Greeting,
I've been working on a cartoony eye rig and I'm having some issues…
Right now, I got my eyeball and iris/pupil separated and I want the iris to follow the eyeball without getting affected by the eyeball deformations.

At first I tryed to use a sticky constraint to move the iris on the eyeball, but noticed a problem when the eyeball is deformed and iris is moving, it actually follow too well the uv's and motion is following it too much, so it creates funky motion in extreme deformations…

Anyways, now I've started something else, I think it will work(see image below):

step1-I'm placing one point1 to the center of my eyeball one point2 moving around eyeball.

step2-Point1 normal is actually pointing at point2, and than point 1 is projected on the eyeball(using ray sop)…it works super well, point1 is following the eyeball surface and it's normal is always perpendiculary too it…

Step3-Now, only think left is to make my iris/pupil follow point1…how?
I've tryed to use a “origin()” expression, but iris doesn't follow point 1 at all…

Anyone got suggestions how to make my iris follow the point moving over my eyeball surface?

I joined the scene to the post as well.

Thanks very much!


It's not going to bad,

I just updated the scene, so my point follows better the eyeball surface normal. I use a transferattrib sop to so…since I'm not familiar yet with this sop, I was wondering if it my cause problem or it's a good idea…?

cheers!

a different technique is to use camera projection…

arctor
a different technique is to use camera projection…

Could you elaborate a bit more please?

arctor
a different technique is to use camera projection…

Could you elaborate a bit more please?

make a camera with orthographic projection, put it at the L (and R) points of your head rig, have them project a texture of the iris/pupil onto the geometry of the eyeball…no need for a geometry iris/pupil.

it's not a perfect setup but your iris/pupil will stay a fixed shape…

Oh ok, I wasn't sure if that's what you meant. Actually, that's in my plans to finish up the setup with a texture projection. But, I'd like to be able to move my texture projection around on the eyeball surface and have it follow the surface. with this setup…

Right now my setup it's just the a proof of concept, + it can be handy to have real geometry guide(non-rendering) for animating…

Ever tryed such a setup?

yeah…
you can do a geo eye - for the animators to see - by just parenting a cone onto the centre point of the eye…
you can move the projection on the eye with the camera controls…

all the characters in the PBS show Super Why ( http://pbskids.org/superwhy/ [pbskids.org] ) were done this way…after weeks of hair pulling…

After weeks of hair pulling? really? It sounds so simple. And it actually makes sense, I was wondering if I should have the pupil auto orienting to the eyeball normal, which my setup was about…but maybe not…there will be some cases where I'll don't want them to follow the normal properly anyway…

hmm… interesting…

I actually found the solution to my problem using the Rivet constraint…