Firmament

Faster clouds in rain and tidier shader code, with exactly the same picture.

Changed

• Under the hood: repeated shader code now uses shared helpers, the reflection-snapshot pass decodes each pixel once, and unused declarations are gone.

Performance

• Clouds in rain: about 1.05× faster. Cloud samples that are already fully dense skip noise that cannot change them; higher Cloud Coverage settings benefit too.
• Nothing slower: every other pass costs the same as in 0.2.1. Four further optimization ideas were measured and left out because they were not faster.
• Timings are isolated GPU pass measurements against 0.2.1 on an RTX 4060 Laptop GPU at 2560 × 1440 with the High preset, not frame rates. The sky, fog and night-sky speed-ups of 0.2.1 are kept.

Compatibility

• The same 29 Minecraft Java versions as 0.2.1: 1.18.2; 1.19, 1.19.1, 1.19.2 and 1.19.4; 1.20–1.20.6; 1.21–1.21.11; 26.1, 26.1.1, 26.1.2, 26.2 and 26.3.
• Use the Iris and Sodium builds matching your Minecraft version; 26.2 and 26.3 target the OpenGL renderer. Recorded gameplay evidence remains 1.21.1 / NeoForge 21.1.228 / Iris 1.8.12 / Sodium 0.6.13 with 0.1.0-alpha.2.

Known issues

• After reloading chunks with F3+A, shadows of blocks outside your view appear once you look at them: Iris only builds chunks the camera sees.

Notes

• Same image: every automated comparison image is bit-identical to 0.2.1; rendering, presets and options are unchanged.
• Keep the ZIP intact, place it in shaderpacks, select Firmament in Iris, start with High and adjust the preset for your setup.