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Autodesk Multimedia Forum · Autodesk Animator

WHERE DOES AS GET ALPHA?

6 messages in this thread

#181713From: Debbie BerneJul 24, 1995 2:30 AM

I can't figure out where Animator Studio gets it's alpha channel info from. I just imported a series of TGA images with embedded alpha channels. When I tried to use the alpha info to make a mask, it seems as though its just using the RGB info to make the channel. When I did a view alpha, the black areas (outlines surrounding colored areas) were all transparent (100% alpha), and the colored areas were partially transparent. The TGA embedded alpha, however, was completely black and white; the stuff that came out partially transparent in AS was completely black in the TGA alpha channel. What am I missing? Does AS not recognize an alpha channel tagged onto the end of a TGA file an just make it from the RGB info? Thanks in advance, Dave Renneker

#182359From: dave aguilarJul 26, 1995 8:08 PM

>> What am I missing? Does AS not recognize an alpha channel tagged onto the end of a TGA file an just make it from the RGB info? << i'll forward this to tech supp… i just tried this out and had same thing happen. -dave

#183331From: Brent BlackettAug 2, 1995 11:41 PM

It depend upon whether the file is pre-multiplied alpha or not. Right now we read alpha properly from 3D Studio, but not all other programs. This is something we're working on. -Brent Blackett

#183336From: dave aguilarAug 2, 1995 11:53 PM

>> It depend upon whether the file is pre-multiplied alpha or not. Right now we read alpha properly from 3D Studio, but not all other programs. This is something we're working on. << is this regarding alpha being associated or unassociated (matte versus pre-multiplied)? -dave

#183350From: Debbie BerneAug 3, 1995 1:26 AM

Hopefully it's an entire topic (pre-multiplied alpha?!?) I want have to learn to much about in the future. So does this mean that a 32-bit TGA file from Photoshop won't have it's alpha read properly yet, or is it something I'm doing wrong? Thanks for any info Dave Renneker

#183358From: dave aguilarAug 3, 1995 4:13 AM

>> Hopefully it's an entire topic (pre-multiplied alpha?!?) I want have to learn to much about in the future. So does this mean that a 32-bit TGA file from Photoshop won't have it's alpha read properly yet, or is it something I'm doing wrong? << there are programs which save the alpha in different ways… the terms folks use to describe these ways are premultiplied (or associated) and matte (or unassociated). AAS checks a flag, if it reports unknown, AAS assumes it is premultiplied. if the original alpha was matte, view alpha can act strangely. -dave