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Numsgil

Setting photoshop's alpha channel bit depth

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We're using DDSs at work. The artist I'm working with is reluctant to use DXT1 because when he exports a picture from photoshop, the alpha channel gets squashed to 1 bit making the edges of things really ragged. Is there a way to set the bit depth of the transparency channel so that when he's working in photoshop he'll see exactly the alpha he'll get when he saves it as a DDS?

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If you don't want things to look jagged you really just need to use DXT5.

Otherwise, he should simply be painting the alpha in white and black. Anything else would just be guesswork. Jack up the contrast then use the pencil tool from then on.

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We could do DXT5s, but the alpha really has no business being a gradation anyway. The fact that it is probably has more to do with his eraser tool being set to brush instead of pencil. And DXT1s save a little bit more space than the DXT5s (DXT5 is twice as large as the DXT1).

I could try and teach him to only use the pencil eraser tool, etc. but it would be kind of an old-dog-new-trick situation. It would be much easier if there was a way to simply force the alpha channel bit depth to 1 bit. Or even just isolate the alpha channel and force a tolerance on it, or something like that.

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Original post by Numsgil
We could do DXT5s, but the alpha really has no business being a gradation anyway. The fact that it is probably has more to do with his eraser tool being set to brush instead of pencil. And DXT1s save a little bit more space than the DXT5s (DXT5 is twice as large as the DXT1).

I could try and teach him to only use the pencil eraser tool, etc. but it would be kind of an old-dog-new-trick situation. It would be much easier if there was a way to simply force the alpha channel bit depth to 1 bit. Or even just isolate the alpha channel and force a tolerance on it, or something like that.

Have him make the alpha as he pleases, but then when he is done have him crank up the contrast to 100%. This will make all pixels absolute white or black. But again, this will still be guess work as it is hard to tell which pixels will go white and which will go black.
As such, i recommend turning off anti-aliasing for the brushes instead.

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Is there a way to view the alpha channel like I can view the red, green, and blue channels?

Yeah... unless you're doing alpha channeling different, the alpha channel should appear right under the rgb channels. Simply hide the rgb channels and select the alpha channel and you should be able to view it.

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I see RGB, Red, Green, Blue. No alpha. Is there some sort of mode I have to go in to?

Nope, you should see it, simply create a new channel under that tab and it should be an alpha channel.
How is the artist doing them?

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Original post by Jarrod1937
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Original post by Numsgil
I see RGB, Red, Green, Blue. No alpha. Is there some sort of mode I have to go in to?

Nope, you should see it, simply create a new channel under that tab and it should be an alpha channel.


Ah, yes. But while it's called an alpha channel, it's not really a channel to show transparency, is it? Near as I can tell it's just an extra data channel?

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How is the artist doing them?


I'm not sure, actually. He tends to get impatient when he tries explaining this stuff to me. We really have a whole different vocabulary for things.

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Original post by Numsgil
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Original post by Jarrod1937
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Original post by Numsgil
I see RGB, Red, Green, Blue. No alpha. Is there some sort of mode I have to go in to?

Nope, you should see it, simply create a new channel under that tab and it should be an alpha channel.


Ah, yes. But while it's called an alpha channel, it's not really a channel to show transparency, is it? Near as I can tell it's just an extra data channel?

Quote:

How is the artist doing them?


I'm not sure, actually. He tends to get impatient when he tries explaining this stuff to me. We really have a whole different vocabulary for things.

Yeah, the alpha channel is simply another extra 8 bit grayscale data channel. It can hold grayscale maps for a variety of things, including shaders.
However, it is most used for alpha testing (1 bit transparency) and alpha blending (8 bit transparency). Checkout the "Bit depth" section of my guide for more information.

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