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Iridescent oil slick from thin-film interference

In your harnessProcedural textureMIT

Generate tileable maps of thin-film interference colours: oil on puddles in asphalt, a spill on harbour water, a soap film or heat tint on steel, with colours computed from film thickness, refractive indices and colour-matching functions. Use for wet streets, polluted water, bubbles and welded metal.

Render of Iridescent oil slick from thin-film interference
The render its check recorded in Godot 4.7.2, 256 by 256 pixels.

What it takes and gives

Entry point
generate
Maps
albedo, normal, roughness, metallic, height, ao
Parameters
pattern, film_min, film_max, scale, swirl, coverage, vividness, hue_shift and 2 more
Presets
default, harbour_water, soap_film, tempered_steel
Tileable
yes
Command line
python oil_slick_iridescent.py --size 1024 --seed 7 --preset NAME --out DIR [--width W --height H] [--set NAME=VALUE] [--directx-normal] [--orm]
Godot material
material.tres
Blender builder
blender_material.build_material(folder)

Limits. Two-beam interference at normal incidence: colours do not shift with viewing angle, multiple reflections and absorption are ignored, and a metal substrate is approximated by a negative real reflection amplitude instead of a complex index, so temper colours are close but not exact. The colour-matching functions are an analytic Gaussian fit and the grey part of the film reflectance is partly removed for clearer hues, so this is a stylized rendering of thin-film colour rather than a spectral measurement. Film thickness comes from noise or bands, not from flow or oxidation physics. One still frame.

Details

Kind
Procedural texture
Engine
Python 3.10 or later
Files
12 files, 258.7 KB
Licence
MIT
Declared effects
runs commands, writes files
Checked with
Godot 4.7.2, gl_compatibility
Checks
command line generates declared maps, maps decode, maps have declared size and channels, maps tile without a seam, normal vectors unit length facing out, maps carry detail, godot imports the maps, godot material template loads every map, godot compatibility render, capture shows the textured surface, blender builds the material
Techniques
Two-beam thin-film interference with Fresnel amplitudes at normal incidence, Spectral integration against a multi-lobe Gaussian fit of the CIE 1931 colour-matching functions, CIE XYZ to linear sRGB conversion, Domain-warped fractional Brownian motion for film thickness, Puddles from flooding an asphalt height field to a quantile level, Height to tangent-space normal by central differences
Tags
texture, pbr, tileable, iridescent, oil, thin film, puddle, heat tint
Identity
library.supply.creative_originals.438e4b09edf4fddd5d5c7cd0.b0d5a4fe3cf9a5a1
Version
b0d5a4fe3cf9a5a1767d7d252fe652977d452893b479f452e45ec909ffdc86c4

The version is the SHA-256 of the item your harness downloads; every file in it names its own checksum.

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