src/react-fluid-distortion/glsl/composite.frag

uniform sampler2D tFluid;

uniform vec3 uColor;
uniform vec3 uBackgroundColor;

uniform float uDistort;
uniform float uIntensity;
uniform float uRainbow;
uniform float uBlend;
uniform float uShowBackground;

void mainImage(const in vec4 inputColor, const in vec2 uv, out vec4 outputColor) {

    vec3 fluidColor = texture2D(tFluid, uv).rgb;

    vec2 distortedUv = uv - fluidColor.rg * uDistort * 0.001;

    vec4 texture = texture2D(inputBuffer, distortedUv);

    float intensity = length(fluidColor) * uIntensity * 0.0001;

    vec3 selectedColor = uColor * length(fluidColor);

    vec4 colorForFluidEffect = vec4(uRainbow == 1.0 ? fluidColor : selectedColor, 1.0);

    vec4 computedBgColor = uShowBackground != 0.0 ? vec4(uBackgroundColor, 1.0) : vec4(0.0, 0.0, 0.0, 0.0);

    outputColor = mix(texture, colorForFluidEffect, intensity);

    vec4 computedFluidColor = mix(texture, colorForFluidEffect, uBlend * 0.01);

    vec4 finalColor;

    if(texture.a < 0.1) {
        finalColor = mix(computedBgColor, colorForFluidEffect, intensity);
    } else {
        finalColor = mix(computedFluidColor, computedBgColor, 1.0 - texture.a);
    }

    outputColor = finalColor;
}