Fix applied rotation from moving platforms in move_and_slide

When synchronizing CharacterBody motion with moving the platform using
direct body state, only the linear velocity was taken into account.

This change exposes velocity at local point in direct body state and
uses it in move_and_slide to get the proper velocity that includes
rotations.

1 files changed, 6 insertions, 0 deletions

diff --git a/servers/physics_2d/body_2d_sw.h b/servers/physics_2d/body_2d_sw.h
index b4a95651cb..74bef433dc 100644
--- a/servers/physics_2d/body_2d_sw.h
+++ b/servers/physics_2d/body_2d_sw.h
@@ -266,6 +266,10 @@ public:
 	void integrate_forces(real_t p_step);
 	void integrate_velocities(real_t p_step);
 
+	_FORCE_INLINE_ Vector2 get_velocity_in_local_point(const Vector2 &rel_pos) const {
+		return linear_velocity + Vector2(-angular_velocity * rel_pos.y, angular_velocity * rel_pos.x);
+	}
+
 	_FORCE_INLINE_ Vector2 get_motion() const {
 		if (mode > PhysicsServer2D::BODY_MODE_KINEMATIC) {
 			return new_transform.get_origin() - get_transform().get_origin();
@@ -352,6 +356,8 @@ public:
 	virtual void set_transform(const Transform2D &p_transform) override { body->set_state(PhysicsServer2D::BODY_STATE_TRANSFORM, p_transform); }
 	virtual Transform2D get_transform() const override { return body->get_transform(); }
 
+	virtual Vector2 get_velocity_at_local_position(const Vector2 &p_position) const override { return body->get_velocity_in_local_point(p_position); }
+
 	virtual void add_central_force(const Vector2 &p_force) override { body->add_central_force(p_force); }
 	virtual void add_force(const Vector2 &p_force, const Vector2 &p_position = Vector2()) override { body->add_force(p_force, p_position); }
 	virtual void add_torque(real_t p_torque) override { body->add_torque(p_torque); }