D869 - A two-channel 8_8 target is drawn through an Rgba8 attachment

Status: decided Date: 2026-10-14

A colour target whose CB_COLOR0_INFO names COLOR_8_8, NUMBER_UNORM and SWAP_STD holds two bytes a texel, red then green (ac_formats.c ac_translate_colorswap, XY__). It lies by the two-byte layout, as the other two-byte targets do (D852, D868), a host carrying each texel's two bytes in a word's low half. A drawer draws it through R8G8B8A8_UNORM: the two bytes enter with blue zero and alpha one - what a format without them reads as - and leave as the two bytes alone. Draws write red and green only, so blending that reads destination alpha reads one.

Why: COLOR_8_8 is 3 (gfx103.json, enum ColorFormat). Grand Theft Auto V's second submission draws into such a target once its half-float target is drawn (D868). The word-a-texel handling of two-byte targets and the widening at the attachment's edges are D868's.

Rejected:

• An R8G8_UNORM attachment: its texels are two bytes, against the four every buffer sized by a texel's bytes carries for a two-byte target.