I did notice this new parameter since the 1.5 Service Pack 1, and decided to make some test. Actually, this parameter does exactly what I need… but it’s quite hard to explain and an image will be clearer than thousands of word :
Let’s say that it quickens the darkening of the fog inside the material, like if it become exponential when the bias is set below 0. If you lower the bias too much, it’ll darken too fast and you’ll have to lower the multiplier accordingly.
The good point of the test is that it doesn’t involve any glossiness nor transluency, the rendering times were relatively low and the shadows of the object just perfect ;)
Here are the results of the test, I did start with THIS base material
Ok, it’s completely black now. Let’s see if we can have something going to pitch balck but more progressively while dividing the multiplier by 10
It seems to work ! Some further test with more extreme values
And the last one goes from almost clear to completely balck without excessive variations of thickness. Once again, chaosgroup gave us here a tool to fine tune some incredibly useful materials. Fitting perfectly in the VRay pipeline ! Congrats ;)