Camera3D.screen not working as expected

[Sören Meyer-Eppler]

I'm beginning to lose my sanity over this. Could someone please take a
look at the attached minimal sample program and tell me what's going on
there?

What I am trying to archive is reproducing the perspective projection
the camera does in order to find the exact 2D bounds of a 3D object.

To test this I have generated a sphere of radius 100 at the origin and a
perspective lens camera at (0,0,-300). I then use Camera3D.screen and
Camera3D.lens.project to project a pair of test coordinates. I have
verified (by tracing the sphere's vertices) that these coordinates are
on the surface of the sphere. However, the screenVertices I get are not
on the 2D sphere silhouette as I would have expected. Am I using the
wrong matrix? The wrong approach?

Global stage scaling is off. I'm using the latest subversion revision of
Away3D (not lite).

best regards,

Sï¿œren