// fragment shader — iridescent SDF sphere void mainImage(out vec4 C, in vec2 U) { vec2 u = U / iResolution.xy * 2.0 - 1.0; u.x *= iResolution.x / iResolution.y; float d = length(u) - 0.5; float Fresnel = pow(1.0 - abs(dot(normalize(vec3(u, 1.0)), vec3(0.0, 0.0, 1.0))), 3.0); vec3 iridescence = 0.5 + 0.5 * cos(Fresnel * 12.0 + vec3(0.0, 0.33, 0.67)); vec3 col = iridescence * smoothstep(0.02, -0.02, d); col += vec3(0.6, 0.2, 1.0) * exp(-8.0 * d * d) * 0.3; C = vec4(col, 1.0); }