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DaveTCode / GBADotnet

A C#/net core GBA emulator
MIT License
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Implement PPU blending #3

Closed DaveTCode closed 2 years ago

DaveTCode commented 2 years ago

BLDCNT/BLDALPHA are writeable but I do nothing with the values. BLDY isn't even writeable yet (just ignores writes). There's a TONC rom to test it and FFVI logo screens make good use of blending backgrounds as far as I can tell

DaveTCode commented 2 years ago

Great explanation of this from Fleroviux

Basically the compositor identifies the top two enabled, opaque (at the respective pixel) layers that aren't masked by a window first Then it applies blending/brighten/darken based on the SFX settings and layer select bits (and also the OAM alpha blend bit) For alpha blending you need to have both a source layer and destination layer for it to be applied meaning that you need to have two opaque layers to begin with and they must be enabled respectively as a blend source / destination Brighten/darken of course also check the respective SFX enable bit for the top layer