FeatherLite Shaders

FeatherLite V1 - Changelog
==========================

FeatherLite V1 is a major remake of FeatherLite Shaders v0.1
The pack was reworked from a realistic lighting style into a stylized one,
several long-standing bugs were fixed, and the cost per frame was reduced.

Based on FeatherLite Shaders v0.1 by resurrect5
Remake by AGAIN resurrect5 big props to myself lol.

NEW LOOK (stylized remake)
--------------------------
+ Soft 3-step toon lighting replaces smooth realistic gradients
+ Shadows shift toward cool purple-blue instead of just darkening
+ Warmer sun, blue-purple sky ambient, warm ground bounce
+ Stronger split toning: cool shadows, warm highlights
+ Higher color saturation (1.28) and saturated block colors
+ Subtle ink-style outline on silhouettes and depth edges, fading with
  distance (new option: OUTLINE_STRENGTH)
+ Vignette slightly stronger
+ Realism features turned off by default: normal bump, per-face tilt, sky
  reflection, wrap lighting; micro detail halved
+ Richer sky gradient: deeper blue overhead, lighter hazy horizon, faint warm
  horizon glow toward the sun
+ Slower, softer clouds (speed 0.35, coverage 0.55)

BUG FIXES
---------
* Shadows moving/sliding when walking or looking around
    World position was camera-relative but used as absolute, so shadow
    lookups, fog distance, lightning distance and per-block variation shifted
    with your position. Terrain, water, entity and weather vertex shaders now
    add cameraPosition. (Bug was present in v5.5.)
* Shadow map and lookup used different warps
    shadow.vsh now applies the same radial warp as the lookup. (Present in
    v5.5.)
* Leaves, grass and fences casting solid square shadows
    shadow.fsh was empty; it now discards transparent pixels (cutout alpha).
* Shadow acne (diagonal stripe patterns on leaves and terrain)
    Added a normal-offset bias scaled to the local shadow texel size.
* Shadow edge grain and crawling
    The dither was tied to screen pixels. The kernel is now a fixed pattern,
    and shadow taps were raised to 8 to keep edges smooth.
* Sky rotating against the camera
    The sky dome vertices skipped the camera rotation. They now go through the
    model-view matrix first.
* Flat navy slab below the horizon (very visible on low render distance)
    Replaced with a hazy horizon color that darkens naturally at night.
* Hard white cloud stripe at the horizon
    Clouds now fade out near the horizon and come in higher up.
* Grainy block textures
    Removed the fine per-pixel noise layer from block shading, lowered bump
    and face-variation strength, and the bump now uses the real atlas texel
    size instead of a hardcoded 1/256 step. Bump also fades out with distance
    and is clamped against high-contrast texels.
* Dark, flat lighting
    Higher ambient strength (0.90) and ambient floor, ambient no longer
    crushed under cover, sunlight can reach through leaf gaps, exposure 1.10,
    shadow darkening reduced, contrast reduced to stop crushing darks.

PERFORMANCE
-----------
Notes: these are design changes, not measured benchmarks. Test on your own
hardware.

+ Ambient occlusion skips its kernel on pixels beyond its range (the result
  was already faded to nothing there, so output is identical)
+ Coloured shadows off by default (they cost up to 3 texture reads per tap on
  shadowed pixels)
+ Normal bump off by default (saves 4 texture reads per fragment)
+ Bump fades out with distance (saves reads on far geometry)
+ Outline only runs within a limited distance, and shares the depth read used
  by AO
+ Bloom reuses its centre sample
+ Sun and moon directions computed once per fragment instead of 2-3 times
+ Shadow kernel and AO kernel reduced to 6 samples (shadow later raised to 8
  for quality; see fixes)
+ Godray sky test restored, unnecessary duplicate work removed
+ End galaxy is no longer drawn twice; END_COMPOSITE_OVERLAY (new option, off)
  re-enables the old overlay
+ Shadow distance 80 -> 72
+ New Ultra-Lite profile (AO, godrays, bloom, outline, ripples and frost off)

NEW OPTIONS
-----------
+ OUTLINE_STRENGTH       Ink outline strength (0 = off)
+ END_COMPOSITE_OVERLAY  Re-enable the old End galaxy composite overlay

CHANGED DEFAULTS
----------------
                    v5.5     V1
AMBIENT_STRENGTH    0.45     0.90
SUN_STRENGTH        1.20     1.05
TONEMAP_EXPOSURE    0.90     1.10
SATURATION          1.04     1.28
CONTRAST            1.12     1.10
SHADOW_TINT_AMOUNT  0.35     0.80
VIGNETTE            0.06     0.10
BUMP_STRENGTH       1.60     0.00
FACE_VARIATION      0.07     0.00
MICRO_DETAIL        0.80     0.50
SKY_FRESNEL         0.12     0.04
WRAP_LIGHTING       0.04     0.00
SHADOW_TAPS         8        8
AO_SAMPLES          8        6
GODRAYS_SAMPLES     8        6
SHADOW_COLORED      on       off
shadowDistance      80       72
CLOUD_COVERAGE      0.48     0.55
CLOUD_SPEED         0.75     0.35

TRIED AND REJECTED (during development)
---------------------------------------
- 2-tap texture bump: it looked equal on smooth ramps but measured about 50%
  gradient error on real block textures and leaned every normal toward the
  brighter side. Kept the 4-tap version.
- Cheaper hash-based replacements for underwater shimmer, micro detail, face
  variation, water waves, rain ripples and End sky layers: they caused visible
  artifacts (hard squares, grid edges, stripes, flatter water). Reverted.
- Godrays without the sky depth test: bright ground (snow, sand) cast rays.

KNOWN ISSUES
------------
- At low render distance the end of loaded terrain is still visible (game
  chunk limit). FOG_INTENSITY helps blend it.
- WET_GLOSS does nothing (inherited from v5.5)
- Night, rain, Nether, End and underwater have had less testing than daytime
  overworld
- Profiles set their own exposure and contrast, overriding the default values
- The block-bump option relies on Iris providing atlasSize; otherwise it
  assumes a 256px atlas

TECHNICAL
---------
- All shader stages validated with Khronos glslang (0 errors) after inlining
  Iris includes
- All options in shaders.properties checked against lib/settings.glsl
- Not benchmarked and not tested on a wide range of GPUs or Iris versions