Quote:Original post by AAAP In photoshop.. you can't have 8bit alpha in targa. at least not in any that I've ever used, up to and including CS2.
What are you talking about ? Photoshop has had support for 8bit alpha channels in TGA for years. It's a very commonly used feature, actually:
Quote:Original post by AAAP or rather, the attrib byte is 8 bits... but still has on/off functionality.
No, it's not. Try it.
Quote:Original post by AAAP any targa format with greater than on/off functionality for alpha is an extension of targa, not the base format
The tga format hasn't been extended since 1989. And this is the version supported by all current graphics applications. And even the 1984 version supported 8bit alpha channels - why do you think they added a field that specifies the number of alpha channel bits ? The TGA alpha channel (encoded in the attribute channel) is not boolean, and has never been boolean. I don't know where you got that info from. Read the specs.
Sorry for this being offtopic, but I guess the OPs question has been answered anyway :)
Quote:Original post by Demus79 - D3D native format, fast load, supports compressed and uncompressed textures - perhaps harder to use with OpenGL, but I've seen examples about loading them on OGL - Old GPU's might not support them (pre-GF3)
a couple of things, theyre not native to d3d but are an api independant fileformat thus can be equalibly usable with opengl. (i in fact use them with gl with all manner of texture types eg cubemaps + 2d dxt3/5 (and uncompressed) + 3d textures with/without mipmaps ) all cards support the dds fileformat, though different subformats maybe limited eg gf2 doesnt support 3dtextures in hardware
In photoshop, for targa, in order to use the attrib bit, you need to make a 4th channel (alpha), which is basically a mask, read on/off. it will save the mask as the attrib bit, and thats your alpha. Though the pixel is 32 bits, the standard of the specification is to use an on/off functionality for the attrib bits, no matter how large they are. You can save a 32bit targa with an 8 bit alpha channel, but it's not the same as PNGs alpha capabilities.
PNG's alpha isn't just a mask, it's got the power to use multiple shades of "clear" as it were:P
if you rigged a image application to save a targa with the full 8 bits of alpha data, and rigged a viewer to display it, you COULD achieve that effect, but that's not directly in the specification, nor can you do that in photoshop.
When you want something to have 8 bits of color, and on/off alpha, what are you going to do. Specify that it use 25 bit pixels? imho the 8bit alpha in 32bit targas is for simplicity/compatibility. in fact, to defend my name, I defy someone to show me a targa that uses 8bits of alpha (so there is a clear display of several shades of alpha, if that makes sense ;p)
Yeah, if someone shows me that, I'll take back everything I've said about that, not that its relevent to this thread now anywy :)
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Quote:Original post by AAAP well ok, fair enough. I guess I haven't mentioned in this forum that I'm very much relentlessly opposed to using SDL in any project :o
Yeah, me too. Not sure why - maybe 'cos opengl and directx are used throughout the industry (game and film etc) and SDL is not. I mean, have you ever applied for a job that required SDL or halfway through the interview the guy says "are you proficient with the use of SDL"? So why waste time with SDL?
Negative.
SDL is for the use of 2d graphics. There are several commercial games that use SDL. Anyways, use of SDL is little because nowadays mostly all commercial games are 3d.
However, SDL has many more uses. It's usable for input, sound, window - managing, and everything else.
I'm currently (And I'm sure many others are too.) using SDL for everything except the drawing. All textures and other things are loaded/done in SDL.
P.S. Waste time with SDL? Don't tell me you just said that...
Quote:Original post by AAAP in fact, to defend my name, I defy someone to show me a targa that uses 8bits of alpha (so there is a clear display of several shades of alpha, if that makes sense ;p)
If you've played quake 3 then you've seen one. That's the only game I know that shipped with plain TGA files.
Quote:Original post by AAAP In photoshop, for targa, in order to use the attrib bit, you need to make a 4th channel (alpha), which is basically a mask, read on/off.
No, it's not. An alpha channel in photoshop can hold any greyscale value.
Quote:Original post by AAAP it will save the mask as the attrib bit, and thats your alpha. Though the pixel is 32 bits, the standard of the specification is to use an on/off functionality for the attrib bits, no matter how large they are.
No, it doesn't. Read the specification, and learn.
Quote:Original post by AAAP You can save a 32bit targa with an 8 bit alpha channel, but it's not the same as PNGs alpha capabilities.
It's an 8bit alpha channel, which can take values from 0 to 255. Nothing more, and nothing less.
Quote:Original post by AAAP if you rigged a image application to save a targa with the full 8 bits of alpha data, and rigged a viewer to display it, you COULD achieve that effect, but that's not directly in the specification, nor can you do that in photoshop.
There is nothing to "rig". This is standard TGA behaviour, and has always been. It is fully supported by all major applications that support TGA.
Quote:Original post by AAAP imho the 8bit alpha in 32bit targas is for simplicity/compatibility. in fact, to defend my name, I defy someone to show me a targa that uses 8bits of alpha (so there is a clear display of several shades of alpha, if that makes sense ;p)
Click. Unzip, open in photoshop, and watch the alpha channel.
Yann L is correct I use an 8bit alpha channel in my TGA files for storing height. Photoshop allows you to set the alpha channel value to anything 0-255.
I would use DDS format, it runs fast and ATI has a nice program that lets u manipulate the DDS files. You can prebuild mipmaps and even store entire cubemaps in one file.
Quote:Original post by AAAP hey if that's all true then i'll take your word for it, but im too busy atm to look at that.
Let me chime in here. Photoshop CAN indeed save a TGA file with alpha transparancy. You are correct that you need to mask it, but that mask can be a greyscale value which indicates partial transparancy. Why do I know? Counter Strike: Source uses a format which is typically converted from a .TGA file and you can most definitly get full alpha transparency in your cs sprays.
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