Alpha Channel vs. Opacity Mask
Hello fellow artists! I was wondering what is the industry standard in regards to using either the alpha channel for transparency when creating a texture, or creating an opacity mask? In school we learn to utilize the alpha channel of a texture, but I was watching the Sci Fi Floor texturing video from 3D Motive and that artist uses an opacity mask with the RGB channels to set up his initial emissive, and transparencies.
I've also heard that the alpha channel creates another texture draw call on the game engine in order to render it, so its more resource intense. Any info to clear up the confusion would be great. Thanks guys.
I've also heard that the alpha channel creates another texture draw call on the game engine in order to render it, so its more resource intense. Any info to clear up the confusion would be great. Thanks guys.
Replies
So 2 DXT1s is the same size as a DXT5 and you have 2 extra channels you can do something with. Since he has an opacity and emmissive channel it is worth it to store in an extra DXT1.
@Computron, I'll keep that in mind. I wasn't really worried, its just I've seen two different methods to produce similar results and I just felt like asking which one may be the preferred method.
Remember in a Porftfolio, you will be showing your maps, guys that hire you couldn't care less about where you packed what, since it's varies between developments and pipelines.
For example, many people keep their Gloss map inside Specular Map's Alpha channel, since the two complement each other (having different size Specular and Gloss isn't advisable due to Mip-Mapping around the borders which could lead to 'cuts' where the two materials don't correspond).
But at the same time, many people use the full RGBA set of channel, each channel = own mask, in the case of Emissive.
Unless you're really trying to make a nice looking game while still pulling the double and even triple digits in the frames, then alot can be forgiven.