Anybody know about physics joint limts? I want to make a snake

Unity Engine
1

Hi All,

Essentialy I am trying to set up a chain of rigidbody objects that link from one to the next but with a limit in how far they can angle from each other. So for example imagine it in 2d, a line of vertically linked cubes that should be allowed to move from -20 degrees to + 20 degrees at each link. Ive tried hinge joints and configurable joints, using limits on both, but limits just dont work. If you move the chain or its attched anchor (say a kinematic node at the top) the joints all go way out of the limits set and take ages to resettle.

Are limits broken? Because they certainly dont trap the object to within those values.

I sort of want to achieve the joints you can see above
(but without the restriction being a physical block of the actual joint shapes hitting each other to restrict the angles)

2

Wow, its been so long since i seen one of those. They use to make them out of wood when i was little. Any way why not make a snake with bones like everybody else?

3

OK how would i do this then.
The important part is that each bone should never rotate more than a -20+20 degree from its parent
I cant find any way to do this in unity.
The support seems pretty quiet on this issue, Ive seen alot of posts about how the hinge/joint limits just dont work once you have more than a few hinges in a chain. Nobody seems to have an answer. Im beginning to think its just a failure on the part of the PhysX engine.

4

I’ve found that configurable joints will often work better in chains if you add a little bit of linear movement (set the linear limit to a value that is small in comparison to the segment sizes. This seems to allow the physics some slack in calculating the propagation of forces along the chain and avoid feedback.

5

Well Limiting bones is a easy thing to do. But the real Q is what type of movement are you going for(eg)Animation or script. Are you trying to create the kind of physics the toy snake has, where by tilting the tail the snake falls and coils that direction. Or are you wanting to make the snake do all kinds of movements based on predesigned movements. If you wanted you could just use transforms linked as children,each with a rigidbody. Scripted so that they never rotate to far compared to there own parents position.