[***Texturing 101***]

Just to clarify something here...

 

The alpha channel of the color map .dds (ie the diffuse texture) you make indicates transparency with black being opaque and white being transparent (greys in between being different levels of transparency).

 

The alpha channel of the normal map is the actual specular map (since Oblivion's Gamebryo engine doesn't separate them you are restricted to grayscale of alpha channel) with black being the most matte non-shiny and white being the most shiny/reflective, again with greys being different levels in between.

 

If you save your .dds as dxt1 "no alpha" you will not save any of this alpha information. This is useful if you have only some color maps you don't have any transparency for or normals you don't care and just want the engine to fill in how shiny different parts are. If you save your .dds as dxt1 "1 bit alpha" it saves as very simple yes/no (black for yes, white for no) mask.

 

DXT1's are very low in size compared to DXT3 or DXT5!!!

 

If you save your .dds as dxt3 it saves it as "explicit alpha" and acts like the 1 bit alpha except it is 4 bit. It makes a mask just like the 1 bit dxt1 but has some blending at the edges available.

 

If you save your .dds as dxt5 it saves it as "interpolated alpha" and allows for a lot more greyscaling values.

 

 

A good example of the usage of this would be clouds and patterns.

 

If you use DXT3 for cloud transparency in the color map, you'll see banding, because of the 4 bit resolution, you'll want to use DXT5.

 

If you use DXT5 for patterns, the shape is not preserved inside a 4x4 pixel block like it would be with DXT3.

 

 

Most normal maps I've seen use DXT3 or DXT5 (although a few people just don't care and toss it in DXT1 with no alpha or black value as the alpha channel since they don't want any shinyeys).

 

I personally like to use DXT5 for things like paintings and stuff and DXT3 for things that just need masked. I find the masking with the 1 bit alpha in DXT1 kind of poor.