Stars and Screen Mode Rendering

Screen mode rendering is now an option in the render code, allowing for the build up of color and light from the stars.  Unfortunately, the bright parts of the galaxy need a lower exposure level than the faint parts of the galaxy.  How to solve this?  Still under investigation... some tests below.

exp: 0.003, center pretty good

exp: 0.003, side view blown out

exp: 0.001, pretty dim

exp: 0.001, side view looks ok

exp: 0.1, major blow out, but faint areas are better