dxt1 compression alternatives?
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The nvidia dxt compressor looks like junk if you give it a texture which is not really bright, unfortunately I need to give it textures and they come out horribly colour banded. Giving it the same texture which has been pre brightened gives a very nice result. Does anyone know of any dxt compressor alternatives, or am I missing a setting in the dxt1 compression settings?
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According to a PowerVR guy (the originators of the DXT format) "the RGB accuracy of all the DXTn variants is identical. Unfortunately, one series of graphics chips unpacked DXT1 into a 16 bit representation instead of the 24/32 bit it actually required." IIRC the only difference between 1/3/5 is how they handle alpha, DXT1 being the smallest because it has so little alpha to store.
Different compression libraries may use different methods to figure out what colors to store vs. toss out. You might try ATI's Compressionator. You can set it to show a difference image between compressed and uncompressed, so you can see the effects of various settings.
I thought this thread from DirectXdev mailing list was insightful.
http://discussms.hosting.lsoft.com/SCRIP...;D=1&P=2460
... basically there's nothing you can do about it.
Although you could also try adding some dithering before compressing, see if that helps.
According to a PowerVR guy (the originators of the DXT format)
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I hate to nitpick, but s3 did it first. Also, PowerVR's later Kyro cards could only do DXT1.
Hey any idea why PowerVR's tile-based sort never made it big? Their alpha sorting rocked so hard.
dxt1 = colour map no alpha
dxt3 = colour map black and white alpha
dxt5 = colour map gradient alpha
all compress the same quality but adding the different alphas increase the size of the file. Surprisingly next gen consoles do not seem to support palletized textures like the ps2 did so you are left with banded shite when baking lighting.