Constraint solver: properly take non-zero center of masses into account.

4 files changed, 14 insertions, 11 deletions

diff --git a/src/dynamics/solver/velocity_constraint.rs b/src/dynamics/solver/velocity_constraint.rs
index 9212e89..eb80018 100644
--- a/src/dynamics/solver/velocity_constraint.rs
+++ b/src/dynamics/solver/velocity_constraint.rs
@@ -215,10 +215,8 @@ impl VelocityConstraint {
 
             for k in 0..manifold_points.len() {
                 let manifold_point = &manifold_points[k];
-                let dp1 = (rb1.position * manifold_point.local_p1).coords
-                    - rb1.position.translation.vector;
-                let dp2 = (rb2.position * manifold_point.local_p2).coords
-                    - rb2.position.translation.vector;
+                let dp1 = (rb1.position * manifold_point.local_p1) - rb1.world_com;
+                let dp2 = (rb2.position * manifold_point.local_p2) - rb2.world_com;
 
                 let vel1 = rb1.linvel + rb1.angvel.gcross(dp1);
                 let vel2 = rb2.linvel + rb2.angvel.gcross(dp2);
@@ -355,7 +353,7 @@ impl VelocityConstraint {
             }
         }
 
-        // Solve penetration.
+        // Solve non-penetration.
         for i in 0..self.num_contacts as usize {
             let elt = &mut self.elements[i].normal_part;
             let dimpulse = self.dir1.dot(&mj_lambda1.linear) + elt.gcross1.gdot(mj_lambda1.angular)
diff --git a/src/dynamics/solver/velocity_constraint_wide.rs b/src/dynamics/solver/velocity_constraint_wide.rs
index 8f387a5..4204e68 100644
--- a/src/dynamics/solver/velocity_constraint_wide.rs
+++ b/src/dynamics/solver/velocity_constraint_wide.rs
@@ -80,6 +80,7 @@ impl WVelocityConstraint {
         let angvel1 = AngVector::<SimdFloat>::from(array![|ii| rbs1[ii].angvel; SIMD_WIDTH]);
 
         let position1 = 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]);
         let ii2: AngularInertia<SimdFloat> =
@@ -89,6 +90,7 @@ impl WVelocityConstraint {
         let angvel2 = AngVector::<SimdFloat>::from(array![|ii| rbs2[ii].angvel; SIMD_WIDTH]);
 
         let position2 = 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]);
 
@@ -130,8 +132,8 @@ impl WVelocityConstraint {
                 let impulse =
                     SimdFloat::from(array![|ii| manifold_points[ii][k].impulse; SIMD_WIDTH]);
 
-                let dp1 = p1.coords - position1.translation.vector;
-                let dp2 = p2.coords - position2.translation.vector;
+                let dp1 = p1 - world_com1;
+                let dp2 = p2 - world_com2;
 
                 let vel1 = linvel1 + angvel1.gcross(dp1);
                 let vel2 = linvel2 + angvel2.gcross(dp2);
diff --git a/src/dynamics/solver/velocity_ground_constraint.rs b/src/dynamics/solver/velocity_ground_constraint.rs
index 457c3b3..65a61bd 100644
--- a/src/dynamics/solver/velocity_ground_constraint.rs
+++ b/src/dynamics/solver/velocity_ground_constraint.rs
@@ -155,8 +155,8 @@ impl VelocityGroundConstraint {
                         rb2.position * manifold_point.local_p2,
                     )
                 };
-                let dp2 = p2.coords - rb2.position.translation.vector;
-                let dp1 = p1.coords - rb1.position.translation.vector;
+                let dp2 = p2 - rb2.world_com;
+                let dp1 = p1 - rb1.world_com;
                 let vel1 = rb1.linvel + rb1.angvel.gcross(dp1);
                 let vel2 = rb2.linvel + rb2.angvel.gcross(dp2);
 
diff --git a/src/dynamics/solver/velocity_ground_constraint_wide.rs b/src/dynamics/solver/velocity_ground_constraint_wide.rs
index ec9e186..af2e1e9 100644
--- a/src/dynamics/solver/velocity_ground_constraint_wide.rs
+++ b/src/dynamics/solver/velocity_ground_constraint_wide.rs
@@ -89,6 +89,9 @@ impl WVelocityGroundConstraint {
         let position1 = Isometry::from(array![|ii| rbs1[ii].position; SIMD_WIDTH]);
         let position2 = Isometry::from(array![|ii| rbs2[ii].position; SIMD_WIDTH]);
 
+        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
             * -Vector::from(
                 array![|ii| if flipped[ii] { manifolds[ii].local_n2 } else { manifolds[ii].local_n1 }; SIMD_WIDTH],
@@ -130,8 +133,8 @@ impl WVelocityGroundConstraint {
 
                 let impulse =
                     SimdFloat::from(array![|ii| manifold_points[ii][k].impulse; SIMD_WIDTH]);
-                let dp1 = p1.coords - position1.translation.vector;
-                let dp2 = p2.coords - position2.translation.vector;
+                let dp1 = p1 - world_com1;
+                let dp2 = p2 - world_com2;
 
                 let vel1 = linvel1 + angvel1.gcross(dp1);
                 let vel2 = linvel2 + angvel2.gcross(dp2);