airefresco Wrote:
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> And while i am here, what the difference between DTX1 and DTX5 tex
> files?
>
> paul..
In short: the alpha channel.
If you don't use the alpha channel then always use DXT1 because DXT5 will only double the filesize and nothing more.
If you do use alpha on the texture then DXT1 is able to store a 1 bit alpha, which means something like alpha enabled or disabled per pixel.
DXT3 has an explicit 4 bit alpha, which means that you can have 256 different shades of the alpha channel per pixel.
DXT5 is similair to DXT3, except that it has an interpolated alpha channel.
Interpolation is something like anti-aliasing. It's a type of curve fitting.
[edit]
In addition:
DXT3 might also be useful as it's the most 'true' representation of the image processed in your image editor (which works with pixels)
Some scenarios here:
You made a helmet and the only perpose for the alpha channel is transparency. There's no need for a gradient type of transparency because your visor is just plain glass. Then you'd pick DXT1. Alpha on or off per pixel.
your helmet uses a visor and the top is darker than the bottom. then you could use DXT3 or DXT5.
DXT3 uses the exact same image as you would save it to TGA. 256 levels of transparency per pixel.
So if you need a very detailed alpha channel then DXT3 is the best choice.
But this also has a downside: Textures easily become very 'grainy' because of the detail.
DirectX doesn't use pixels as we know it and Microsoft invented DXT5. This lets the alpha 'bleed' a bit.
when your original texture has a sequence of alpha pixels like 255,0,127,255 then DXT5 will (for the eye) make it something look like this 255,80,200,255.
Sounds like there's image-loss there and there is, but this avoids you from making 2048 pixel textures for simple small textures. So it's some sort of intelligent blur if you like
I'd rather have a bottle in front of me than a frontal lobotomyEdited 1 time(s). Last edit at 09/14/2006 02:46AM by ZaZ.