|Mixing textures in Photoshop and Softimage|XSI|
You probably have a small library of textures on your computer, what you might yet not know is that these textures can be combined in an almost infinite number of ways. I will show you two different methods of mixing textures. In this tutorial I will use two textures that I don't own the copyright to. The first texture (concrete) was downloaded from www.animax.it. Animax has a great library of textures and they can be downloaded for free. The second one (dirt/grime) was taken from the Surface Toolkit made by dvGarage. I really recommend that everyone working with texturing should buy this toolkit. It's a great resource when it comes to surfacing.
Mixing with different blending modes
What I did here was to load the two textures in Photoshop, copy the "dirt" texture on top of the other texture and lower it's opacity to 40%. As you can see the result has more white and the two textures doesn't blend together in a natural way. You can also see that it loses some of the detail. The problem gets even worse if you add more layers.
The solution to this problem is very simple. All you have to do is change the blending mode of the dirt texture. In Photoshop you can do this with the little dropdown menu in the layer window. In this example I will use the blending mode "multiply", but when you do this on your own it's a very good idea to experiment with different blending modes. The result will look something like this:
As you can see the result doesn't have that unnatural whiteness to it and the two textures blend together in a much more natural way. Using this method you can combine your textures into new ones without loss of detail.
Different blending modes aren't just good for surface textures. Another great way of using them is for lighting effects. Let's say you have a lensflare on a black background that you want to add on top of your image. Even if you are using alphamasks a black or gray border will show up around the flare. In Fig 3 I'm using "normal" blending mode and in Fig 4 I'm using "screen" blending mode.
As you can see the "screen" blending mode leaves the background as it is on all areas where the "screened" layer is black and where the "screened" layer is white the final result will also be white. This is exactly what we want since the only thing we want to show up is the white flare.
Mixing with alpha
Building textures with layers
1. Select the object you wish to texture and click Render->Modify - Shader.
2. In the window that
pops up click with your right mouse button on the little icon next to the
sliders for the objects color and select Blend
3. Press the "New" button and select the texture you wish to blend with the underlying texture/material.
4. Close the window and open up the rendertree. Double click the "diffuse_blend" node to open up it's property window.
5. In the window that pops up you'll see some parameters that controls the layer. The little icons on the right side means that you can map this parameter to a texture. Earlier I mentioned mixing by alpha masks and to do this in Softimage|XSI all you need to do is to map the image you want to use as transparency to the "Weight". Of course you can also use a simple color to control the transparency.
To demonstrate this I created a simple sphere, added the previously used concrete texture as base layer and added the dirt/grime texture to the first layer and set the mode to "Hue Offset (Overlay)".
As I see it using different blending modes is one of the most important things when creating graphics. If you aren't already working this way I really think you should take some time and learn it as there is a lot more to it than what I have written in this tutorial. Once you learned to work like this I think it's something you will use in almost all your graphic work. I really hope you learned something from this tutorial and if you have any questions please contact me at firstname.lastname@example.org Comments on this tutorial are also welcome.