Car rigging - Tire squash and wheel turning?

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  11 November 2012
Car rigging - Tire squash and wheel turning?

In my current TD course, I'm running a bit ahead of the class speed. We're tasked with rigging a car, and I've got all the basics down, and I only have the tire squash and the actual driving of the tires left to do.

As for the squash, it needn't be physically correct, but something that updates in real-time (i.e. not utilizing any simulation). Basically, when the tire hits a certain height (or depth, as it were), it should squash a bit. This should also be working together with tires that spins (i.e. not utilizing a blend shape). How to set this up?

Secondly is the rotating of the tires when the car moves. I know the basics, how to get the tires to spin proportionally to the movement of the car when it moves in a straight forward line, but what's a good way to set up the rotation of the wheels when it comes to turning the car?

I know that it needs two pivots, one for turning left and one for turning right, positioned at the back wheels. I'm guessing this is achieved by grouping the master controller twice, and having each group control one turning direction. But how do I set up an expression that allows for the realistic and variational rotation of the wheels when the turning happens?

Edit: I've been testing out possible solutions for the wheel turning. Calculating the rotation is no problem, but the turning of the car seems to be a harder nut to crack. I can't figure out how to fix the dependencies without ending up with nasty compound motions. The turning pivot objects need to be parented to the Master Controller, so that they stick to it when it moves. Meanwhile their Y rotations need to control the Y rotation of the Master Controller, and everything parented under it. Ugh, this really gives me a headache :(

Last edited by hellspawned : 11 November 2012 at 12:59 PM.
  11 November 2012
for the tire deformation I suggest you look at lattices. You can have it applied to a skinned mesh and deform as you'll need.

For the turning, im not quite sure what you mean. I think perhaps you might be over-complicating it. I think what your after would require a follow expression and have the rear axis following the front? If that makes sense?
Alternatively you can look into motion paths.
  11 November 2012
Have a look at this,
You would end up in wheels spinning in opp direction if the global control is rotated more than 90 degrees. Its upon the math in quadrants.
Download Vehicle Rig
  11 November 2012
Thanks for the tip shinyprem! However, it doesn't really suit my needs, as this is a class where we are to learn how to build a complete rig from the ground up. It would kind of defeat the purpose of the class if I were to use a script for it :P

Idunham, how would I go about setting this lattice up, so that it deforms only when the wheels touches the ground? I mean, the deformer itself is easy enough to handle, but how do I automate it's function?
  11 November 2012
Well i would say the opposite if you learn what the script do and how it works.

I did create a car rig were it worked perfectly with a script that read the position from the previous frame when you translated the car in x and z and rotated it whatever way you wanted. i never got it working in the y axis thou to get the exakt rotation of the wheels if the car went up or downhill.
Voxels for dinner.
_____________ maya vfx blog
  11 November 2012
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