GPTShader

A fantasy-soft Iris shader pack for Minecraft Java 1.20.1, built around warm filmic
lighting, a fully procedural sky and water, and deep in-game tuning — every major
effect can be reshaped from Iris’ Shader Pack Settings screen without editing a
single file.

Requirements

• Minecraft Java 1.20.1
• Iris (or an OptiFine-compatible loader)

Presets

Four starting points, switchable anytime from the settings screen — each one just
sets the sliders below to sensible defaults, so nothing is locked in:

• Clear Water — brighter, higher-clarity water and a lighter overall look
• Balanced ("Fantasy Cozy") — the default, tuned for a soft, storybook feel
• Cinematic — deeper shadows, richer color, stronger glow and reflections
• Fast — trims shadow resolution and the heavier effects for lower-end hardware

Every value a preset sets can still be adjusted individually afterward.

Features

Lighting & Shadows

• Soft PCF sun shadows with rotated Poisson filtering and a nonlinear shadow-map
  projection that concentrates detail near the player (2048–8192 resolution)
• Screen-space contact shadows at block edges, corners, and steps
• Directional face shading, block-form depth, and backlit foliage transmission
• Adjustable sun glare, colored lens flare, and moonlight with real lunar
  directional lighting
• Held-light system: torches, lanterns, glowstone, soul lights, redstone, and lava
  buckets cast their own correctly colored dynamic light from either hand

Sky & Atmosphere

• Fully procedural sky — gradient daylight, warm sunrise/sunset, twinkling stars,
  and a soft blue-white Milky Way band, all seamless around the full horizon
• A proper moon: correct 8-stage vanilla lunar phases with a real curved
  (sphere-shaded) terminator instead of a flat chord cut, and orientation that
  rolls across the sky the same way vanilla’s does
• A rare aurora event with a folded multi-band curtain — vertical rays, drifting
  bright knots, and a green-to-violet gradient — with an adjustable frequency
  slider (occasional sightings up to appearing every night)
• Occasional shooting stars
• Volumetric-styled clouds: coverage, density, altitude, thickness, speed, and
  shape evolution are all independently tunable, with sun-lit rim shading
• Distance fog, aerial perspective, and atmospheric haze

Water

• Fully procedural water surface — no vanilla water texture — combining broad
  swell with multiple non-repeating ripple scales
• Depth-based color and opacity: clear shallows fading into tinted, absorptive
  depths, with four selectable base color presets
• Sky, cloud, and sun reflection at every height, plus short-range screen-space
  reflection of nearby scenery
• Silver sun-glint trail and shoreline foam

Materials & Reflections

• Ores, torches, redstone (red), soul lights (blue), sea lanterns (cool blue-white),
  end rods, amethyst, froglights, magma, lava, crying obsidian, and glow lichen
  each emit their own accurate color, and that color bleeds onto nearby surfaces
• Reflective diamond/iron/gold/netherite blocks
• First-person metal tools and armor pick up a clean, non-ghosting reflection of
  the sky, ground, and sun that shifts naturally as you turn the camera

Weather & Underwater

• Rain darkens and cools the sky, thickens cloud cover, wets and darkens exposed
  surfaces, adds reflective sheen and raindrop ripples, and tints falling rain
• Underwater fog, caustics, edge refraction, and soft light shafts, each with its
  own strength control

Performance

• Everything above scales from the Fast preset up through Cinematic, with
  independent toggles for the heavier effects (caustics, light shafts, shadow
  resolution/distance) for players who want to tune their own balance