varying vec2 UV;

uniform sampler2D myTextureSampler;
uniform sampler2D myTextureSampler2;
uniform float transitionTime;

float rand(float n) {
    return fract(sin(n) * 43758.5453123);
}

void main() {
	float tileMulti = 2.0;
	float randomness = 0.1;
    float tileIndex = 89.2*floor( UV.x * 16.0 * tileMulti)
        + 179.1*floor( UV.y * 9.0 * tileMulti);
    float tileDelta = rand(tileIndex)*randomness - randomness / 2.0;
    float x = -1.0 - randomness / 2.0 + UV.x + transitionTime * (1.0 + 1.0 + randomness);
    float tileColor = smoothstep(0.0, 1.0, clamp(x + tileDelta, 0.0, 1.0));
    gl_FragColor = texture2D( myTextureSampler, UV ) * (1.0 - tileColor)
                 + texture2D( myTextureSampler2, UV ) * tileColor;
    //gl_FragColor = vec4(tileColor, tileColor, tileColor, 1.0);
}