Head representation

[Kevin Godby]

Hello, everyone.

Has anyone else had any problems with the shader-based head
representation used by VR Juggler trunk/master?

Whenever I've used it (across various machines), the head is drawn
incorrectly and often occludes the view. The wand representation seems
okay, though.

Also, my laptop is running an older version of GLSL that doesn't
support inverse() being called on matrices. It would be nice if
Juggler could detect this and revert to using the non-shader-based
head and wand representations instead.

Thanks!

—Kevin Godby