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DarkBASIC Professional Discussion / Rendering speed - Use an alpha channel or a separate texture?

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pdq
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Posted: 11th Apr 2010 20:25
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I am writing a shader that will have an emissive property. Would it be faster to use a built-in alpha channel to an existing texture say from a colormap or specularmap or use a separate texture for the emissive map? Which method would render faster.

If using an alpha channel would be faster, would it be a rule of thumb to try to get as much information from alpha channels before adding more textures?

Thanks.
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BMacZero
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Posted: 11th Apr 2010 22:47
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I know traditionally that sort of thing is done in seperate images but who knows. Try 'em.

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Dr Tank
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Posted: 12th Apr 2010 01:38
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I'd say use a new texture. Just using alpha means you're limited to greyscale. Perhaps you're thinking that you would want a surface to emit the same hue as it scatters due to diffuse. But it's quite possible you may want them to be different.

For instance, you might have a surface that has neon lights on it.

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pdq
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Posted: 12th Apr 2010 05:25
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Yes, I am using a greyscale alpha to simulate the effect you mentioned - emitting the same hue as it scatters. So the next question then is if greyscale is fine, will using a new texture give me better performance or would it be the same? I can always experiment to find the answer. I am just wondering if the answer has already been found.
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