Projection friction impulses on an implicit cone instead of a pyramidal approximation.

1 files changed, 114 insertions, 44 deletions

diff --git a/src/dynamics/solver/velocity_ground_constraint.rs b/src/dynamics/solver/velocity_ground_constraint.rs
index 4e195cd..78afd39 100644
--- a/src/dynamics/solver/velocity_ground_constraint.rs
+++ b/src/dynamics/solver/velocity_ground_constraint.rs
@@ -1,13 +1,42 @@
 use super::{AnyVelocityConstraint, DeltaVel};
 use crate::math::{AngVector, Real, Vector, DIM, MAX_MANIFOLD_POINTS};
-use crate::utils::{WAngularInertia, WBasis, WCross, WDot};
+#[cfg(feature = "dim2")]
+use crate::utils::WBasis;
+use crate::utils::{WAngularInertia, WCross, WDot};
 
 use crate::dynamics::{IntegrationParameters, RigidBodySet};
 use crate::geometry::{ContactManifold, ContactManifoldIndex};
-use simba::simd::SimdPartialOrd;
+#[cfg(feature = "dim2")]
+use na::SimdPartialOrd;
 
 #[derive(Copy, Clone, Debug)]
-pub(crate) struct VelocityGroundConstraintElementPart {
+pub(crate) struct VelocityGroundConstraintTangentPart {
+    pub gcross2: [AngVector<Real>; DIM - 1],
+    pub rhs: [Real; DIM - 1],
+    #[cfg(feature = "dim2")]
+    pub impulse: [Real; DIM - 1],
+    #[cfg(feature = "dim3")]
+    pub impulse: na::Vector2<Real>,
+    pub r: [Real; DIM - 1],
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+impl VelocityGroundConstraintTangentPart {
+    fn zero() -> Self {
+        Self {
+            gcross2: [na::zero(); DIM - 1],
+            rhs: [0.0; DIM - 1],
+            #[cfg(feature = "dim2")]
+            impulse: [0.0; DIM - 1],
+            #[cfg(feature = "dim3")]
+            impulse: na::zero(),
+            r: [0.0; DIM - 1],
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct VelocityGroundConstraintNormalPart {
     pub gcross2: AngVector<Real>,
     pub rhs: Real,
     pub impulse: Real,
@@ -15,7 +44,7 @@ pub(crate) struct VelocityGroundConstraintElementPart {
 }
 
 #[cfg(not(target_arch = "wasm32"))]
-impl VelocityGroundConstraintElementPart {
+impl VelocityGroundConstraintNormalPart {
     fn zero() -> Self {
         Self {
             gcross2: na::zero(),
@@ -28,16 +57,16 @@ impl VelocityGroundConstraintElementPart {
 
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct VelocityGroundConstraintElement {
-    pub normal_part: VelocityGroundConstraintElementPart,
-    pub tangent_part: [VelocityGroundConstraintElementPart; DIM - 1],
+    pub normal_part: VelocityGroundConstraintNormalPart,
+    pub tangent_part: VelocityGroundConstraintTangentPart,
 }
 
 #[cfg(not(target_arch = "wasm32"))]
 impl VelocityGroundConstraintElement {
     pub fn zero() -> Self {
         Self {
-            normal_part: VelocityGroundConstraintElementPart::zero(),
-            tangent_part: [VelocityGroundConstraintElementPart::zero(); DIM - 1],
+            normal_part: VelocityGroundConstraintNormalPart::zero(),
+            tangent_part: VelocityGroundConstraintTangentPart::zero(),
         }
     }
 }
@@ -45,6 +74,10 @@ impl VelocityGroundConstraintElement {
 #[derive(Copy, Clone, Debug)]
 pub(crate) struct VelocityGroundConstraint {
     pub dir1: Vector<Real>, // Non-penetration force direction for the first body.
+    #[cfg(feature = "dim3")]
+    pub tangent1: Vector<Real>, // One of the friction force directions.
+    #[cfg(feature = "dim3")]
+    pub tangent_rot1: na::UnitComplex<Real>, // Orientation of the tangent basis wrt. the reference basis.
     pub im2: Real,
     pub limit: Real,
     pub mj_lambda2: usize,
@@ -77,6 +110,12 @@ impl VelocityGroundConstraint {
             (-manifold.data.normal, 1.0)
         };
 
+        #[cfg(feature = "dim2")]
+        let tangents1 = force_dir1.orthonormal_basis();
+        #[cfg(feature = "dim3")]
+        let (tangents1, tangent_rot1) =
+            super::compute_tangent_contact_directions(&force_dir1, &rb1.linvel, &rb2.linvel);
+
         let mj_lambda2 = rb2.active_set_offset;
         let warmstart_coeff = manifold.data.warmstart_multiplier * params.warmstart_coeff;
 
@@ -89,6 +128,10 @@ impl VelocityGroundConstraint {
             #[cfg(not(target_arch = "wasm32"))]
             let mut constraint = VelocityGroundConstraint {
                 dir1: force_dir1,
+                #[cfg(feature = "dim3")]
+                tangent1: tangents1[0],
+                #[cfg(feature = "dim3")]
+                tangent_rot1,
                 elements: [VelocityGroundConstraintElement::zero(); MAX_MANIFOLD_POINTS],
                 im2: rb2.effective_inv_mass,
                 limit: 0.0,
@@ -166,7 +209,7 @@ impl VelocityGroundConstraint {
                     rhs *= is_bouncy + is_resting * params.velocity_solve_fraction;
                     rhs += is_resting * velocity_based_erp_inv_dt * manifold_point.dist.min(0.0);
 
-                    constraint.elements[k].normal_part = VelocityGroundConstraintElementPart {
+                    constraint.elements[k].normal_part = VelocityGroundConstraintNormalPart {
                         gcross2,
                         rhs,
                         impulse: manifold_point.data.impulse * warmstart_coeff,
@@ -176,7 +219,12 @@ impl VelocityGroundConstraint {
 
                 // Tangent parts.
                 {
-                    let tangents1 = force_dir1.orthonormal_basis();
+                    #[cfg(feature = "dim3")]
+                    let impulse =
+                        tangent_rot1 * manifold_points[k].data.tangent_impulse * warmstart_coeff;
+                    #[cfg(feature = "dim2")]
+                    let impulse = [manifold_points[k].data.tangent_impulse * warmstart_coeff];
+                    constraint.elements[k].tangent_part.impulse = impulse;
 
                     for j in 0..DIM - 1 {
                         let gcross2 = rb2
@@ -186,18 +234,10 @@ impl VelocityGroundConstraint {
                         let rhs = (vel1 - vel2
                             + flipped_multiplier * manifold_point.tangent_velocity)
                             .dot(&tangents1[j]);
-                        #[cfg(feature = "dim2")]
-                        let impulse = manifold_points[k].data.tangent_impulse * warmstart_coeff;
-                        #[cfg(feature = "dim3")]
-                        let impulse = manifold_points[k].data.tangent_impulse[j] * warmstart_coeff;
-
-                        constraint.elements[k].tangent_part[j] =
-                            VelocityGroundConstraintElementPart {
-                                gcross2,
-                                rhs,
-                                impulse,
-                                r,
-                            };
+
+                        constraint.elements[k].tangent_part.gcross2[j] = gcross2;
+                        constraint.elements[k].tangent_part.rhs[j] = rhs;
+                        constraint.elements[k].tangent_part.r[j] = r;
                     }
                 }
             }
@@ -214,6 +254,9 @@ impl VelocityGroundConstraint {
 
     pub fn warmstart(&self, mj_lambdas: &mut [DeltaVel<Real>]) {
         let mut mj_lambda2 = DeltaVel::zero();
+        #[cfg(feature = "dim3")]
+        let tangents1 = [self.tangent1, self.dir1.cross(&self.tangent1)];
+        #[cfg(feature = "dim2")]
         let tangents1 = self.dir1.orthonormal_basis();
 
         for i in 0..self.num_contacts as usize {
@@ -222,9 +265,9 @@ impl VelocityGroundConstraint {
             mj_lambda2.angular += elt.gcross2 * elt.impulse;
 
             for j in 0..DIM - 1 {
-                let elt = &self.elements[i].tangent_part[j];
-                mj_lambda2.linear += tangents1[j] * (-self.im2 * elt.impulse);
-                mj_lambda2.angular += elt.gcross2 * elt.impulse;
+                let elt = &self.elements[i].tangent_part;
+                mj_lambda2.linear += tangents1[j] * (-self.im2 * elt.impulse[j]);
+                mj_lambda2.angular += elt.gcross2[j] * elt.impulse[j];
             }
         }
 
@@ -236,23 +279,51 @@ impl VelocityGroundConstraint {
         let mut mj_lambda2 = mj_lambdas[self.mj_lambda2 as usize];
 
         // Solve friction.
+        #[cfg(feature = "dim3")]
+        let bitangent1 = self.dir1.cross(&self.tangent1);
+        #[cfg(feature = "dim2")]
         let tangents1 = self.dir1.orthonormal_basis();
 
+        #[cfg(feature = "dim2")]
         for i in 0..self.num_contacts as usize {
-            for j in 0..DIM - 1 {
-                let normal_elt = &self.elements[i].normal_part;
-                let elt = &mut self.elements[i].tangent_part[j];
-                let dimpulse = -tangents1[j].dot(&mj_lambda2.linear)
-                    + elt.gcross2.gdot(mj_lambda2.angular)
-                    + elt.rhs;
-                let limit = self.limit * normal_elt.impulse;
-                let new_impulse = (elt.impulse - elt.r * dimpulse).simd_clamp(-limit, limit);
-                let dlambda = new_impulse - elt.impulse;
-                elt.impulse = new_impulse;
-
-                mj_lambda2.linear += tangents1[j] * (-self.im2 * dlambda);
-                mj_lambda2.angular += elt.gcross2 * dlambda;
-            }
+            let normal_elt = &self.elements[i].normal_part;
+            let elt = &mut self.elements[i].tangent_part;
+            let dimpulse = -tangents1[0].dot(&mj_lambda2.linear)
+                + elt.gcross2[0].gdot(mj_lambda2.angular)
+                + elt.rhs[0];
+            let limit = self.limit * normal_elt.impulse;
+            let new_impulse = (elt.impulse[0] - elt.r[0] * dimpulse).simd_clamp(-limit, limit);
+            let dlambda = new_impulse - elt.impulse[0];
+            elt.impulse[0] = new_impulse;
+
+            mj_lambda2.linear += tangents1[0] * (-self.im2 * dlambda);
+            mj_lambda2.angular += elt.gcross2[0] * dlambda;
+        }
+
+        #[cfg(feature = "dim3")]
+        for i in 0..self.num_contacts as usize {
+            let limit = self.limit * self.elements[i].normal_part.impulse;
+            let elts = &mut self.elements[i].tangent_part;
+
+            let dimpulse_0 = -self.tangent1.dot(&mj_lambda2.linear)
+                + elts.gcross2[0].gdot(mj_lambda2.angular)
+                + elts.rhs[0];
+            let dimpulse_1 = -bitangent1.dot(&mj_lambda2.linear)
+                + elts.gcross2[1].gdot(mj_lambda2.angular)
+                + elts.rhs[1];
+
+            let new_impulse = na::Vector2::new(
+                elts.impulse[0] - elts.r[0] * dimpulse_0,
+                elts.impulse[1] - elts.r[1] * dimpulse_1,
+            );
+            let new_impulse = new_impulse.cap_magnitude(limit);
+            let dlambda = new_impulse - elts.impulse;
+
+            elts.impulse = new_impulse;
+
+            mj_lambda2.linear +=
+                self.tangent1 * (-self.im2 * dlambda[0]) + bitangent1 * (-self.im2 * dlambda[1]);
+            mj_lambda2.angular += elts.gcross2[0] * dlambda[0] + elts.gcross2[1] * dlambda[1];
         }
 
         // Solve penetration.
@@ -281,14 +352,13 @@ impl VelocityGroundConstraint {
             active_contact.data.impulse = self.elements[k].normal_part.impulse;
             #[cfg(feature = "dim2")]
             {
-                active_contact.data.tangent_impulse = self.elements[k].tangent_part[0].impulse;
+                active_contact.data.tangent_impulse = self.elements[k].tangent_part.impulse[0];
             }
             #[cfg(feature = "dim3")]
             {
-                active_contact.data.tangent_impulse = [
-                    self.elements[k].tangent_part[0].impulse,
-                    self.elements[k].tangent_part[1].impulse,
-                ];
+                active_contact.data.tangent_impulse = self
+                    .tangent_rot1
+                    .inverse_transform_vector(&self.elements[k].tangent_part.impulse);
             }
         }
     }