Positioned spot light - white light appearing from nowhere behind
Hi. I am having a problem with a spot light positioned within a scene. The beam is constrained to an angle and projects forwards from the source in the expected way, however all objects behind the source are illuminated with saturated white light which seems to come from nowhere. The attached image and code demonstrate the problem in a simple chequerboard scene using a red light source positioned in the middle of the central globe, pointing to the right with a beam cone angle of 45 degrees. When the red light is switched off the white saturation also disappears. The additional diffuse light is just there to allow the scene to be observed more easily and does not change the problem symptoms.
I've not found any reference to this effect on the web, so could it be a Fedora implementation bug ?. I'm not able to test on any other OS.
FYI: My platform is Fedora 17 Linux. I have tested this on a number of different machines with different graphics hardware.
Any thoughts / suggestions most appreciated.