Attenuate the warmstart impulse for CCD contacts.

CCD contacts result in very strong, instantaneous, impulses. So it is preferable to attenuate their contribution to subsequent timesteps to avoid overshooting.

1 files changed, 12 insertions, 4 deletions

diff --git a/src/dynamics/solver/velocity_ground_constraint.rs b/src/dynamics/solver/velocity_ground_constraint.rs
index b9c5236..0e195d5 100644
--- a/src/dynamics/solver/velocity_ground_constraint.rs
+++ b/src/dynamics/solver/velocity_ground_constraint.rs
@@ -133,6 +133,7 @@ impl VelocityGroundConstraint {
                 let dp1 = manifold_point.point - rb1.world_com;
                 let vel1 = rb1.linvel + rb1.angvel.gcross(dp1);
                 let vel2 = rb2.linvel + rb2.angvel.gcross(dp2);
+                let warmstart_correction;
 
                 constraint.limit = manifold_point.friction;
                 constraint.manifold_contact_id[k] = manifold_point.contact_id;
@@ -153,11 +154,14 @@ impl VelocityGroundConstraint {
                     rhs += manifold_point.dist.max(0.0) * inv_dt;
                     rhs *= is_bouncy + is_resting * params.velocity_solve_fraction;
                     rhs += is_resting * velocity_based_erp_inv_dt * manifold_point.dist.min(0.0);
+                    warmstart_correction = (params.warmstart_correction_slope
+                        / (rhs - manifold_point.prev_rhs).abs())
+                    .min(warmstart_coeff);
 
                     constraint.elements[k].normal_part = VelocityGroundConstraintNormalPart {
                         gcross2,
                         rhs,
-                        impulse: manifold_point.data.impulse * warmstart_coeff,
+                        impulse: manifold_point.warmstart_impulse * warmstart_correction,
                         r,
                     };
                 }
@@ -165,10 +169,12 @@ impl VelocityGroundConstraint {
                 // Tangent parts.
                 {
                     #[cfg(feature = "dim3")]
-                    let impulse =
-                        tangent_rot1 * manifold_points[k].data.tangent_impulse * warmstart_coeff;
+                    let impulse = tangent_rot1
+                        * manifold_points[k].warmstart_tangent_impulse
+                        * warmstart_correction;
                     #[cfg(feature = "dim2")]
-                    let impulse = [manifold_points[k].data.tangent_impulse * warmstart_coeff];
+                    let impulse =
+                        [manifold_points[k].warmstart_tangent_impulse * warmstart_correction];
                     constraint.elements[k].tangent_part.impulse = impulse;
 
                     for j in 0..DIM - 1 {
@@ -237,6 +243,8 @@ impl VelocityGroundConstraint {
             let contact_id = self.manifold_contact_id[k];
             let active_contact = &mut manifold.points[contact_id as usize];
             active_contact.data.impulse = self.elements[k].normal_part.impulse;
+            active_contact.data.rhs = self.elements[k].normal_part.rhs;
+
             #[cfg(feature = "dim2")]
             {
                 active_contact.data.tangent_impulse = self.elements[k].tangent_part.impulse[0];