Sims 3:DXT Compression Types

Textures

The vast majority of your CAS part will be defined with textures. The following is a list of all the possible textures, and what they edit on the CAS part.

Texture	Use	Compression	Alpha Needed
Base Texture	The base texture--sometimes called the multiplier---maps out what parts of the mesh are used (via the alpha layer) and it adds texture (wrinkles and folds) to the CAS part.	DXT5	Yes
Clothing Ambient	The clothing ambient indicates lighting intensity of the CAS part. This is rarely used, even by EA, so most are left pure white.	DXT1	No
Clothing Specular	The specular indicates the shininess or reflectivity of the CAS part.	DXT1	No
Mask	The mask uses the Red, Green, Blue and Alpha channels to define the different regions (patterns) that are recolorable using the Create-A-Sim tool.	DXT1	No*
Overlay	An overlay is similar to a stencil except it can be placed anywhere, whereas a stencil is confined to the perimeter of the base texture's alpha. Necklaces that are attached to a clothing item are usually overlays.	DXT1, DXT3, DXT5	Yes
Part Mask	The part mask maps out the minimum physical space the CAS part takes place in and is used by the game to map out how different outfit textures parts overlap. For example, it keeps knee-high boots textures from overlapping pants textures. In general, you won't have to change this unless you're doing some extreme retexturing such as turning pants into shorts.	DXT1	No*
Skin Ambient	The skin ambient is similar to the clothing ambient, except it indicates the lighting intensity on the skin itself. For the most part all default ambients are the same, so there's really no need to change it.	DXT1	No
Skin Specular	Skin speculars are like clothing speculars, except they indicate the reflectivity/shininess of the skin itself.	DXT1	No
Face Overlay	Face overlays are the equivalent of base textures for the face. These are used to make anything that deals with the face like: custom face masks, makeup, eyebrows, etc. When dealing with face overlays, instead of assigning pattern colors, you give each part a tint color. To change the color either double-click on the little colored squares at the bottom of the textures window, or right-click on the tint key and hit edit color.	DXT5	Yes
Bump Map	Bump maps are alpha-layered grayscale images that are used by the game to simulate raised bumps and grooves on the texture.	DXT5	Yes

* If you have four pattern regions you'll need to include the alpha channel.