Hi! Here's a simple question:
Is there any equivalent of the Maya's graph editor euler filter in houdini's channel editor?
What's seems to be close is using qlinear(), but it doesn't seem so flexible. For instance, it seems hard to make smooth in and smooth out using de qlinear()…it's linear…anything like qbezier()?

thanks!

I don't understand something here…

From the Maya 2011 on-line docs:

Euler angle filtering

When you import motion capture data into Maya as animation curves, the curves might be mangled when the rotation values are restricted to a specific range. You can filter the curves to correct the mangling.

Euler angles calculate the rotation interpolation using three separate vectors: the X, Y, and Z axes.

In the Graph Editor, select the mangled animation curves (for example, Rotate X, Y, and Z), then select Curves > Euler Filter. The filtering is always applied to entire curves, not to selected curve segments within some time range.

So this is used to correct the instantaneous euler flips in mocap data. Sure you can do that. In CHOPs, bring in euler rotation channels that have discontinuities and apply the Transform CHOP. Now you see that the rotation values are continuous and look perdy although functionally they are the same but empirically they aren't.

I can't see how one could actually keyframe those euler rotation discontinuities. I haven't run in to that yet. Is there a case where you are able to generate that? Most animators key right through 360 and beyond in a continuous fashion.

You will not get in to euler trouble if you use the Houdini rotation handles in default mode (not separated in to eulers via the preferences). I would also argue that any rig that gets you in to euler gimbal lock is a poor rig imho.

i think jrgauthier is talking about quaternion rotations more than euler filter
at least i was looking for it once and found only qlinear() function

jeff
…
I would also argue that any rig that gets you in to euler gimbal lock is a poor rig imho.
…

i have also done several poor rigs myself
and i can tell that it is really nice to have quaternion rotations for shoulders and similar problematic areas
quaternions in other applications have TCB (tension, continuity, bias) values for each keyframe allowing user to control the motion between keyframes
qlinear() in houdini just blends linearly from one keyframe to another

That makes sense and yes is a good RFE.

Hi Guys! thanks for your interest on the subject. I don't know if I'm talking about quaternion rotation, but here are more details:

It's the first time I actually see the maya document description heheh.
However, we(animators) don't use necessarily euler filter for mocap correction.

Maybe I need to be more specific here.

First, we have to agree that gimbal locks are a common thing animators will face animating rotations. No matter the quality of the rig or software.

For exemple, I just did some test with the Houdini Cartoon character rig and like any other rigs you can encounter gimbal locks rotatings arms or wrist for exemple. To me it's not the sign of a bad rig; no matter what rotation order you will use, sooner or later you'll get a gimbal lock if the motion you animate becomes a bit complex.


The moment you get into gimbal lock and you need to do a specific motion that your gimbal rotation axis won't allow you…you're kind of screwed.

On the other hand if you're using local rotation axis you can rotate your wrist(for exemple) freely in the pose of your choice. But when you play your animation, you can see that something is wrong, your wrist does “backflips” between your gimbal locked pose and your new pose…what do you do in that case?

You simply select your curves and press the “euler filter” button and voilà! It's fixed, your rotation looks fine and smooth.

You can keep on animating as no incident happened!

On the other hand, if you don't have the “euler filter” button, what can be done? Painfully untangling gimbal locked rotation axis and try to make it work?

I wonder if my explainations make sense or maybe I would need more graphic exemples?

In the meantime, I'll check out if I'm using rotations in default mode you're talking about, maybe it's the solution I need. Houdini is always full of cool surprises.

Cheers! Hope we can solve this problem!

Yep I get all that. I would still argue that getting in to gimbal like that is a rig issue but that's just me.
Gimbal in a writst control? That's definitely a rig issue imho. If this is in the toon rig, submit the bug.

RFE stands and now it's properly explained for R&D. All good stuff.

Thanks Jeff!

Hi , sorry if i'm rehashing old topics but i feel this one is important for animators.

You will get gimbal lock problems without even using a rig… rotations on a simple cube will do the same thing. You will start to find limitations with your rotations - crazy twisting/flipping.
So i dont think its really just a rig problem.

I know there are ways to include extra objects into your rig so that when you encounter a problem, you switch to those objects. I've used this method myself.

But Maya/Softimage has a cool little feature : *Euler Filter*
If I have animated characters that flip and twist at the same time, I will get gimbal lock( crazy twisting/flipping) on playback.
But if I just click that button in the graph editor/euler filter, it fixes the mangled twisting for me. I havent had to worry about gimbal lock 99% of the time.
It also saves time with rigging and trying to manage an extra set of rotation keyframes for those extra gimbal controls.

It seems Maya/Softimage looks at the surrounding keyframes/rotations, and finds the most logical rotation path , then adjusts the rotation curve accordingly. Its like magic , no more crazy twisting/flipping.

maybe Houdini has this now, i have tried to look for it but cant seem to find anything on it.

cheers nito

CHOPs can but that will convert channels to raw.

If you use the standard tumble ball while manipulating rotates in the viewport, you will not get in to gimbal lock.

Please submit the RFE (Request For Enhancement) to support. I can see how this could be handy for simple animation.

ok, will do.
thanks jeff 8)