View Full Version : Harder than it needs to be?

10-20-2006, 07:59 AM
Ok, now that I have your attention. :D

I'm working on an animation of a vehicle that has different size wheels all resting on the ground and roatating at the same time. I want the wheels to all turn accurately to each other. I'm thinking there should be some specific mathematical formula here, but am I making it harder than it needs to be? Would it simply be a matter of figuring that one wheel is 82% the size of another, so I should just rotate the smaller wheel at 82% the rotation of the larger wheel?

Any suggestions on how to use an expression to do this? Haven't really gotten into figuring out that part of the program yet.

Thanks in advance.

10-20-2006, 09:51 AM
That would work. :)

10-20-2006, 09:53 AM
Okay, somebody feel free to double check me on this since I've not done it in a while.

If you've set the rotation for the bigger wheel (let's say) you can set a channel follower modifier for the smaller one on the same channel (i.e. pitch rotation). Set it to follow the pitch rotation of the larger wheel and set the appropriate scale.

For the scale of rotation: if you're setting the smaller one, you'd take the radius of the larger wheel devided by the radius of the smaller wheel. Then multiply that by 100 and that should give you the percentage the smaller needs to turn in comparrison to the larger one. I'm doing this real fast in my head so I could be wrong.

10-21-2006, 12:37 AM
Thanks. Had a feeling I was overthinking it.

10-21-2006, 03:09 AM
Or you can learn the expression by doing Richard Brak's tutorial,
and make the wheels spin at the right speed automatically by how fast the vehicle's moving

10-21-2006, 07:26 AM
Use Dodgy's plugin MGwheel it makes everything so easy.

10-21-2006, 04:03 PM
Dr Cycler or Dr Wheel Rotater are two parts of Relativity that would be useful as well :)

10-26-2006, 10:53 AM
Thanks for all the tips. I'll check them out.