Advanced eye rig problem

[pen-1]

I have an eye set up with the characters that I am working on where the eyes are not round. The eye has been grouped and the group has been scaled to get the desired shape. This means that the eye itself can still be rotated correctly.

My problem is a step past this. The group for the eye has also been rotate at an angle, this in itself isn't a problem because an Aim constraint works just fine on the eye. I however have to add another layer of control. The pupils for the eyes are closer to the middle of the head for design reasons and this causes the problem that when the character looks right the left pupil gets burried in the head before the right eye reachs the side of the eye socket.

To get around this. I have created two Locators, one has the aim constraint and the other an expression to control the amount of rotation based on the direction of rotation on the first. This works great but here is where I get stuck.

If I parent the eye to the expressioned locator the rotation of the eye is not directly related to the rotation of the expressioned locator because of the angle of the group that is on the eye. In other words if the target object move up and down the pupil on the eye rotates on an angle.

I have tried a constraint instead of parenting but that gave the same results. I am not familiar enough with MEL so I haven't been able to get worldMatrix to work in an expression. I don't even no if it will help. This this the right method? Is there another method to follow that will return the result that I am looking for?

Sorry for the long post

[gnimmel]

The easiest way to stop the eye from going too far would be to turn on limits in the rotation.

If you want to use a expression or SDK for any reason, it might work better comming from a dummy eye. Make a dummy that uses the aim constraint and then write the expressions to control your real eye by using the rotation of your dummy eye.

Richard

[pen-1]

I guess I wan't that clear. I am using a dummy eye. I have two locators, the first has the Aim con and the second is expressioned to it so that it rotates the way that I want. Limits in the rotation will not look natural as the pupil of one eye would stop moving before the pupil of the other.

The problem is when I constrain or parent the eye to the expression controled locator the eye is not rotating around the same axes as the locator. This is because the eye has a parent group that has been rotated and scaled to get the deformation on the eye that we want.

So the question is, how do I get the eye to rotate on the same axis?

[pen-1]

I think one possible solution is an expression that pulls the world rotation and not a parent rotation. My problem is I am fairly new to Maya and have yet to solve all the Mel and expression syntax methods.

I know that getAttr myObject.worldMAtrix (thanks to those who answered a post in Mel script) will return the world matrix of an object.

How can I pull the rotation part of the worldMatrix and apply it to another object.

Psuedo code...
myControlledObject.worldMatrix.rotation = myControllingObject.worldMatrix.rotation;

How can I do this?

[pen-1]

I still would have prefered to do this with an expression using the matrix (mostly because it sounds cool) but instead I redid the whole eye setup. Instead of using a group to scale the eyeball I use the method I always use in Max which is a lattice. This avoids the scale issues which then don't affect the rotation part of the matrix.