tangent_force = ok

src/dynamics/solver/contact_constraint/one_body_constraint.rs

@@ -411,6 +411,10 @@ impl OneBodyConstraint {
             active_contact.data.warmstart_tangent_impulse = self.elements[k].tangent_part.impulse;
             active_contact.data.impulse = self.elements[k].normal_part.total_impulse();
             active_contact.data.tangent_impulse = self.elements[k].tangent_part.total_impulse();
+            #[cfg(feature = "dim3")]
+            {
+                active_contact.data.tangent1 = self.tangent1;
+            }
         }
     }
 

src/dynamics/solver/contact_constraint/one_body_constraint_simd.rs

@@ -412,6 +412,8 @@ impl OneBodyConstraintSimd {
                     warmstart_tangent_impulses.extract(ii);
                 active_contact.data.impulse = impulses[ii];
                 active_contact.data.tangent_impulse = tangent_impulses.extract(ii);
+                #[cfg(feature = "dim3")]
+                active_contact.data.set_tangent1(self.tangent1.extract(ii));
             }
         }
     }

src/dynamics/solver/contact_constraint/two_body_constraint.rs

@@ -481,6 +481,10 @@ impl TwoBodyConstraint {
             active_contact.data.warmstart_tangent_impulse = self.elements[k].tangent_part.impulse;
             active_contact.data.impulse = self.elements[k].normal_part.total_impulse();
             active_contact.data.tangent_impulse = self.elements[k].tangent_part.total_impulse();
+            #[cfg(feature = "dim3")]
+            {
+                active_contact.data.tangent1 = self.tangent1;
+            }
         }
     }
 

src/dynamics/solver/contact_constraint/two_body_constraint_simd.rs

@@ -419,6 +419,8 @@ impl TwoBodyConstraintSimd {
                     warmstart_tangent_impulses.extract(ii);
                 active_contact.data.impulse = impulses[ii];
                 active_contact.data.tangent_impulse = tangent_impulses.extract(ii);
+                #[cfg(feature = "dim3")]
+                active_contact.data.set_tangent1(self.tangent1.extract(ii));
             }
         }
     }

src/geometry/contact_pair.rs

@@ -38,6 +38,9 @@ pub struct ContactData {
     /// The friction impulse along the vector orthonormal to the contact normal, applied to the first
     /// collider's rigid-body.
     pub tangent_impulse: TangentImpulse<Real>,
+    #[cfg(feature = "dim3")]
+    /// One of the friction force directions.
+    pub tangent1: Vector<Real>,
     /// The impulse retained for warmstarting the next simulation step.
     pub warmstart_impulse: Real,
     /// The friction impulse retained for warmstarting the next simulation step.
@@ -51,6 +54,8 @@ impl Default for ContactData {
             tangent_impulse: na::zero(),
             warmstart_impulse: 0.0,
             warmstart_tangent_impulse: na::zero(),
+            #[cfg(feature = "dim3")]
+            tangent1: na::zero(),
         }
     }
 }

src/geometry/mod.rs

@@ -134,6 +134,9 @@ pub struct ContactForceEvent {
     pub collider2: ColliderHandle,
     /// The sum of all the forces between the two colliders.
     pub total_force: Vector<Real>,
+    #[cfg(feature = "dim3")]
+    /// The sum of all the tangent forces between the two colliders.
+    pub total_tangent_force: Vector<Real>,
     /// The sum of the magnitudes of each force between the two colliders.
     ///
     /// Note that this is **not** the same as the magnitude of `self.total_force`.
@@ -160,6 +163,18 @@ impl ContactForceEvent {
             let mut total_manifold_impulse = 0.0;
             for pt in m.contacts() {
                 total_manifold_impulse += pt.data.impulse;
+                #[cfg(feature = "dim3")]
+                {
+                    let tangents1 = [
+                        &pt.data.tangent1,
+                        &(-m.data.normal).cross(&pt.data.tangent1),
+                    ];
+
+                    let tangent_impulse = tangents1[0] * pt.data.warmstart_tangent_impulse[0]
+                        + tangents1[1] * pt.data.warmstart_tangent_impulse[1];
+
+                    result.total_tangent_force += tangent_impulse;
+                }
 
                 if pt.data.impulse > result.max_force_magnitude {
                     result.max_force_magnitude = pt.data.impulse;
@@ -176,6 +191,10 @@ impl ContactForceEvent {
         //       because it’s an input of this function already
         //       assumed to be a force instead of an impulse.
         result.total_force *= inv_dt;
+        #[cfg(feature = "dim3")]
+        {
+            result.total_tangent_force *= inv_dt;
+        }
         result.max_force_magnitude *= inv_dt;
         result
     }