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Maximus_5610
03-08-2007, 12:54 AM
Hey people,

Im currently modelling a basic office chair for a uni project but I'm also considering rigging it up for animation. Just some basic stuff so it can slide along the floor and tilt.

http://members.iinet.net.au/%7Emattysmith/chair.jpg

I just cant seem to think of a way to setup the wheels so they will rotate and roll in the direction the chair is moving.....

If anyone has any idea it would be much appreciated.

Thanks !!

futurcraft
03-08-2007, 08:39 AM
I have a suggestion for you...

the easiest way for you to set this up would be with the help of a locator as a helper control & a combination of aim constraints.

you need to first setup the main chair direction. The way I look at it, the topmost section of the hierarchy could be the chair seat.

you will need a broken hierarchy for the wheels as such. Individual pairs of joints for each of the wheels, all aim constrained to the locator which is orient constrained to the main control of the chair.

while putting the hierarchy together, make sure that you avoid double transforms by grouping the rig elements under appropriate nodes..

Hope that helps...

Maximus_5610
03-09-2007, 01:37 AM
Hey thanks for the reply!

Had a crack at doing it using your suggestion but couldn't really grasp it. Had a bit of a play this morning using a different approach.

I created a locator and wrote an expression that drove its movement based on the velocity of a dummy passive rigid body (which I would constrain to the "chair controller"). I used aim constraints to get the wheels to follow the locator.

http://members.iinet.net.au/~mattysmith/wheels.mov (http://members.iinet.net.au/%7Emattysmith/wheels.mov)


Bit stoopid but was all my simple student mind could think of - the expression only evaluates during playback so it isn't interactive in the viewport (something i wanted).

Any further ideas or approaches would be awesome.

Thanks

ManuelM
03-09-2007, 01:48 AM
you'll propably spend more time rigging that thing and driving it by expressions or rigid bodies, than you would, if you hand-animated those wheels.
anyway, i think the first suggestions already made sense, so i'd try that and if you get stuck at a certain point, post the scene here and i'm sure you'll get help

Maximus_5610
03-09-2007, 05:22 AM
If someone can take some time to setup futurecraft's method so I can get my head around it it would be much appreciated.

SCENE FILE (http://members.iinet.net.au/%7Emattysmith/chair_test.mb)


Thanks

futurcraft
03-22-2007, 07:52 AM
When you are learning as a student... try to avoid delving into automated simulations like rigid bodies... this is just a personal opinion.. rigid bodies are quite robust but it takes quite a while to simulate & control its predictability... instead you can spend the same amount of time learning to actually rig up the chair and enable ur mind to solve problems... agreed, animating the wheels manually is the quickest solution.. but if you wanna learn the process of rigging, then I suggest, all you need to do is sit down n break the problem down into multiple simpler problems and then tackle them one by one... You will be amazed yourself as to how you were able to solve the whole issue as a whole...

Good Luck with your learning endeavours....

arcsecond
03-23-2007, 12:20 AM
I did something like this once. I found a faceForeward.mel script online somewhere that used aim-constrained locators and an expression to point an object toward it's position on the previous frame. I believe it originally came from a flocking simulation script. I ripped out the X and Z portions and it made pretty good swivel wheels.

Normally I'm not a fan of expressions as they tend to slow things down and are often not interactive. This one was small and I don't think the situation needs to be interactive.

Hope this helps.

-James

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