ColorTex

uniform sampler2D colortexN;

layout (<format>) uniform image2D colorimgN;

There are 16 color attachements available through the colortex0 through colortex15 samplers. These samplers can be read from any program, and can be written to from the fragment stage of any begin, prepare, gbuffers, deferred, or composite program.

Note: The final.fsh program appears to write to colortex0, however it actually writes to a display buffer with the resolution of the Minecraft window and RGBA format (usually equates to RGBA8) regardless of the size or format of colortex0. If colortex0 is set to non-clearing, any output written by final.fsh will not impact colortex0.

Writing to ColorTex buffers

Any begin, prepare, gbuffers, deferred, or composite program can write to a colortex buffer, the buffers to write to can be selected with the RENDERTARGETS or DRAWBUFFERS directive.

Additionally, you can read and write to the first 6 colortex buffer in Optifine or any colortex buffer in Iris using colorimgN where N is replaced with the colortex index. This is the only way to write to colortex buffers from compute shaders, but also works in any program. For more information on image load/store, see the Khronos Wiki.

Buffer size

These buffers default to the display resolution, although this can be configured with the size.buffer define in shaders.properties. However, changing the buffer size will prevent any gbuffer program from writing to the texture.

Buffer format/precision

All buffers default to RGBA format (which is RGBA8 on most systems), but this can be configured as described in the Texture Formats section.

Buffer clear

By default all buffers clear their values after each frame to solid black (all 0s including alpha), except colortex0 which clears to the fogColor with 1.0 alpha, and colortex1 which clears to solid white (all 1s including alpha). This clearing behavior can be configured with the colortexNClear directive, and the clear color can be configured with the colortexNClearColor directive.

Ping-Pong buffers

Each colortex sampler actually contains two buffers, which allows you to read and write to the same buffer in a composite/deferred pass. The buffer flipping behavior can be controlled with the flip.<program>.<buffer> directive.

Legacy Aliases

The first 8 colortex buffers have legacy aliases, although their names are often confusing and their use is not recommended. Except as noted below, either name can be used interchangably. The names are as follows:

colortex name	legacy name
colortex0	gcolor
colortex1	gdepth
colortex2	gnormal
colortex3	composite
colortex4	gaux1
colortex5	gaux2
colortex6	gaux3
colortex7	gaux4

Note: if gdepth is defined anywhere in the shader and the texture format for colortex1/gdepth is RGBA (or not specifically set by the shader), Iris will upgrade the format to RGBA32F. This represents legacy behavior, where gdepth was used to store depth values.