Cartoon Eye Rig with Lattice

[DannyTheGamer]

So I'm trying to rig a cartoon eye (non-spherical). I created the sphere, deformed it with a lattice, and then added the aim constraint to make it look around. All good for now.

Then I tried moving the lattice around and: 

1. if I move only the lattice, the eye doesn't rotate accordingly to look at the aim circle

2. if I move both (by parenting the circle to the lattice for example), it seems like the eye goes through a double transformation, as seen in the image.

Is there a solution for this? Thanks in advance

[slimboJoe · Accepted solution]

Ah yes, the old lattice eye.  This is a similar set-up we used for the VeggieTales characters back in 1999.  The problem is that the lattice acts upon the SHAPE node of the eye, essentially changing the vertices.  The AIM constraint you have set up acts on the TRANSFORM node, which stays at the original location when you move the LATTICE itself.  Move your lattice and then pick the eye and you'll see the manipulator is not with the lattice.

So, you need to CLUSTER the whole eye first.  Make the cluster RELATIVE.  Then make your lattice.  Group your lattice and cluster together, don't just parent the cluster under the lattice.  Now it should work.  You still won't get the pupil to aim at the point when you deform the lattice, though.  That's a more advanced setup using projections and a bunch of math nodes, beyond the scope of this forum and my time.  The projection technique will let the pupil stay the same shape when the lattice changes shape, which may or may not be the desired look.  Right now the pupil will distort with the eye shape.

This is NOT the technique we used on the Veggie characters as we had a separate piece of geometry for the pupil. 

[DannyTheGamer]

It worked perfectly. Thanks a lot man! 

[slimboJoe]

No problem, glad to help.  Nice to answer real questions instead of the super noob "what is a sphere?" type questions.  Post some stuff when you finish.  Love to see what people are working on.

[DannyTheGamer]

Will do. Thanks again man!

[davidtorresmonteiro]

Hello Joe,

This was helpfull thanks!

I was having similar problems with my Lattice setup!