View Full Version : Question to Rebell Hill, Larry and Lw, Xsi and Maya Animators

02-03-2010, 04:40 AM
well, I animated a character these days on lightwave and it was too bad to use IK goals to keep the foot on floor. It "flicked" a lot, and sometimes I couldn't pose the character exactly where I want.

The distribution of forces in IK made the chain crazy and the Goal object was not kept in position althought his force was infinite. The IK chain and expressions are right, but much more Ik controls I have, more unstable the animation is.

The job was done, but it was a crazy amount of work. Just thought Ik should make life easier, but it didn't.

My questions are...

Does the same happen in Maya and XSI?
Is the IK in XSI and Maya better to work?
Is LW ik system similar to maya and Xsi in terms of stability?

Does LW have the basic tools to animate a character Maya and XSI has?

02-03-2010, 07:04 AM
I haven't had much in the way of problems keeping feet in place, can you share a scene with us to have a look at?

02-03-2010, 02:20 PM
I agree with Mike, I dont have problems making feet stick etc.
Make sure that you prebend the legs to let LWs IK solver know which direction the joint is supposed to bend. I also tend to use 2D IK...for example, on the thigh I use a small bone for the bank Ik (rotates the leg out to the side) and the thigh itself gets pitch IK (bends the leg forward and back). Typically this gives increases stability and extra control if I need it.
Ive found that using "keep goal within reach' sometimes can cause twitchiness.
You shouldnt have to use a large goal strength on normal sized characters. In the past LW did have issues (and probably still does) with characters with a very large or very small scale.
I would turn off any expressions and test the IK that way first to make sure its stable. Sometimes expressions might interfere with how the rig should be working. Make sure the basic aspects are working before adding more complexity on top. :)

02-11-2010, 07:40 AM
scene files attached.

Althought IK goals animation are LINEAR it still flics with the IK force.

02-11-2010, 10:12 AM
I'm not sure but bone 5 and 6 (shin bones) shouldn't have their heading controlled by IK. If you put them back to keyframes that solves the popping knees.
I didn't see any slipping feet in LEGS_AMIN.lws!

02-11-2010, 12:10 PM
Certain bones like elbows and knees should have iK in only one channel. Hips and shoulders are universal joints and y ou can eithere have IK applied to more then one channel or use two bones (each with IK in one channel) to create the universal joint.
Also remember to move the iK goals in arcs. Sometimes if the goal gets too close to the beginning of the iK chain it can cause popping issues etc.

02-11-2010, 01:47 PM
I haven't looked at your scenfiles yet, but here is what I can say:

I just recently created a rig for animatic purposes in LW, and had no issues at all with IK
(it is a quadroped rig). As Larry points out, it is good practise to force IK to only solve in 2D (one axis). I always make sure I have only one axis / bone that solves IK, which makes things so much more stable.

If I were you, I would follow Larrys suggestion to the point and make universal joints using two bones instead of one for the IK-solving.


02-12-2010, 08:44 AM
Yeah, as the others have pointed out, all thats wrong here is your use and setup of IK, to get a good 3d joint, like hip or shoulder, you need a twin bone setup to allow things to point where they need to be able to.

As you have it now is a single bone, working as a single layer, with multiple, or complex motions happening on it, its much better to use many layers, with each layer being much more simplistic and predictable.

Whilst some here recommend the 2 bone IK setup, with IK on different channels for each bone, I fond this still causes a bit of unpredictability, and still some popping, so I prefer the 2 bone solution where one uses targeting, and one uses IK, the same way that the "make joint chain" script sets things up.

So it all right, and there wont be anywhere you cant pose the IK controls, no pops, flips, stiffness, nothing

download my exapmple rig to see for yourself here;