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Gabester
10-12-2005, 04:25 AM
Hi all,

I'd like to share a problem which has come up quite a while ago but I've not been able to get an answer for it, conserning rotational handles.

I need to rotate the hand controller for example for the character that I'm animating. I get strange rotations in my character when I use the rotate tool. I'm rotating towards the x axis, but I get rotations sometimes in both the x and y axis when I check the graph editor. This results in unpredictable results in the interpolation.

Does anyone else experience this? There is a workaround, to click the channel of the desired axis and rotate just in that, but even that causes problems because now the interpolation problem is fixed, but when I rotate through the channel control in the Y, the Z rotational handle doesn't tilt with it.

It's difficult to write down, but any help would be appreciated. If you require additional info please let me know.

Razr
10-12-2005, 05:44 AM
Check your rotation tool option, if you're in Local or World coordinates you'll get double interpolations. Set your tool to Gimble - forces you to rotate one axis at a time.

Dichotomy
10-12-2005, 04:43 PM
I get this quite a bit, becuase I work on a lot of technical animations and have to have screws screw in at different angles, so they need to be animated on one axis, but like you said, sometimes you rotate one axis, and get info on two or three. The best work around for this is to zero out your object, then group it to itself, rotate the group to the desired angle/position, then your objects rotation will be clean and it can rotate on the one axis.

what is happening is that world, and object, don't always have the same rotation axis/angles as the gimble (which is the objects true rotation angles, and they sometimes end up overlapping each other, ie. gimbleLock). So when you rotate the object with, say, world rotate, the program puts the object there and then figures out which axis get what to have it there, and that is usually an ugly, ugly, thing.
Hope this helps.
(if this isn't the best explanation, somebody correct me :thumbsup: )

Gabester
10-14-2005, 02:19 AM
Thanks for the replies guys.

Unfortunately razr that gimbal won't help. It's the exact same method as rotating with the middle mouse button via selecting the appropriate channels.

Create a primitive, then rotate it in the y-90 for example through using gimbal. You see what happens? The rotation X channel moves with it and you can no longer rotate the object towards the x axis. Whereas if you rotate it in the z angle, the other manips move along with it. It should be like that through every angle.

That's a good suggestion dichotomy but That means I would have to create new control objects to control my existing control objects just to be able to rotate it in the desired channels appropriately. Thats crazy talk. I'm animating a character and the less cluttered my controllers get the better. I have to maintain functionality after all.

Looks like there is no way out

G

Arcon
10-14-2005, 03:38 AM
Create a primitive, then rotate it in the y-90 for example through using gimbal. You see what happens? The rotation X channel moves with it and you can no longer rotate the object towards the x axis. Whereas if you rotate it in the z angle, the other manips move along with it. It should be like that through every angle.
G

as Dichotomy described, that's gimbal lock which is the basic drawback of using Euler rotations. Eular angles evaluate each channel independantly, and based on a rotation order. the ideal example you described is actually just local rotation mode, which is a bad idea for animation, it won't interpolate smoothly.

changing the prefs to quaternion rotation is an option to avoid gimbal, but i havn't animated with that method, AFAIK curves in the graph editor have to be represented as Euler's anyway, and the concept is easier to understand.

You can change the event in which gimbling occurs by selecting a different rotate order on the transform node. gimbal in biped characters normally isn't an issue except maybe in the shoulders (heh or the hips if you're character is a flexible gymnast/stripper). either try a different rotation order or a solution in some cases might be to have an extra node above the heirarchy that you can use for another channel, however you have to make sure your rig/blendshape workflow will work with that.

as for your specific problem what are you trying to do with the hand, just twist it...? you should be able to do that by animating just one channel, providing all the joints in your rig have an axis that always points directly down the bone (which all rigs should).

Craiger
10-14-2005, 04:35 AM
Check out my reply to this thread. It should clear up some things.



http://forums.cgsociety.org/showthread.php?p=2485941#post2485941


werd.

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