Halcyon

A cinematic, realistic shader for Minecraft Java 1.21.x, built for Iris + Sodium. It focuses on atmosphere: warm sunrises and sunsets, big soft clouds, reflective water, and a moody purple End.

Features

Sky

• Atmospheric scattering with warm sunrises, golden hour, pink twilight and a deep navy night
• Perfectly circular sun and moon, with real moon phases
• Stars that each twinkle at their own pace

Clouds

• Real 3D raymarched clouds with sun-lit edges and dark undersides
• Separate looks for clear weather, overcast and thunderstorms
• Cloud colour follows the real sun direction (orange and pink at sunrise and sunset)

Water

• Animated waves with subtle surface displacement
• Fresnel reflections: screen-space reflections, with sky, clouds and sun as the fallback
• Depth-based blue-green absorption, underwater caustics and shoreline foam

Weather

• Softened rain, wet surfaces that reflect the sky, and lightning flashes
• Rainbows after rain

Lighting

• Soft, coloured shadows (stained glass and water tint them)
• Ambient occlusion, contact shadows, god rays, bloom and filmic tonemapping

Dimensions

• The End: deep violet atmosphere with glowing light pillars, layered purple fog that hides distant islands, pale rim light on terrain, and violet-tinted blacks
• The Nether: dense haze tinted by the current biome

Settings

Four presets (Low / Medium / High / Ultra), plus individual options for:

• shadow resolution, distance and softness
• cloud quality, coverage and speed
• water detail, wave height, clarity, caustics and reflection quality
• ambient occlusion, god rays and bloom
• fog density (Overworld, Nether and End)
• star brightness and sun and moon glow
• rainbows, exposure, saturation, contrast and vignette

Requirements

• Minecraft Java Edition 1.21.x
• Sodium and Iris
• Not compatible with OptiFine or Bedrock Edition

Installation

1. Install Sodium and Iris.
2. Put the downloaded .zip into .minecraft/shaderpacks (do not unzip it).
3. In-game, open Options → Video Settings → Shader Packs and select Halcyon.
4. Pick a preset in the shader settings.

Performance

Heavier than a basic shader. The most expensive effects are the clouds, shadow softness and reflections. If it runs slowly, lower Cloud Quality first, then Shadow Softness Samples, then Water Reflections, or start from the Low or Medium preset.

Known limitations

• The rainbow is an approximation, because Minecraft does not report when rain has just stopped. It shows while the ground is still wet, rain is nearly over, and the sun is low.
• Clouds are drawn in the sky pass, so they cannot be shadowed by terrain.
• Not included: PBR and normal maps, Distant Horizons support, temporal anti-aliasing and Nether embers.

Feedback

Found a bug or want a feature? Open an issue or leave a comment with:

• your Minecraft, Iris and Sodium versions
• your GPU
• a screenshot or the Iris log

Credits

Created by VirtualAdi. Written from scratch for Iris.