code: function VelocityConstraintPoint() {
    this.rA = Vec2.zero();
    this.rB = Vec2.zero();
    this.normalImpulse = 0;
    this.tangentImpulse = 0;
    this.normalMass = 0;
    this.tangentMass = 0;
    this.velocityBias = 0;
  }
docs: TODO merge with ManifoldPoint