Tire Texturing - Page 1
The key component to making the object become a tire is going to be in the texturing. In no way am I professing to hold a great amount of texturing knowledge, but I can offer my method and hope it spurs you to advance it to your own needs.
The base texture that will be applied to the whole tire object is a simple dark grayish black color with some wide dull specularity. It strikes me as the kind of properties rubber would have...
Above you can see a dark gray in the color channel, very very close to black. And a wide dull highlight in the specular channel. These values are approximate only. Feel free to adjust to taste.
So that gives a fairly average depiction of tire rubber... Certainly it could be improved upon, but I'll leave that up to you. The main tire rubber material is perfectly suited to be enhanced to your liking, as it is not vital to the outcome of the other techniques.
The main tricks I'll be teaching are independent of this material, and can be used with a far more realistic rubber than this!
The tire wall will be a nice classic whitewall. To do this, I use a separate alpha texture (basically a decal material) that applies the whitewall right to the side of the tire using flat projection mapping and a restriction to the TireWall selection set. To set up the tire wall material, I used the following settings.
In the Color channel, the 'white' of the whitewall is actually a very basic neutral gray. Again, colors can be adjusted to suit your tastes. By the time the dull specular on this tire wall material lightens the appearance of the color, I find the material looks plenty 'white' enough for a tire!
Also mixed in is a small amount of default turbulence shader, just to provide a little bit of irregularity to the color. Maybe it's dirt or grime...
In the Diffusion channel, there is a default turbulence procedural affecting the specularity. The thinking behind this is that if the turbulence in the color channel represents some grime or dirt smudges, these smudges certainly won't have the same specular properties as the cleaner rubber.
You want to make sure that if you have this kind of relationship between channels, care is taken to make sure the maps or procedurals match!!!
Skipping ahead to the Specularity channel, I use a wide dull highlight for the whitewall. This is relative to the tire rubber of course, but is assuming the whitewall would have a larger wider highlight than typical dark rubber, just due to its lighter color.
Again, colors and materials are subjective here... if you can get it closer to your tastes, disregard the settings I use, and focus strictly on the techniques!
In the Alpha channel, I've placed a map that I made that will limit the effect of the material to a circular area. Only the area that is colored white in the alpha map will show texture when applied to the side of the tire.
I used a solid white circle rather than a ring so that if necessary, the texture size can be increased from the tire center without worrying about an inner radius for the texture not corresponding with the inner radius of the tire.
Take a look at the alpha map here.
Finally, in the bump channel, I've used a map based on the alpha map circle, but with the central portion of the circle effectively 'hollowed out', leaving just a thin ring that will run the circumference of the whitewall circle.
This bump just provides a nice transition between the two rubbers of the tire... maybe simulating a 'seam'. The bump value may seem a little high, but due this is due to the low contrast between the bright green background of the map and the white.
Take a look at the bump map here.
Now the material is applied to the tire object with settings as shown to the right (click to enlarge). Flat projection is used to basically project the circle right at the tire wall. It should be relatively centered, so won't need a lot of (if any) adjusting. I did have to rotate the heading setting by 90 degrees to get the material projecting from the proper direction. Note tiling should be turned OFF in this case, since this is like a decal we are applying.
The default size seemed to be about adequate too, and didn't require any numeric enlarging, but rather fit right how I wanted it to.
Luckily the real time texture map preview in Cinema XL allows us to manipulate texture placement and scaling, etc., without the hit and miss frustration of constant guessing and test rendering.
A look at the editor shows us that the whitewall is centered... and a render indicates it's looking okay! Let's continue...