PDA

View Full Version : help with IK



jnddepew
06-18-2006, 03:09 PM
I'm new
I'm trying to do a short film but this character's IK isn't set up well apparently. when i move the foot null over and place it on the floor, it pops up and down and sometimes goes all the way through the floor (as seen in the picture)
does anyone have any suggestions of how to get his feet to stop doing this? :stumped:

t4d
06-18-2006, 07:01 PM
OK lw doesn't have the best IK BUT afew thing you have to work with in any apps is you have to pose the rig naturally

and that pic you have just ripped the hip way infront of the feet
I would changed that first

I've seen many cool rigs by other LW riggers as well as mine
and we all get IK Poppy if you pose the rig in a extreme way
eg- if you get elbow popping check the position of you shoulder
if you just knees poppy check the position of you hips

99.9% of the time this will fix the problem

OK if you need that type of pose for that toon

here are some other things to check


Make sure each bone only has ONE rotation channel controled by IK
if you need more rotation Split a bone make the extra split bone really small and then you can still only have one rotation channel control by IK and get a larger range of motion.

setup rotations limits ( not my fav method )

others may have other ideas these are the things i would try first

jnddepew
06-18-2006, 08:01 PM
the problem is that even when I don't have the character in an extreme stance, whenever I move on foot, the other foot starts jolting around and going up and down for no reason I know. :bangwall:

t4d
06-18-2006, 09:26 PM
the problem is that even when I don't have the character in an extreme stance, whenever I move on foot, the other foot starts jolting around and going up and down for no reason I know. :bangwall:

send it over here [email protected] and I'll have a look at it for you :thumbsup:

jnddepew
06-19-2006, 11:33 AM
thanks a lot. :D

jnddepew
06-21-2006, 03:07 PM
I sent the file did you get it?

t4d
06-21-2006, 10:22 PM
Ok Got the file Sorry it took so long I was working on a XSI rig ..

Now you have alot wrong things in that rig BUT I done the same mistakes so you really have done nothing wrong but learn afew things.:thumbsup:

I'll post here so if anyone else needs some help Hopefully this will help them too

OK

1/ Default pose ALWAYS keep the base pose ( the position you first rigged the character in ) IN the scene file, you can store it at frame -200 if frame 0 isnt' right for you if you had this pose in the scene I could pull it apart the rig and fix alot of issues seeing it's not there it makes it extremely hard to fix or even see where you have gone wrong.

Now tips i see you need to think about

1/ all ik joints need to be prebent at rigging stage
( eg - bend the knee about 5 or 10 deg's to tell LW which way the joint should bend ) this stops ALOT of Ik Wiggle

2/ Tidy up your scene hide any hold bones so it's easy for a third party to see what to select and key when posing the rig ( colours are also cool to uses )

3/ only have ONE rotation channel on each bone controled by IK if you need more rotation options for your character Spilt a bone and make the new bone REALLY small and then use that to give you that extra IK rotation control.
( This rule is the same in Messiah, XSI and most apps i think )
3D IK chain are a tricky thing to rig up

4/ Goal strenght keep it at around 100 if you find you need 10000 goal strenght you have other problems some where else.

5/ don't animate the mesh always have a null or a bone as your Main mover for the rig you do this so you can easily add parent nulls on top of other null to get more control
having the Mesh as you only controler doesn't giver you many options
( eg parent the mesh to a null and then animate the null ;)

for now i would re rig it and this time keep a default pose and keep inmind the aboive tips and if you need any more help email me again happy to give you a hand again :thumbsup:

check out out this rig and pull it apart and see how it works
http://www.thomas4d.com/T4D_Fred_Demo_Rig.zip

jnddepew
06-22-2006, 04:43 AM
thanks for the tips. i'll re-rig it and hopefully it will work better.:D

t4d
06-22-2006, 05:13 AM
sorry I could help you right out there
Just without a Default pose it takes time to rebuild the default pose
then to go on and edit it would be a major job sorry But happy if you send me your next rig =)

jnddepew
06-22-2006, 03:31 PM
well, it's a very simple character (only two legs and a head) so I just have to move everything back. When I try doing it with all yur tips, though it's a little bit better, the right foot still jerks around when I move the left foot and vice versa. What should I do?

t4d
06-22-2006, 06:03 PM
did you prebend the knee ?
How about Only one channel controled by IK ?

if you have done and still having trouble send it over I'll do it ASAP for you ;)