Dirt maps

firewolf

Here's a question...

I'm using 3ds Max 8 SP 3, and I was wondering....is there a way to use procedural shaders to make a dirt map? I'm using Mental ray as my renderer, if that makes a difference.

firewolf

hrm...

so nobody knows how to do dirt maps using procedurals?

Sphynx

From a general perspective, a procedural used as a dirt map is going to be greatly dependant upon how much control you have over start and stop points.

I often was able to get a reasonable 'mud' map in LW by using a combination of brown/grey noise starting at the base of an object with a reasonably high falloff value to it disappeared very quickly after leaving the bottom of the object.

Otherwise, I think that you'll be looking at a light noise / cloud pattern with a subtle colour or opacity so that it breaks up the solid colours of the mesh. More than that on actually doing it in Max, you're going to need a maxer.

JustinDixon

nah, you nailed it pretty well. None the less, you'll need to make a UVW map of your mesh, and make it into opocity with falloff around the areas where you want the dirt. you're better off just painting it on like normal tbh, it's faster and allows for alot more control.

firewolf

how do you mean, paint it?

the only method of texturing that I'm familiar with is use of procedurals, selecting the elements or polygons that I want that particular map/shader on, and applying it to said region.

[Deleted User]

painting is when you unwrap a mesh into a uv and actually paint over with PS or GIMP.

tobian

I think the confusion here is that in Max a 'dirt map' is a way of saying 'ambient occlusion' in Max parlance. I am not aware if there is a way of doing it using textures, in Max, but the likelly answer is no, because it's a shader, deriving it's information from ray-casting and ray-tracing, not a mathematical fractal. On the flip side you might be able to use a dirt map with a procedural, to break it up a little, but I have no idea how, as I don't use max

From what I have read though, Mental ray should also do ambient occlusion 'dirt maps', how, I have no idea

aszazeroth

AOCC is only a matter of applying that particular MR-shader to the object, hit render and wait for a while. Control the sampling to play with spots.

General_Zod

Take some hi res pictures of some dirt. problem solved

firewolf

i was thinking, not a dirt texture, but a map where I can show bits of wear and tear on a model.

My modeling skills are ok, but they're not great, ya know?

[Deleted User]

...and by map you mean procedurals or an actual bitmap image?

firewolf

either one, though I would prefer procedurals

[Deleted User]

firstly, head over to maxplugins.de there's a dirtmap shader plugin (I never got it to work, tho).
on the other hand, for starters you could use a noise map that you mix unto the original texture map via a mask or something, gotta play around a bit until you get the desried result, tho.

hope that helps you

Larsen

I think you need to look up the basic mapping tuts in the manual or find some on the net. The dif MAX books out there are allso very good... You really need to familiarize yourself with max's map editor... sure you can get very far with procedurals, but you'll never be able to optain the kind of control over your textures that you'll have with real bitmaps!

When you got the basic mapping down...
1. Either use a bitmap, that you've made in PS or any other 2d app and slap it in the diffuse color slot.

2. Or create a black and white mask and use a mix or blend shader in the diffuse slot, in the mix or blend shader you can combine two textures either by mixing them or using the before mentioned mask!

D.M.J.

As far as I've found, there really is no substitute for doing it by hand with a soft brush in your image-editing app. My current favourite method is to find an edge in the mesh, then use PS's selection tools to select all the area on one side of that edge. Use a soft brush with low opacity and a nice grainy, streaky texture and brush carefully away from the edge keeping it random and believable. Then invert your selection and do the same thing to the edge from the other side. I find that that way helps to break up the edges and show dirt accumulating on the corners.

Beyond that, for procedurals and how to apply them, I'm afraid I will be no good for you

Jedilaw

There is a freely available ambient occlusion shader for Mentalray. I found it on 3d-Palace, along with a lovely short tut on using it. Do some searches under car paint materials, and AO dirt maps should come up in some of the tuts.

firewolf

thanks Jedilaw...finally some actual help, other than just some vague info

[Deleted User]

Here's how I would do a "procedural" dirt map with Mental Ray in Max.

I would start with a blend material.

In blend material I would assign Material 1 my base texture and Material 2 my dirt texture.

For a mask I would assign the ambient occlusion shader that comes with Max.

This would be ok looking. You should get the base material in open areas with the dirt showing up in nooks and crannies. For best results though, nothing beats doing it by hand.

Hope this helps.

firewolf

i'll have to try that once I get some sleep and then take my wife out to dinner...(she's been dealing with a lot since the baby was born)

Jedilaw

Heh. You act like babies are work or something. Try toddlers!

Just kidding. I have four, and I've been through the lack of sleep bit. I used to get in trouble in law school for falling asleep in class. The "I have a new baby at home" explanation worked with some of the profs, but not all...

@ndege: I hadn't considered doing a blend with the dirt map as the mask. That's not a bad idea at all.