Rust/Dirt -- 3ds Max

T

TheSpook

Limp Gawd
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Feb 12, 2004
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Work and graduate school applications have calmed down recently, giving me some time to play around in 3ds Max. I'd like to add some rust or dirt to the geometry in both of the following scenes (the current materials are just placeholders :)).

bolts_03.png


tech_art_05.png


Here are my thoughts:
The rust/dirt should be heaviest on the top of the bolts/pipe, because the top bits will have been exposed to the most weather.

Maybe adding a planar UVW modifier above each bolt would work? I'd be able to project a texture straight down onto the bolt. I . . . actually have no idea what to do. Any suggestions? Don't have much experience in this department.

Edit: Darn PNG transparency.
 
I'm looking to have the rust available for future images rendered from different viewpoints, et cetera -- so Photoshop would be a temporary fix.

Those are some good tutorials -- I've looked at the first, at least, in the past. (Thanks for the links to the new stuff, too :)) You are probably right about the rust occurring everywhere at a fairly equal rate, but I'd like to add some dirt/something stylized that is heavier on the top of the bolts than the bottom. I'm not really sure where to get started with that, since the "top" of each bolt depends on how it is positioned, et cetera.
 
You have two choices, basically.

The first is to create actual UV maps for each bolt (google it, if you don't know what UV mapping is). Then you can paint the rust in Photoshop, and apply that in 3D space to your bolts.

Your other option is to do simple cubic projections of images of rust onto the bolts. Mix it up with a few layers of different rust and a few procedural noise textures and whatnot, and you can get really nice results.
 
Black Morty Rackham said:
You have two choices, basically.

The first is to create actual UV maps for each bolt (google it, if you don't know what UV mapping is). Then you can paint the rust in Photoshop, and apply that in 3D space to your bolts.

Your other option is to do simple cubic projections of images of rust onto the bolts. Mix it up with a few layers of different rust and a few procedural noise textures and whatnot, and you can get really nice results.
Click to expand...

Or he can do it procedurally. The dirt shader modi linked to is basically just a variant of ambient occlusion, which is readily available in mental ray. AO shaders are frequently used as dirt maps.
 
Auric said:
Or he can do it procedurally. The dirt shader modi linked to is basically just a variant of ambient occlusion, which is readily available in mental ray. AO shaders are frequently used as dirt maps.
Click to expand...
Rust that's done completely procedurally doesn't actually look good, though. It always looks better if you mix in a few simple cube-mapped image maps and stuff.
 
It does seem like I'm going to need to do a bit of personalization with these rust maps -- I've been messing around with doing things entirely procedurally, and it does not look all that convincing.

Photoshop time. Thanks to all for their comments; renders will be posted eventually!
 
I don't know how much you know about mental ray shaders in 3dsmax (probably more than me), but one thing that would really help is using an ambient occlusion that's biased upwards to mask in more eroded rust.
 
Black Morty Rackham said:
Rust that's done completely procedurally doesn't actually look good, though. It always looks better if you mix in a few simple cube-mapped image maps and stuff.
Click to expand...

That depends on how complex you're prepared to get with nested shaders, but using texture maps is certainly easier.
 
Some of my recent shaders have as many as 120 or so nodes in them. I guess if I did it in layers, it'd be about 100 layers per channel. Complexity is fun! :)
 
one problem I'm noticing is that if a bolt rusts it usually wears down so taking perfect models of bolts and putting "rust" effects on them looks out of place because it seems to perfect to already have rust. Just my opinion.
 
Destonomos said:
one problem I'm noticing is that if a bolt rusts it usually wears down so taking perfect models of bolts and putting "rust" effects on them looks out of place because it seems to perfect to already have rust. Just my opinion.
Click to expand...

That is a very good point. However, any aberrations on the bolts from rust will be really minute relative to the size of the actual bolts -- do you think people would actually notice such small changes to the geometry?

I will play around with that a little, though -- thanks for the insight.

As for the actual rust texturing -- I've been held up with work recently, but have been messing around using different Falloff maps for different portions of the texture, and have been having some success using the "World-Z" type of Falloff.

One day, pictures will be posted. I swear :p!
 
TheSpook said:
That is a very good point. However, any aberrations on the bolts from rust will be really minute relative to the size of the actual bolts -- do you think people would actually notice such small changes to the geometry?

I will play around with that a little, though -- thanks for the insight.

As for the actual rust texturing -- I've been held up with work recently, but have been messing around using different Falloff maps for different portions of the texture, and have been having some success using the "World-Z" type of Falloff.

One day, pictures will be posted. I swear :p!
Click to expand...

primarily more at the top of the bolt where there are a lot of perfect edges which would be wore down mainly.
 
Really for something that would need a natural, grimey look, its hard to beat what Zbrush/Mudbox can do for things of that nature. Its really probably easier too, than getting a procedural approach with a million nodes (not time efficient) that actually looks nice.
 
maverick212 said:
Really for something that would need a natural, grimey look, its hard to beat what Zbrush/Mudbox can do for things of that nature. Its really probably easier too, than getting a procedural approach with a million nodes (not time efficient) that actually looks nice.
Click to expand...
Easier on one bolt, yes, but unless you want all 150 of them to look exactly the same, you will need something projected in world coordinates, instead of UV. That's the advantage of doing it procedurally: Once you have ONE bolt looking nice, can have however many bolts you want, all unique.
 
Just do a couple, make sure both sides are radically different. Creative placement, then flipping them over, placing them certain ways.
 
On the other hand, if you're doing like three or four different variants, you might actually be able to build some pretty nice procedural rust...

Both methods have their advantages and disadvantages. I'd probably go for a mixture between both painting a few simple maps AND adding procedural, world-coordinates stuff on top.
 
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