I can't speak for his problems of course but for me alpha in png has the obvious problem of losing the alpha-ed out portions of the image when I load the png. I use png for my alpha transparency needs but I always have to work on and save from a non-png version (as you pointed out to do with jpg images) because loading the png image loses a lot of information.
Mustang, note that doing alpha transparency for png is fundamentally different than for tga images. With the latter you simply create a new channel called "alpha." While this technically works with png you end up with ugly white halos due to anti-aliasing and the fact that alpha-ed out portions of the image are turned white when the png is saved. Instead you need to set the image as a layer, eliminate all other layers (including the background layer,) add a mask to the image layer, and paste your alpha image onto the mask's channel.
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Skitchy, things are a little different with sprites (as mark indicated) but for most entities surfaces are allocated by entity first, and then further split up based on texture/material within and entity. So even if they all have the exact same texture/material, 10 separate entities are 10 separate surfaces.
Mustang, note that doing alpha transparency for png is fundamentally different than for tga images. With the latter you simply create a new channel called "alpha." While this technically works with png you end up with ugly white halos due to anti-aliasing and the fact that alpha-ed out portions of the image are turned white when the png is saved. Instead you need to set the image as a layer, eliminate all other layers (including the background layer,) add a mask to the image layer, and paste your alpha image onto the mask's channel.
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Skitchy, things are a little different with sprites (as mark indicated) but for most entities surfaces are allocated by entity first, and then further split up based on texture/material within and entity. So even if they all have the exact same texture/material, 10 separate entities are 10 separate surfaces.