21–30 of 97 posts
The issue with the Limbo logo was not that the source image was incorrect. The image was fine. The blending was incorrect because the PS3 XMB has a bug. Not using premultiplied alpha when you are doing texture filtering is a bug.
The correct solution is to pay close attention to all of the factors... and to be ESPECIALLY aware of pixel scaling. Provide your RGBA textures at the 1:1 pixel scale they will be rendered (or higher!) if at all possible.
Premultiplied alpha results in less color depth, though. If my alpha is 10%, then my possible RGB values become 0-25. Even if I multiply by 10, I still lose the maximum possible values 251-255, and only values 0, 10, 20, 30... 250, are possible. The correct solution is to pay close attention to all of the factors... and to be ESPECIALLY aware of pixel scaling. Provide your RGBA textures at the 1:1 pixel scale they wi…
> pay attention to what color you put inside the transparent pixels I don't understand this. When I make transparency I don't use any color? I use the Eraser tool or Ctrl-X, not a color with 0 opacity.
This is actually a very common problem with 3-D stuff and transparency in textures. This isn't an issue with the colors of the pixels themselves, it's an issue with texture filtering. nVidia has a pretty good explanation as it applies to games and 3d graphics: https://developer.nvidia.com/content/alpha-blending-pre-or-n... Say you have two adjacent pixels using floating point RGBA values of (0,0,0,0) and (1,1,1,1), a…
Also: "The original color can still be retrieved easily: dividing by alpha will reverse the transformation."
C'mon, you can't say that and then make an example with alpha=0. Do you want me to divide by zero? The ability to store values in completely transparent pixels is lost.
This is extremely useful to take advantage of (that you can store RGB values in 0-alpha pixels). I've written some pretty simple but powerful shaders for a game I'm working on by utilizing transparent pixels' "extra storage" which allowed for either neat visuals or greatly reduced the number of images required to achieve a certain affect. For instance, I wrote a shader for a characters hair that had source images col…
> Even with an alpha of 0, a pixel still has some RGB color value associated with it. Wish the article was more clear as to why this happens. Let me elucidate: this happens because, per the PNG standard[0], 0-alpha pixels have their color technically undefined . This means that image editors can use these values (e.g. XX XX XX 00) for whatever -- generally some way of optimizing, or, more often than not, just garbage…
While what you wrote is correct, it's not actually the problem being described in the posted link. The problem in the posted link is just as relevant if the alpha value was "01" for "you pretty much can't see it but it's meaningfully there", and has to do with image filtering artifacts as opposed to purely data representation.