CGTalk - IK for robotic leg

MCGrund

05-13-2003, 01:22 AM

Hi all,
the last couple of hours I've been trying to rig this robotic leg with IK.
I created goals for the tip and also for the two "knees". This causes some problems as the "knee-joints" start to rotate in other than the designated directions (arrows), because they try to reach their goals.
At first I tried it with SoftIK but this was way to wobbly. The standard IK seems to work better. The unwanted rotation isn't so bad anymore but it's still there.:annoyed:

Has anyone around a clue how to rig this kinda leg?
Thanks in advance.

http://public.rz.fh-wolfenbuettel.de/~grund/cgtalk/roboleg.jpg

JIII

05-13-2003, 03:04 AM

seems to me you need to restrict the rotation to one axis.

don't really know how to do this but it might be possible in xpresso.

heck you could set the forward motion to link into the rotation on one axis.

but then again my Xpresso knowledge isnt like mdme sadies, basicly its faulty

MCGrund

05-13-2003, 06:51 PM

Thanks for your reply JIII.
I also thought about restricting the rotation. But like you I got no clue (Oh, what a wonderful rhyme), and my Xpresso knowledge is...well...next topic please.
What do you mean by setting the forward motion to link into...? I don't really get it.
Maybe I should've mentioned that I'm pretty new to rigging.

pit

05-13-2003, 07:32 PM

This could come in handy:

http://www.mindthink.de/ohm/mechanics/download1.html

Cheers

MCGrund

05-13-2003, 07:48 PM

@pit:
Thanks for this link. The plug-in looks pretty interesting. I'll check it out.

JIII

05-14-2003, 03:46 AM

I was thinking of making a null object.

than creating an Xpression for the null.

the null object would export the data for the axis position for one of its axes(doesnt really matter which one) connect that to a rangemapper, which would then link into the object that you want to rotate. which would have an import port for just one axis of rotation.

that way you could move the null and the leg would move to.

I have not tried this out purely experemental, but it should work. if not play with it some then it might work.

flingster

05-14-2003, 01:49 PM

twisted-ankle: if you do use ohm mechanics plugin for anything please please post your results...would be very interested in how you got on:thumbsup:

flingster

05-14-2003, 04:52 PM

http://www.lachlan.clara.net/3d/tuts/xpresso/new/walkthroughe1-pi.html

always worth a read...maybe not for what you want..

MCGrund

05-15-2003, 10:46 PM

@JIII: Ah, now I know what you're talking about. Sounds like a good Idea. I also got some new ideas but haven't tried them yet. Maybe I'm going to test OHM Mechanics first I don't know yet.

@flingster: Yeah, I'll post results as soon as I get some. But as I'm parallely working on something else (though for the same project) it might well take some more days. Thanks for the link btw.

Stray

05-16-2003, 09:12 AM

Why not use a slider to rotate the objects position?

I was hoping that MOCCA would enable implicit control over an objects movement.

It is cool for floppy soggy things like tentacles, but for rigid mechanical things. I feel it doesn't cut the mustard....

Good Luck!
-Stray

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