Squash and Stretch in Rigs

[pooby]

A lattice?

[Womball]

Would that be animateable and consistently deform a rig?

[jugger]

hm, if you consider this as an effect a lattice might be a nice thing. you would plot the animation of the mesh and apply the lattice later on.

if you want a rig that can do that, you need all elements (spine, legs, arms, head) to righ so that they can squash and stretch.
wether you use extra controls that you can move around to define the distance between the limbs or you use the controls you already might have.
you need couple expressions on the bones or the objects that are used for skinning to extend their axes up to the distances between the control objcets.
you can easily get these functions out of the expression editor menue. so its not too hard to do. for correct volumes you need to fracture in the width up to the lenght scale obviously.

colour coding is easy as well. just drive the colour in the shader of the bones with a linked key that reacts to the length of the bones.

3dquakers xsi pro rig got these features and its a good ressource. you might wanna have a look.

[Womball]

I do have that tutorial. However I don't want to use the entire rig, its a bit heavier than I would like. I want to combine aspects of the Digital Tutors rig as well, since the upper half is really simple and seems to get the basic across nicely.

What would those expressions look like?

[jugger]

might look complicated but isnt. most of the code is just copz&paste or is done by getting it from the expression menue.

"cond( ctr_dist( Trin.clavical_Eff_R.kine.global.pos, Trin.Hand_Control_R.kine.global.pos ) > 5.08, 2.48 + ( ctr_dist( Trin.clavical_Eff_R.kine.global.pos, Trin.Hand_Control_R.kine.global.pos ) - 5.08 ) * 0.5 * Trin.Hand_Control_R.Hand_Controls.Stretch,
2.48 )"

this example is form an arm chain. 5.08 is the length from the shoulder to the wrist and 2.48 is the length of the lower arm bone.

the cond(ition) is testing if the distance between the two points is bigger than the actual length of the bone (2.48).
if thats the case we need to stretch it (increase the length) to the actual length that is now between the two points, divided by two (*.5) to distribute half the stretch to the upper and hal of it to the lower arm bone.

the last number is the false condition and applies all the time the bones are not stretched.

voila :)

[Womball]

Thank you! Now how would you apply this code to the overall rig?

Should I use proxy geometry, my model is 4000 polys tops. It seems like if I went with the riggiing pro method, I would be spending a lot of time setting up proxy geometry skin bones. Could this be avoided?

And if I go with the digital tutors method, does this make sense this question:

Also in the rigging dvd, its confusingly covers parenting. It says to select the foot root, click parent, than click on the leg effector. However when I select the leg effector, the whole foot chain highlights. IN the DVD he than does this step where but he drags a box around the desired parent (the leg effector), and it parents it! When I tried dragging a box to select this effector to be the parent, it says action canceled. What am I supposded to press just to select the effector and nothing else?

I'm having trouble parenting.

Here's my character btw, blender renders of the cage. It will be subdivided once or twice in XSI.

http://img.photobucket.com/albums/v499/mayaman2/frontlowpolyview.jpg
http://img.photobucket.com/albums/v499/mayaman2/sidelowpolyview.jpg
http://img.photobucket.com/albums/v499/mayaman2/backlowpolyview.jpg

I'm refining his eyes right now, teeth/gums, tongue and throat sac (to block back lighting the throat). Another issue I'm running into is that the transpancy of the helmut is blocking lighting the skin. So I have this floating skin, and the rest is really dark.

[Womball]

Middleclick did the trick. Can I rotate the bone while i'm setting up the rig so that the bones align to the center of the limbs?

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