// Author: Travis Fischer
// License: MIT
// Description: A crossfade in which a displacement map (an extra grayscale texture) warps both images
// Tags: displace, distort, blend
//
// Adapted from a Codrops article by Robin Delaporte
// https://tympanus.net/Development/DistortionHoverEffect

uniform sampler2D displacementMap;

// @param Strength of the displacement
uniform float strength; // = 0.5

vec4 transition (vec2 uv) {
  float displacement = texture2D(displacementMap, uv).r * strength;

  vec2 uvFrom = vec2(uv.x + progress * displacement, uv.y);
  vec2 uvTo = vec2(uv.x - (1.0 - progress) * displacement, uv.y);

  return mix(
    getFromColor(uvFrom),
    getToColor(uvTo),
    progress
  );
}