Alpha Piscium is a high-quality realistic shaderpack for Minecraft, built around cutting-edge rendering techniques to deliver physically accurate lighting, skies, shadows, and materials. Every visual system in Alpha Piscium is grounded in real-time research — from reservoir-based global illumination borrowed from AAA graphics pipelines, to atmospheric scattering models adapted directly from Unreal Engine — making it one of the most technically ambitious shaderpacks available for the game.Documentation Index
Fetch the complete documentation index at: https://mintlify.com/Luna5ama/alpha-piscium/llms.txt
Use this file to discover all available pages before exploring further.
Core Rendering Features
Alpha Piscium implements a broad suite of modern rendering techniques that work together to create a cohesive, realistic look.Real-Time Global Illumination
Global illumination is computed using ReSTIR SSGI — Reservoir-based SpatioTemporal Importance Resampling applied to Screen-Space Global Illumination. This algorithm, originally developed by NVIDIA, intelligently resamples lighting candidates across space and time to produce stable, high-quality indirect lighting at real-time performance. Denoising is handled by ReBLUR, a recurrent blur algorithm that refines the GI signal over multiple frames.Atmospheric Scattering & Light Shafts
The sky is rendered using the Unreal Engine Sky Atmosphere technique, a physically based model that accurately simulates Rayleigh scattering, Mie scattering, and ozone absorption across the full day-night cycle. Volumetric light shafts (god rays) are rendered using epipolar sampling, an efficient method that concentrates ray-marching samples along the direction of sunlight for crisp, high-quality aerial perspective.Volumetric Clouds
Clouds are modeled with the Nubis technique, originally developed by Guerrilla Games for Horizon Zero Dawn. Alpha Piscium supports two cloud layers — puffy low-altitude cumulus clouds and wispy high-altitude cirrus clouds — each with independent controls for altitude, density, coverage, and wind movement.Shadows
Shadow rendering uses RTWSM (Rectilinear Texture Warping Shadow Mapping), an adaptive technique that redistributes shadow map resolution based on where detail is most needed in the scene. Soft shadow edges are computed with PCSS (Percentage-Closer Soft Shadows), which produces realistic penumbra sizes that scale with the caster’s distance from the receiver and the angular size of the sun.PBR & LabPBR Material Support
Alpha Piscium supports Physically Based Rendering with full LabPBR material format compatibility, including normal mapping, specular reflections, and subsurface scattering on blocks. Both auto-detection and forced LabPBR modes are available. A built-in material mode is also provided for use without a dedicated PBR resource pack.Post-Processing & Visual Effects
The post-processing pipeline includes:- Temporal Anti-Aliasing (TAA) with sub-pixel jittering and configurable history filters for clean edges across frames
- Depth of Field (DoF) with physically based aperture simulation, configurable focal length and f-stop, and circular or hexagonal bokeh shapes
- Tone mapping using AgX with configurable dynamic range and color grading presets (Default, Golden, Punchy, and Custom)
- Water caustics — realistic light patterns cast onto surfaces beneath water
- Purkinje effect — the physiological shift toward monochrome, blue-shifted vision in low-light conditions, simulating how human eyes actually perceive darkness
- Bloom with configurable spread, intensity, and highlight compression
Requirements
Alpha Piscium requires Iris 1.7 or higher as the shader loader. Fabric/Quilt with Iris, or the standalone Iris installer, are both supported. Modern NVIDIA or AMD GPUs are recommended; Intel GPUs are not supported. See the Requirements page for full hardware and driver details.Community & Downloads
Modrinth
Download the latest release of Alpha Piscium from Modrinth.
Discord
Join the official Discord server for support, previews, and community discussion.
Get Started
Installation
Step-by-step guide to downloading and activating Alpha Piscium in Minecraft using Iris.
Requirements
GPU compatibility, driver version requirements, and supported mod loaders.
Configuration Profiles
Explore the six built-in quality presets from Low to Insane.
PBR Resource Packs
Pair Alpha Piscium with a LabPBR resource pack to unlock full physically based rendering.