When creating patterns in The Sims 3, a big part of that process includes RGBA stencil masks. The following tutorial explains the purpose of RGBA stencil masks and what the individual RGBA channels do.
Installing DDS plug-ins
Working with The Sims 3 textures requires a DDS plug-in installed in your graphics program.
A pattern in The Sims 3 has four channels to hold mask information. These are Red, Green, Blue and Alpha (RGBA) where every channel can save a greyscale image. The following pattern is going to illustrate the concept of stencil masks, not the making of the pattern itself.
Breaking up the above pattern in its color layers gives us the following:
Now we sort these layers in channels and make them greyscale, so they work like alpha masks for the colors. White is fully opaque, black is invisible, and greys are transparent.
Create the RGBA Stencil Mask (Photoshop)
Open a new 256×256 pixel RGB/8 document.
Change to the Channels tab and add an Alpha, since there are four channels in this pattern. You don’t have to add the Alpha channel if you have only 3, 2 or 1 channel used for your pattern. Don’t delete any of the RGB channels.
Photoshop won’t like that.
Each of those masks is copied into the correct channel.
With Alpha visible, the image will look something like this.
It looks odd but this doesn’t matter as long the masks in channels are correct.
Go to Save as and choose the D3D/DDS (*.DDS) file format with Alpha channel enabled. Hit Save and the DDS plug-in dialog pops up. Choose the DDS internal format 18.104.22.168 ARGB 32 bpp | unsigned from the drop down list and click Save.
The file is now ready to import into the TSR Workshop 2.0 Pattern Tool. If you’re unsure how to use it, see the TSR Workshop Pattern Tool Manual.
Note: Almost all kind of meshes in the Sims 3 do have a Stencil Mask. This time they don’t hold colors, but they are the mask for patterns to compose the final mesh texture.