New feature: Pixel coverage
Added 2020-12-30 12:21:13 +0000 UTCPixel coverage is the amount of the pixel which is covered by a primitive. Pixels inside of a primitive have full coverage, pixels outside of the primitive have zero coverage, pixels on the edges of the primitive have partial coverage. Pixel coverage is used for anti-aliasing. N64 games also may use coverage for special purposes, such as wire-frame mode aka pen-and-ink mode. Pixel coverage must be computed on GPU level, but it is hard to get the necessary information from OpenGL. Thus, this feature was not emulated by any hardware graphics plugin until recently.
This December standard-two-simplex implemented coverage computation using barycentric coordinates of vertices. The idea is described here: https://github.com/gonetz/GLideN64/issues/2401
It is not the exact emulation of N64 pixel coverage. It is an attempt to get the same information using a completely different approach. Nevertheless, the result is very close to the original one. The screen shot above shows Turok 2 in PEN-AND-INC mode.
Comments
Several games have similar wire-frame mode. It also may help to remove delay in opening Zelda Ocarina of Time subscreen menu. Coverage information is also important for correct emulation of some blending modes. In short: this feature is unimportant for most of games, but for some of them it can be very useful.
2020-12-30 12:44:04 +0000 UTCAn interesting read! Sorry if this is a stupid question, but does this improve any other game?
Robert Dyson
2020-12-30 12:29:26 +0000 UTC
