Problems with orient along path in 3d composition

[Bee24120249dzm6]

Hi all, 

I have a composition running geolayers 3 and want to do a simple 3d camera fly in and have some objects enter the screen along bezier paths. The problem I'm running into is with orient along paths, which is obviously orienting the objects along every axis, when I only want it to orient along the z axis. I could just adjust the orientation manually but it's not as smooth and somewhat impractical with the many dozens of objects that the scene will have. I was wondering if there is an expression that can be used to restrict the orientation to the z axis alone (all the other similar questions asked on here and elsewhere seem to refer to auto orient to camera.)

I have attached three videos to help illustrate the issue. The first is an overhead view of what is happening with auto orient turned on. The second is the camera movement with one auto oriented object entering along its path. The third is the same shot with auto orient turned off. 

Any help much appreciated. 

[Mylenium]

http://www.motionscript.com/design-guide/auto-orient-y-only.html

Mylenium

[Bee24120249dzm6]

 Hi Mylenium, 

Thanks for the response and thanks for all the other times you've helped me out by answering questions on here! 

I'm not usre if I've misunderstood the expression or the issue is that geolayers doesn't use a camera, it's a sort of pseudo 3d with an anchor null, but this expression applied to the z rotation of the layer doesn't fix the issue. 

I've attached a video of what is happening when I apply the expression to the z rotation and have auto orient turned on. 

Thanks again