Thank you, your explanation of the bright and dark parts within the image has made it clear, and I now understand what you are saying.
I tried your suggestion with the 3D glasses...looked at a 3D image that had the proper 3D effect, then turned the glasses upside down and the effect was gone.
Then I tried viewing Tomb Raider in Glidos with the glasses on as normal and the 3D effect was now working. So I didn't try Glidos with the glasses upside down, but was looking for what was different when I was unable to see the 3D effect.
I am playing on a laptop and the LCD wide-screen has sometimes been a bit darker on the right half of the screen...however at the moment while Glidos and 3D are working, the screen is normal and plenty bright.
So for now I will assume LCD screen malfunction was causing the viewing problem. (I thought I should have compared the game on my system with a CRT monitor, and now I wish I had before reporting a problem)
Thanks for developing this 3D effect for Glidos, it really adds a new dimension to playing the Tomb Raider game 😀