Fog bias -- what does it mean?

V-Ray V-Ray for 3ds Max General
1

I don’t see in the manual where the Vraymtl setting of Fog Bias is mentioned…

What does it do? What are reasonable values to use?

2

It changes the way that the object thickness interacts with the fog color to produce the final shading. Using this option allows you to make thinner parts of the object more transparent, while keeping thick parts the same, or vice versa. It is not a physically accurate effect and so it’s not easy to describe it in real-world terms, but it may be helpful if you are after a specific result.

Best regards,
Vlado

3

How do you control it? How does fog bias 0.0 compare to fog bias 1.0 at the same fog multiplier?

I’m experimentig with it but i cant get it to work,

4

1/fog multiplier=the distance, in generic units, at which the object will have the fog color as transparency.

Best regards,
Vlado

5

1 being fog bias (i asked for 1.0 particularly) in your equasion? I did notice that there was a drastic difference when i used -0.99 and -1.0.

6

I did a test last year about this paramater. It is one of my favorite spinner, but hard to fine tune.

Here were the results, feel free to comment : http://www.pixelab.be/blog/2008/09/14/fog-bias-parameter-test-in-vray-material/

Could be quick to do the test with RT now

7

@pailhead:

1/fogbias.

so 1/-1.0 = perfect 0 whereas 1/-0.99 = 0.01 wich might make a big difference depending on scene and scale i’d say.

Nice one Philippe! will have to take a closer look later on.

Regards,
Thorsten

8

cool info. love your blog btw. just downloaded the macpro maxfile and am bringing it into maya to mess around with, using the new vrayfor maya.

9

Isn’t 1/-1.0 = -1.0 ?