Secessionist
Banned
Could the Dreamcast do it? Why/why not? Did any games use it or did they all use 16 bit RGB with dithering?
32 bit RGBA frame buffer with the Dreamcast
- Thread starter Secessionist
- Start date
Dungeonscaper
Newcomer
Would someone mind explaining exactly what dithering is in layman's terms. It seems like a very abstract idea to me.
Wikipedia. Don't worry about reading it. Just look at the example images near the bottom, and you'll see dithering in action. It basically gives the impression of more shades than the actual number of colours used. This in turn requires less RAM and bandwidth for drawing dithered graphics, although the quality isn't as good as if you spare the bits to get more colour/transparency resolution.
It's still used in games today. Wii maintains GC's 16 bit dithered colours, while even 32 buit platforms like PS3 and 360 have dithering when using the alpha-to-coverage technique to draw transparencies.
It's still used in games today. Wii maintains GC's 16 bit dithered colours, while even 32 buit platforms like PS3 and 360 have dithering when using the alpha-to-coverage technique to draw transparencies.
The way I remember it is tiles always used 32bit internally, and FrontBuffer was usually 16bit to save VRam (which was a precious resource shared with display-geometry and textures, so it was likely common to use 16bit FB).
Because downsample to 16bit only happens on resolving to FrontBuffer, color loss artifacts are minimal (alpha blended stuff doesn't get screwed up and so forth), but yes, there will still be dithering of course.
To be fair, 16bit looks virtually perfect on SDTVs doing it this way (it only gets ugly if you do entire rendering in 16bit, which was more common with GC/Wii and PSP games).
But moving to fixed pixel HDTVs, things tend to look ugly anytime you use dithering and pixel resolution that isn't display native.
Because downsample to 16bit only happens on resolving to FrontBuffer, color loss artifacts are minimal (alpha blended stuff doesn't get screwed up and so forth), but yes, there will still be dithering of course.
To be fair, 16bit looks virtually perfect on SDTVs doing it this way (it only gets ugly if you do entire rendering in 16bit, which was more common with GC/Wii and PSP games).
But moving to fixed pixel HDTVs, things tend to look ugly anytime you use dithering and pixel resolution that isn't display native.
Just to add to Faf's reply, according to my spec, DC's framebuffer had 7 framebuffer pixel formats:
- 0555
- 565
- 4444
- 1555 (mapping of alpha from internal 8888 is determined by a threshold register setting (I think))
- 888 (packed 24-bit RGB )
- 0888 (32-bit RGB)
- 8888 (32-bit ARGB)
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