View Full Version : need some help : expression

06 June 2003, 10:15 PM
i have this character rigged and all.

now,i made an ik for the arm,working fine.
what im trying to do , is wire the shoulder to clavicule (collar bone) so that when shoulder to maximum (i guess 90 degrees),collar bone starts moving.

anybody has a clue how to do this? i just learned a bit about wiring parameters with the tut from max,but dont know how to do my own stuff.



Aaron Moore
06 June 2003, 05:14 PM
You should be looking at IK/bone constraints rather then using expressions.

06 June 2003, 06:03 PM
No, expressions are perfectly valid here. "IK/bone constraints" (joint limits?) won't get you where you're trying to go.

I use two different methods for this sort of rig, each with some pros and cons. Both are too difficult for me to explain in words, though, so I'll see if I can get a file posted sometime this weekend, maybe with a mini-tutorial. I need to get off my arse and get my character rigging stuff together anyway, so this should help:)


06 June 2003, 09:15 AM
While I work on a more...ehmm...professional presentation, here's a file to play with. It's a simple IK arm illustrating one method for rigging an auto-shoulder. See the script controllers on the shoulder joint's Y and Z rotation channels to find out where the magic is happening.

Warning: there is as bit of math in there! If you understand vectors, the cross product, and transform matrices on at least a basic level, then you should be able to understand how it works. Otherwise, it will probably be a mystery until I have time to explain it better.

Here's the file! (
(ignore the missing plugin crap, and be aware that the production renderer will <probably> be listed as missing renderer. sorry!)

By playing with it a bit you should be able to see what the problems/limitations of this method are. I'm not sure if there is one "perfect method" in Max, but later on I'll demonstrate an alternative that works better in some cases (and worse in others).


06 June 2003, 02:07 PM
wow!! somebody actually replied:scream:

thank you LFShade!
i will try that scene right away.

about me understanding math,euh,hehe,i dont know too much,as im doing litterature and arts,my math knowledge isnt very expanded.

thanks again,ill post a reply soon :)

EDIT: it seems the file isnt there anymore.:shrug:

06 June 2003, 06:46 PM
I screwed up the link. Try again:thumbsup:


06 June 2003, 12:52 AM
wow dude!! thats looks so goooood!! exactly what i wanted.

but i really have no clue how you did it,i dont even know where to check the expressions you wrote to do this.
im rather new to this part (script/expressions) even after 2.5 years of maxing.

if you get sometime someday to get a small tut up....:scream: :buttrock:

please let me know :)

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