Creating procedural dirt in 3DS Max with Mental Ray

Creating the mask for the dirt

We now want to create the mask. We do this by adding the material we downloaded earlier. If you have installed it correctly, then there should be a shader named “Dirtmap”, located here:

Select a #4’th slot in material editor, add this there.
Drag it from there to slot#3 in your blend map (mask slot).
So, my slots now looks like this:

(From left to right: 1: Final shader, 2: clean shader, 3: dirtshader, 4: mask)
They are all instanced into the first material.
My complete blend material looks like this:

If I apply this material right now with no adjustments, then the render looks like this:

What we discovered is that the maps should be inverted.
You do this by swapping slot #1 and slot #2 in the blend map. After this is done the result is the following:

Now we are getting somewhere. Time to make it more detailed, and have it detect all edges. This is done in the dirtmap shader you have in the mask slot.

Its default settings:

Keep the settings not mentioned here at its defaults, change the following:

1. Turn off “M_Illuminvis”

2. set rayspread to 45

3. set samples to 128

4. set nearclip to 0.01

5. set vectorblend to 1

The resulting render after these tweaks: