Hard Effects

Four-way mirrored polar stripes with a dark vignette

A picture built in steps: mirror both ways, then polar coordinates, then draw stripes, then color it, then finish with a dark vignette. Every step is listed below with its exact numbers.

The target picture for the shader challenge "Four-way mirrored polar stripes with a dark vignette"
Recreate this picture. You pass at a 99% match, then try to write it in fewer characters than the par.

How this challenge works

You write a fragment shader that draws the picture above, live in your browser. A match bar shows how close you are, and the score combines accuracy, code size (the par is 398 characters in Unity (Built-in)) and GPU speed. Work in HLSL, GLSL, WGSL, Metal or Godot and export the result when you are done.

The numbers you need

Space
p = (uv - 0.5) * float2(aspect, 1.0)
Step 1: Mirror both ways
p = abs(p)
Step 2: Polar coordinates
p = float2(atan2(p.y, p.x) / 3.1415927, length(p) * 2.0) (x = angle from -1 to 1, y = distance)
Step 3: Pattern
m = step(0.55, frac(dot(p, float2(1.0, -1.0)) * 5.0))
Step 4: Colors
lerp(float3(0.73, 0.18, 0.6), float3(0.22, 0.81, 0.21), m)
Step 5: Finish
col *= 1.0 - 0.6 * smoothstep(0.3, 0.85, length(s)), s = (uv - 0.5) * float2(aspect, 1.0)

Solve it in your language

Unity (Built-in), Unity (URP), Unreal, Shadertoy / WebGL, OpenGL (LWJGL, raylib), three.js, GameMaker, LÖVE (Lua), Godot, Apple (iOS, macOS), WebGPU / Bevy.

Start coding