added the corresponding ball joint motor for 2d

fyrox-impl/src/scene/dim2/joint.rs

@@ -475,6 +475,34 @@ impl Joint {
         self.set_motor_params(motor_params);
         Ok(())
     }
+    /// Makes the [`BallJoint`] to restore its original orientation with motor torque.
+    ///
+    /// Acts as a flexible fixed joint that tolerates some angular movement and tries to restore the original orientation.
+    ///
+    /// For flexible fixed joints that tolerate some translational movement, consider using a [`PrismaticJoint`] and call [`Self::set_motor_target_position_as_prismatic`].
+    ///
+    /// This function essentially calls [`Self::set_motor_target_angle_as_ball`] with a target angle of 0 radians. It is here to be symmetric with its 3D version, which is more useful in a 3D context.
+    ///
+    /// /// Call [`Self::disable_motor`] to stop the motor and remove the spring effect.
+    ///
+    /// # Arguments
+    /// * `stiffness` - Controls how fast the joint will try to restore its original orientation.
+    /// * `max_torque` - The maximum torque this motor can deliver.
+    /// * `damping` - Penalizes high angular velocities to avoid overshooting the original orientation. A higher damping value will result in a smoother transition to the original orientation.
+    /// # Errors
+    /// If the joint is not a [`BallJoint`], the function will do nothing and return an Err.
+    /// # Notice
+    /// The rigid bodies attached to the joint may fall asleep anytime regardless whether the motor is enabled or not.
+    ///
+    /// To avoid this behavior, call this function periodically or call [`RigidBody::set_can_sleep`] on the rigid bodies with "false".
+    pub fn set_motor_resistive_torque_as_ball(
+        &mut self,
+        stiffness: f32,
+        max_torque: f32,
+        damping: f32,
+    ) -> Result<(), String> {
+        self.set_motor_target_angle_as_ball(0.0, stiffness, max_torque, damping)
+    }
 
     /// Disables the motor of the joint assuming it is a [`BallJoint`] or [`PrismaticJoint`].
     ///