在Unity中旋转带有铰接子项的2D GameObject时的怪异行为

Question

For more than two days now I am struggling with this seemingly impossible problem: I have a composite GameObject (one parent, 10 children), each one hinged to at least another with angle limits and player-controlled motors. Moves perfectly as I wish. Now I want to be able to flip it. After a while and many trials,rotation seems the best way in order to keep the angles (inverting localSpace does not respect them):

Vector3 rotPoint = new Vector3 (ParentGameObject.transform.position.x, myY, myZ);
ParentGameObject.transform.rotateAround (rotPoint, Vector3.up, 180.0f);

BUT, if the parent rotates as asked (180 degrees around its Y axis), every child flips but not around the same axis, rather around their own rotation center. This gives ridiculous results as hinges try to get back to the desired position. How could I fix this? Many many thanks in advance...

Answer 1

In the end I figured out the problem. My problem had no valuable solution.

We can rotate the transform around the Y axis even in 2D, but NOT the rigidbody2D, which in the same object will invariably cause serious problems.

This is maybe one remaining inconsistency into Unity5's implementation of 2D. I had to flip using localScale inversion and programmatically updated positions and rotations.

Answer 2

It sounds like the child GameObjects are rotating around their own pivots instead of the parents. I haven't got Unity installed at the moment to test this, but if you add an empty GameObject as a child of your parent (and with the same pivot point), then make all your other GameObjects a child of this, it should work.

Answer 3

You should not move or rotate a rigidbody if you don't have to. That will mess up the underlying physics calculations and physics engines won't be happy about it. Instead, you have other ways to interact with them

• Apply force, torque
• Apply acceleration, angular acceleration
• Change speed, angular speed

If you have to move/rotate the object, you should also update positions, rotations, speeds, angular speeds of all of your hinged objects. That would not be easy. Give some more details if you unable to solve.