Many users have noted unexpected results when using the RPC Environment with a Mental Ray Daylight System. This is primarily because of the way that Mental Ray blends colors. There is a large sky texture that is some shade of blue and a ground plane that is brown or green. The effect of the blending of these two becomes a murky brown/green where blue should be. Through a little trial and error I have created a settings formula that works nicely with most scene configurations.
When the RPC Environment is added to a scene with a Mental Ray Daylight System it will render something like this:
This looks nothing at all like the rendering results with the scanline rendering. I will show you how to fix this.
We will start by changing the Physical Scale values under the Environment and Effects panel. I have changed from Physical Units to Unitless and changed the value from 1500 to 90,000.
This gives us the following results:
There isn’t much change shown, but when we make the next modification it will be apparent. Go into the RPC Mass Edit Dialog and change the Self-Illumination value from 0 to 55.
Now the RPC Environment’s color will render much better.
Finally the sky looks more blue than green. To make it look even better I will brighten the scene by boosting the exposure value from 15 to 14 (lower values increase brightness). This will give us a rendering that looks like this:
Utilize the exposure controls to tweak your rendering even further.
I hope this tip helps and good luck with your next rendering.