View Full Version : Alpha Test Textures

06 June 2006, 08:41 PM
i was just reading a workflow for game asset creation with xsi. it talks about Alpha Tested Textures vs. Alpha Blended Materials.

it didn't go into the specifics of the the alpha tested texture, so i'm trying to find out more about it. like how it's created, how it's different from a blended, etc?

does anyone know here know? i'm actually not even sure if it's a specific function of xsi or a more general concept.


06 June 2006, 09:35 PM
An alpha tested texture in a game will check the alpha channel for transparency. If there is any kind of transparency, even 99% transparent, it will not draw. Alpha blended will make the texture more or less transparent according the the alpha channel.

Think of it like this, alpha tested is a boolean switch. It's either 100% transparent or not. A texture with 99% transparency that is alpha tested will not draw, whereas an alpha blended texture with 99% transparency will make it 99% transparent by blending the alpha channel with the RGB of the diffuse.

I'd reccommend picking up the book "3D Game Textures" for an excellent explanation with graphic examples.

06 June 2006, 09:51 PM
sweet! thanks for the book recommendation, i've already ordered it.

until it arrives, i was curious about the difference in how the texture is created, or how it is hooked up inside xsi, or both?

thanks again!

06 June 2006, 10:34 PM
Depends on the engine. In Source it's simply an entry in your VMT and pointing it to the alpha channel you want to use, in UE it's deciding which DXT format to export, neither of which is done in XSI. You can do a realtime preview in XSI with the appropriate shaders but this is work I do in Photoshop.

I'm not really familiar with any other engines so I can't comment on the pipeline for them.

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06 June 2006, 10:34 PM
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