Character Rigging

[TheUsualAlex]

Howdy folks,

Anyway, while on the topic of character rigging from the previous post, I am rather curious.

For those of you who have rigged a fairly realistic character (or cartoony one as well) in Houdini, Maya, or Soft, what kind of deformation method do you consider as your choicest rig that would preserve the character's volume and muscle structure? In other word, if someone where to give you a photoreal character, what approach would you take?

Please feel free to talk about it from Houdini, Maya, or Soft set up.

Anyhow, my current favorite is what I called "Conditional Blendshape" in Houdini (or "Set Driven Key Blendshape" in Maya.) Basically, I am using a bunch of conditional statement to control the blendshape for the deformation based on the bone's rotation angle. I'll probably write up a tutorial on this for the Houdini community once I have put this method to full test in Houdini later on this month or early next month. But for now, I am hoping that this discussion will eventually lead to something interesting and unique to Houdini's set up. May be a CHOPs method or something. Or may be someone from SideFX will read this and get inspired to come up with something totally awesome. Who knows.

Cheers, Everyone.

ALex

[plan9]

hail bone daddy,

hmm interesting alex, would be cool to see what you have so far with your setup madness

i have done next to no setup in houdini, although i will be tackling it shortly. most likely ill be using setup methods learned while using maya.

lub

mike c.

[TheUsualAlex]

Good grief. No one else have any ideas to throw around?

Miguel? You have a good one, right?

Hey there, Mike, actually the Conditional Blendshape set up is nothing earth shattering to be honest. It was suggested by one of my good Maya friend here. I simply translate it into Houdini approach. It's still is a little bit tricky to deal with, tho, but it's not nearly as difficult as solving a visual effect problems (which is something I am learning still). However, this approach won't allow you as much "automated" deformation - you'd basically have to model your own deformation. Hence, you have full control over your model topology.

Peace, everyone.

ALex

[miguel m]

Alex, I don't have much to offer in this regard, snif...

Alex's approach seems well working and has nothing to envy in functionality to what you can do in soft3d or maya. I've been thinking on some chops solution. Since we're in houdini the norm is to always ask for something else than the others can offer right? well

One question , do you think the deformations should happen interactively as one bends and moves around the character or they should cook only after the character has been animated and then be able to tweak how those deformations happen?

I've thought about some interesting goals...

- should be easy to activate-deactivate those deformations for interactive speed.

- should not be tied to an expression that you'd have to retype to change behavior, but instead being able to blend behaviors as the animation evolves.

- if the deformations are linked to bone rotations in some way one should be able to control the "linearity" of the relation, not just a morph from one shape to the other as the bone goes from an angle to the other.

Sorry, I'm sounding too esoteric and not concrete at all. Alex, see what happens when you ask someone who doesn't know the tools? hehe. I'm interested as well as Alex in stuff you have developed, thought or have interest in seeing... I'd ask anyone to throw whatever comes to his/her mind and maybe we could bould build an interesting thread at least with goals-tips-whaterver.

[TheUsualAlex]

A long while back Jason was mentioning about querying Point Weight (in VEX, of course) for character rigging or something(?). What I don't really understand is how to utilize point weight to rig a character...

[TheUsualAlex]

Anyone else have anything to add here...?

[thekenny]

here's one thing to add.

i've found if you are used to using positional constraints in soft3D to break up the skeleton heirarchy so you don't fall victim of children taking on the parent's rotaion.

you can use the BlendOP to mimic that kind of workflow. by using the txtytz only of the immediate parent and using the second input of the BlendOP to use the rotations of a master null at the top of the chain. it works out well.

there are a few cons. the cooking of the network is a bit heavier with the BlendOPs. if you don't get the second input right you end up with either no rotaions or incorrect ones. you might have to play a bit with the correct location of the blendOP to get it at the end of the bone. if you look at the expression in the second bone in a two bone chain you can use it to get your blendOP at the end of the bone in question. it will follow the length of the bone so if you are doing any wacky scales or adjustments it is okay.

hows that?

want more...

-k

[betty]

to thekenny

re;

hows that?

great stuff

and

want more...

give us all ya got!!

this is really nourishing as i'm in the middle of learning how to do character animation in houdini.

and miguel the idea of having the deformations come from another source other than the bone rotations sounds quite practical, i suppose this way you can vary the effect from when a guy is lifting up his arm to light a cigar comapared to lifting something heavy .

[TheUsualAlex]

I just thought about something...

Previously I stated "Conditional Blendshape" using whole bunch of If-Else expression. May be that's not even needed at all in Houdini. I think CHOP might be able to do it to drive the blendshape for deformation.

Not sure.

[danteA]

and miguel the idea of having the deformations come from another source other than the bone rotations sounds quite practical, i suppose this way you can vary the effect from when a guy is lifting up his arm to light a cigar comapared to lifting something heavy .

Jason mentioned a technique earlier that I've found quite cool. What you do is find your pose and use the sculpt sop to get the deformation you want. You then take the input into your deform sop and pipe it into the sculpt sop in the network editor. After that you blend (sop) the input with your sculpt sop and output into your deform sop. In the blend sop, you use a boneangle expression to give the desired interpolation as you animate your joint. Now, this boneangle expression can easily take into account other channels (eg. heaviness) or even be driven by chops as well.

here's a contrived example of what I meant:

capture -----------> sculpt---\
      |                                    > blend ---> deform
      |----------------------------/

dante

[thekenny]

true enough, the SequenceBlendSop is actually very good at this.

with enough understanding of what kind of action you require you can use the fit expression to easily convert crazy results of the bone angle expression. just model your changes and adjustments and plug them in the correct order.

the bone angle expression is not just for bones either. you can add a null to your character network in object space and use it for a better bone angle results.

i've done stuff with deforming mesh before it is even captured to get better sublte animation. it takes more SOPs and some effort. at times you will have something so complex and heavy you will never be able to see it in real time.

-k

[TheUsualAlex]

Neat!

That sounds like pretty much what I have in mind. Except that I was doing the blendshape after the Deform SOP, tho.