[vtkusers] Keeping an icon facing the camera

[Jeff Marker]

Good day all,

I've been using VTK for a little while now, but have seemingly hit a
wall; I'd like to display, in effect, an icon on screen that is always
facing the camera, no matter where it is in the scene. However, I also
need to be able to place it in world coordinates (so it can match
position with other objects in the scene that won't be constrained
with the camera).

I've been trying to work with mapping a texture to a vtkPlaneSource
object. I initially tried to use the vtkFollower actor; however, when
the plane source was mapped to this actor, the coordinates and
transforms seemed to be in a coordinate system relative to the camera,
which is something I really didn't want. I've also tried simply
calling SetNormal on the plane source to face the camera, however I
find that when the camera is at an elevation of say 45 degrees, and I
perform sequential azimuth adjustments, the texture slowly rotates
along the normal (eventually resulting in an upside-down icon that
faces the camera).

Any suggestions would be appreciated, thanks!

-- Jeff Marker
 jffmarker at gmail.com