precision highp float;

varying vec2 textureCoordinate;
uniform sampler2D from;
uniform sampler2D to;
uniform float progress;

vec4 getFromColor(vec2 uv) {
    return texture2D(from,uv);
}

vec4 getToColor(vec2 uv){
    return texture2D(to,uv);
}

float size = 0.2;

float rand (vec2 co) {
    return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}

vec4 transition (vec2 uv) {
    float r = rand(vec2(0, uv.y));
    float m = smoothstep(0.0, -size, uv.x*(1.0-size) + size*r - (progress * (1.0 + size)));
    return mix(
               getFromColor(uv),
               getToColor(uv),
               m
               );
}
void main(){
    gl_FragColor = transition(textureCoordinate);
    }