_index: self.position_constraint_index,
         }
@@ -349,6 +360,8 @@ impl ContactManifold {
             pair,
             (subshape1, subshape2),
             BodyPair::new(coll1.parent, coll2.parent),
+            *coll1.delta(),
+            *coll2.delta(),
             (coll1.friction + coll2.friction) * 0.5,
             (coll1.restitution + coll2.restitution) * 0.5,
         )
@@ -391,6 +404,7 @@ impl ContactManifold {
         self.pair = self.pair.swap();
         self.body_pair = self.body_pair.swap();
         self.subshape_index_pair = (self.subshape_index_pair.1, self.subshape_index_pair.0);
+        std::mem::swap(&mut self.delta1, &mut self.delta2);
     }
 
     pub(crate) fn update_warmstart_multiplier(&mut self) {

src/geometry/contact_generator/cuboid_cuboid_contact_generator.rs

@@ -10,10 +10,8 @@ pub fn generate_contacts_cuboid_cuboid(ctxt: &mut PrimitiveContactGenerationCont
         generate_contacts(
             ctxt.prediction_distance,
             cube1,
-            ctxt.collider1.position_wrt_parent(),
             ctxt.position1,
             cube2,
-            ctxt.collider2.position_wrt_parent(),
             ctxt.position2,
             ctxt.manifold,
         );
@@ -28,19 +26,15 @@ pub fn generate_contacts_cuboid_cuboid(ctxt: &mut PrimitiveContactGenerationCont
 pub fn generate_contacts<'a>(
     prediction_distance: f32,
     mut cube1: &'a Cuboid<f32>,
-    mut origin1: &'a Isometry<f32>,
     mut pos1: &'a Isometry<f32>,
     mut cube2: &'a Cuboid<f32>,
-    mut origin2: &'a Isometry<f32>,
     mut pos2: &'a Isometry<f32>,
     manifold: &mut ContactManifold,
 ) {
     let mut pos12 = pos1.inverse() * pos2;
     let mut pos21 = pos12.inverse();
-    let mut orig_pos12 = origin1 * pos12 * origin2.inverse();
-    let mut orig_pos21 = orig_pos12.inverse();
 
-    if manifold.try_update_contacts(&orig_pos12) {
+    if manifold.try_update_contacts(&pos12) {
         return;
     }
 
@@ -87,9 +81,8 @@ pub fn generate_contacts<'a>(
     if sep2.0 > sep1.0 && sep2.0 > sep3.0 {
         // The reference shape will be the second shape.
         std::mem::swap(&mut cube1, &mut cube2);
+        std::mem::swap(&mut pos1, &mut pos2);
         std::mem::swap(&mut pos12, &mut pos21);
-        std::mem::swap(&mut orig_pos12, &mut orig_pos21);
-        std::mem::swap(&mut origin1, &mut origin2);
         manifold.swap_identifiers();
         best_sep = sep2;
         swapped = true;
@@ -104,49 +97,46 @@ pub fn generate_contacts<'a>(
 
     // Now the reference feature is from `cube1` and the best separation is `best_sep`.
     // Everything must be expressed in the local-space of `cube1` for contact clipping.
-    let mut feature1 = cuboid::support_feature(cube1, best_sep.1);
+    let feature1 = cuboid::support_feature(cube1, best_sep.1);
-    feature1.transform_by(origin1);
     let mut feature2 = cuboid::support_feature(cube2, pos21 * -best_sep.1);
     feature2.transform_by(&pos12);
-    feature2.transform_by(origin1);
-    let n1 = origin1 * best_sep.1;
 
     match (&feature1, &feature2) {
         (CuboidFeature::Face(f1), CuboidFeature::Vertex(v2)) => {
-            CuboidFeature::face_vertex_contacts(f1, &n1, v2, &orig_pos21, manifold)
+            CuboidFeature::face_vertex_contacts(f1, &best_sep.1, v2, &pos21, manifold)
         }
         #[cfg(feature = "dim3")]
         (CuboidFeature::Face(f1), CuboidFeature::Edge(e2)) => CuboidFeature::face_edge_contacts(
             prediction_distance,
             f1,
-            &n1,
+            &best_sep.1,
             e2,
-            &orig_pos21,
+            &pos21,
             manifold,
             false,
         ),
         (CuboidFeature::Face(f1), CuboidFeature::Face(f2)) => CuboidFeature::face_face_contacts(
             prediction_distance,
             f1,
-            &n1,
+            &best_sep.1,
             f2,
-            &orig_pos21,
+            &pos21,
             manifold,
         ),
         #[cfg(feature = "dim3")]
         (CuboidFeature::Edge(e1), CuboidFeature::Edge(e2)) => {
-            CuboidFeature::edge_edge_contacts(e1, &n1, e2, &orig_pos21, manifold)
+            CuboidFeature::edge_edge_contacts(e1, &best_sep.1, e2, &pos21, manifold)
         }
         #[cfg(feature = "dim3")]
         (CuboidFeature::Edge(e1), CuboidFeature::Face(f2)) => {
             // Since f2 is also expressed in the local-space of the first
-            // feature, the position we provide here is orig_pos21.
+            // feature, the position we provide here is pos21.
             CuboidFeature::face_edge_contacts(
                 prediction_distance,
                 f2,
-                &-n1,
+                &-best_sep.1,
                 e1,
-                &orig_pos21,
+                &pos21,
                 manifold,
                 true,
             )
@@ -154,8 +144,8 @@ pub fn generate_contacts<'a>(
         _ => unreachable!(), // The other cases are not possible.
     }
 
-    manifold.local_n1 = n1;
+    manifold.local_n1 = best_sep.1;
-    manifold.local_n2 = orig_pos21 * -n1;
+    manifold.local_n2 = pos21 * -best_sep.1;
     manifold.kinematics.category = KinematicsCategory::PlanePoint;
     manifold.kinematics.radius1 = 0.0;
     manifold.kinematics.radius2 = 0.0;

src_testbed/nphysics_backend.rs

@@ -13,7 +13,7 @@ use rapier::dynamics::{
     IntegrationParameters, JointParams, JointSet, RigidBodyHandle, RigidBodySet,
 };
 use rapier::geometry::{Collider, ColliderSet, Shape};
-use rapier::math::{Isometry, Vector};
+use rapier::math::Vector;
 use std::collections::HashMap;
 #[cfg(feature = "dim3")]
 use {ncollide::shape::TriMesh, nphysics::joint::BallConstraint};