Wondering how to make a squash and stretch ball rig for use in game engines

HI. I’m wanting to make a squash and stretch ball rig that I can animate in Maya and hopefully be able to take into a game engine when it’s done.

I thought I might be able to make one with a two or three joint rig but I’m not sure on how to approach controlling the squash and stretch.

Could anyone point me in a direction?

So far I have 3 joints: top, mid, bottom all skinned to a sphere. The joints are unparented from each other and the middle joint is suspended in the middle of the top and bottom joints using expressions.

I’m currently trying to make an expression to scale the middle joint inwards when the top and bottom joints are moved away from each other and coming up blank. Any help?

Can you try to be more specific about what you are stuck on, and/or show some sketches of the effect you are trying to get?

Judging from what you’ve said, with 3 skinned joints, you just need the ball to squash and stretch in one single direction? Does it not need to squash in any direction as the ball rotates? If it is just one simple direction, you could use anything like a blendshape, or driven keys, and just key the joint to the size and shape you want.

Are you specifically stuck on the syntax of an expression? Or the formula to preserve volume? Or finding a more complex way to squash in any arbitrary direction? Or…?

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