View Full Version : biped style rotations on regular bones

04 April 2003, 02:56 AM
hey all, does anyone know how to make biped style rotations on regular bones? what i've noticed is on a biped, you can select say the 3 segments of a finger, and rotate them all at once; each on their own axis. when i try this on regular bones, they just all go as if im only rotating the base parent bone. crapo. and when i turn off 'affect hierarchy' they all go their own way. craappo. does anyone know what makes the biped bones different and how i can convert the normal bones to use this handy linked rotation method? cheers :p

04 April 2003, 08:04 PM
Biped is a unique system within 3DS Max, it is not a 'dumb' IK rig and can do things that normal bones can not.

Now I have alot of experience with biped and not alot with wire params and standard rigging, so hopefully somebody will come along with a good answer - but if & untill then I can only suggest that you add a dummy to the end of the chain and see if FK will give you the flexibility you seek.



04 April 2003, 11:25 PM
If you're wanting to rotate the three joints of the finger (or any joints) like in the Biped, the easiest way would be to do it with wiring. Then you just select the base bone of the finger and rotate that and the others will curl nicely to follow.

So, you have your index finger, bone01 is the first joint, then bone02 and bone03, (where's Cheech when you need him?). Put a list controller in the rotation channel of each bone and assign an euler xyz controller to the available slot and make that controller active. Then just wire bone01's second controller rotation (say it's z axis) (and this is the active controller, the second one) to bone02's second controller rotation z axis. Then wire bone01's z axis again to bone03 and put /2 behind the expression in the wiring dialogue. The axis that the rotation will be around, normally either y or z, depends on which window you made your bones in.

You can control the amount of curl in the expression in the wiring dialogue. That's what the /2 is for. It cuts the rotation of that bone by half.

If you want to have more control and get very realistic motion of the fingers, assign reactor contollers the z channel (or y, depending) of the bones and let the rotation of bone01 drive the the other two bones based on bone01's angle at any given time.

If you need to have control over the bones individually again (i.e. without curling all at the same time) make the first controller active in each bone and you can do it. You could also wire all this up to a slider or Custom Attribute.

I know it's not a very good description, but if you understand wiring and the reactor controller, it should get you started. Sorry, if it's something simple that you already understand and I'm being redundant. But anyway, I think that's the easiest way to get that kind of motion out of a bone chain. And you only have to animate the first bone or a slider! Any specific questions, just ask.

Mahlon Bouldin

04 April 2003, 10:18 AM
thanks, yeah im aware of reactor controllers and wiring stuff together, but i was wondering if there was a way to convert the bones rotation system so that they acted like biped bones on a direct control level. ive been told that it works the same in maya; you can just rotate them all at once. i guess max is just 'stupid'. oh well. thanks :P

04 April 2003, 11:21 PM
max stupid? The wiring and controller way is much a more flexible and powerful approach. Do you see?

Mahlon Bouldin

04 April 2003, 12:05 PM
It's not tho... as the original poster mentioned he wanted to do it without wiring.

This is actually easier/more powerful because you can select only certain joints that you want interactively, vs. having something hard wired so that when you rotate the first joint or change an attribute they all go.

It's better to have it simply work where if you select 3 things, each rotates as you rotate...unlike max which only rotates teh parent. That way you as an animator can select only the first 2 joints instead of all 3 say, or every other one, etc...and it is just right in with the flow of regular select and rotate.

So essentially it is more dynamic that way. As he mentioned Maya works this way, but Max will figure out if the selected objects are part of some hierarchy/chain, and if so, only really affect the first one.

05 May 2003, 03:03 AM
I see your point. With Biped fingers, though, if I rotate the first joint and second joint backward together, the second joint rotates without a limit, and I have to compensate by selecting the second joint alone anyway, and rotating it back. (Curious if it works like this in Maya?)

But I see what you're saying for multiple rotation being more powerful as a characteristic of bones -- and the option to use it --rather than using wiring to accomplish it alone. I thought he was probably talking about finger rotations with CS, and that's an issue I've run into with multiple selected joints. Also, I hope you didn't think I was calling JeT 'stupid'. It was a question about the 'stupidity' label of max.


05 May 2003, 12:46 AM
'max is stupid' is the simple explanation as to why the bone system wont accomplish multiple rotations. I'm still seeking this result as bending towards FK I can accomplish desired character poses much faster with the biped style rotation. I've tryed turning off 'inherit parent rotation' as well. I guess 1 way to do it would be to build a bone system where at the end of bone 1 would be a dummy linked to it, and then bone 2 is position constrainted to the dummy, and then rotation constrainted maybe but that would probably interfere. Anyway I'm not prepared to do that; its far too much bother to do that for every bone on a character.

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