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View Full Version : Flipless IK in 9.6!!



jay3d
02-28-2009, 03:35 PM
Hi,

I've found a way of rigging that it results in FLIPLESS IK in Joint bones :D

BTW, snapping in layout is amazing!

http://img15.imageshack.us/img15/6065/flipless.gif

Cageman
02-28-2009, 03:37 PM
Great!

:thumbsup:

jasonwestmas
02-28-2009, 03:53 PM
If only I could do that with my legs ;)

UnCommonGrafx
02-28-2009, 04:02 PM
Pretty cool.
How?

RebelHill
02-28-2009, 04:20 PM
yeah... thats 2d IK... lets see u do it on a 3d joint, lol

jayroth
02-28-2009, 04:52 PM
yeah... thats 2d IK... lets see u do it on a 3d joint, lol

As you likely know, Rebel Hill, you rarely want to use "3D IK" to solve, as it adds an order of magnitude to the possible solutions available to the solver. The symptoms of that are:

Slower interaction speed
Non-repeatable solutions

In effect, these symptoms tend to render 3D IK rather useless. So, best to keep the solvers limited to 2D solutions.

The pole vector null gives you control over the chain orientation to a degree, though you would likely be better served by adding a null above the chain, limited to the axis not served by the IK solver.

geothefaust
02-28-2009, 05:10 PM
I just throw an extra bone in to serve each rotational axis of control that I would need (as learned from the masters!), so it still wont pop. :thumbsup:

SplineGod
02-28-2009, 05:46 PM
Actually getting flipless IK has been possible in LW for a long time using 2d IK. Its pretty much the way Ive always rigged in LW to get stable IK.
Before pole vectors were introduced I would typically use relativity etc to get the same functionality.

I dont think IK in LW was so bad. What would have been nicer would to have seen better animation management tools along the lines of what we see in IKBoost like keyframe modes, copy/save/load poses and motion clips as well as the ability to copy poses and motion clips directly between rigs.

Castius
02-28-2009, 09:20 PM
Ya the 2D part has always been pretty good. It's when you needed something more that you had trouble. Most animators want control over where the knee points. Otherwise they get cranky :)

Even if things didn't go as far as i wanted.
The changes to 9.6 have made it possible to do so many new things.

daforum
03-01-2009, 05:05 AM
Is there a tutorial available or could someone post one on how to do this. I'd be very interested in learning how to eliminate the "pop"

jay3d
03-01-2009, 05:53 AM
Is there a tutorial available or could someone post one on how to do this. I'd be very interested in learning how to eliminate the "pop"

Ok sir :thumbsup: , stand by :)

SplineGod
03-01-2009, 05:53 AM
The rigging videos I have on my site and thru KURV cover all this in great detail. For this particular thing you use two bones in the hip, One bone points down the z axis and gets IK in the bank channel only which allows the leg to rotate out to the side. The other bone is the thigh and gets IK in the pitch channel only. Other then that make sure theres some prebend in the knee joint. Ive found that those two things generally will keep things from popping most of the time.

jay3d
03-01-2009, 11:42 AM
Here u go:

Castius
03-01-2009, 02:54 PM
Good little walk through Jay3d.

I would do your pre-bend on frame -1 though. This way you can leave frame 0 for your rest pose. This works because LW defaults to reading the first keyframe for it's IK calculations.

daforum
03-02-2009, 05:17 AM
Thanks for doing this. I guess to stiop the pop on left/right movement in the x axis limits would have to be set in the same way.

It would be good if we could envelope IK limits, or is that the same as IK/ FK blending?

SplineGod
03-02-2009, 07:10 AM
My experience has been that using limits to try and fix popping issues only ends up creating a rig that is unstable. Its better to make the rig as stable as possible with few constraints before moving on.
IK limits and IK/FK blending are different things.

jasonwestmas
03-02-2009, 07:11 AM
Thanks for doing this. I guess to stiop the pop on left/right movement in the x axis limits would have to be set in the same way.

It would be good if we could envelope IK limits, or is that the same as IK/ FK blending?

You can create rotational and transitional limits on the bones if that's what you mean, so that the IK cannot move the bones past a certain limit.

Castius
03-02-2009, 09:53 AM
He wants to envelope those limits.

I agree with Larry don't put limits until the IK is working properly. It can trick you into thinking it working. Generally in the end you won't need the limits anyway.

daforum that legs can't move left or right. That's the point of 2D IK. It has no left or right. In the past i would say. You can't make a prebend angle in two different directions. But that statement would be wrong in LW 9.6. Because you can now set IK to "Base on Most Recent Keyframe". So you could animate the the underliying bones to drive how the IK should bend. BUT! this is not how i would want an animator to use a rig. It's a life saving feature but not a good standard method for a limb like an arm or leg.

Constructing a pole vector with a 2D IK on top of it is the standard workflow. It gives you a simple way to define where the 2D IK should be in 3D Space.

geothefaust
03-05-2009, 03:14 AM
Hey all,

I'm curious, can't bust open layout at the moment or I'd just test it myself... But does anyone know off the top of their head what the minimum pre-bend would need to be for the IK solver to function correctly with no popping? I usually just make the pre-bend pretty big so I can avoid any popping, but with the rig I've been working on lately I can't quite bend it so much without it messing around with some other stuff.

Anyone?

Thanks!

EDIT: I forgot to point out that I do have a pole set up, but still getting popping. Also, I'm using joints if that matters at all.

jasonwestmas
03-05-2009, 08:36 AM
Hey all,

I'm curious, can't bust open layout at the moment or I'd just test it myself... But does anyone know off the top of their head what the minimum pre-bend would need to be for the IK solver to function correctly with no popping? I usually just make the pre-bend pretty big so I can avoid any popping, but with the rig I've been working on lately I can't quite bend it so much without it messing around with some other stuff.

Anyone?

Thanks!

EDIT: I forgot to point out that I do have a pole set up, but still getting popping. Also, I'm using joints if that matters at all.


The only thing I can think of so far is that you may want to check your IK Axis in the motion panel and make sure you have "Unaffected By IK of Descendants" on the right joints. I usually have the most problems identifying the rotations themselves and which way the axis are pointing. If they aren't pointing in the right way the IK is pretty useless. I usually can get by if I create all the joints in one viewport perspective rather than two different perspectives, that way they are all pretty much in line the way you want. Also knowing which joint to use the record pivot rotation on is sometimes a pain too.

Castius
03-05-2009, 11:34 AM
I'd say between 5-7 or more is good enough.

If you using joints make sure they are aligned correctly. An easy way to tell is to look at the position. So for example if you select the shin joint. It should only have one value in the position. It's usually the z axis. Something like (0,0,1). For a more visual test you can convert them to bones temporarily.

geothefaust
03-05-2009, 01:42 PM
Hi Jason,

I always tick 'unaffected by IK of descendants' first! :) It can be a pain otherwise.

Hey again Scott, thanks for that. Exactly what I was digging for! Thank you sir once again for you invaluable help! Cookies are still on the table if you're interested. ;)

geothefaust
03-05-2009, 10:21 PM
A little update...

I checked everything. I made sure all was how it was supposed to be, and still, I was getting the popping. My pre-bend was just fine, I couldn't figure out what it was. I got it singled out to my pole vector bone in the end. Looks like somehow the target for the pole bone was removed. DOH!

All is well.

jasonwestmas
03-06-2009, 07:21 AM
A little update...

I checked everything. I made sure all was how it was supposed to be, and still, I was getting the popping. My pre-bend was just fine, I couldn't figure out what it was. I got it singled out to my pole vector bone in the end. Looks like somehow the target for the pole bone was removed. DOH!

All is well.

Yeah some how my pole vector null got removed once, I couldn't figure it out till I noticed it wasn't selected in the motion panel, DOH!:yingyang:

geothefaust
03-08-2009, 03:38 PM
Yeah, It's happened to my twice now and I can't figure out why or how, or even how to reproduce it so I can submit it as a bug. Something sure is fishy there though. Odd thing to happen... Glad I'm not the only one that has experienced it, I thought maybe I was going insane or had done something wrong.