float rand(vec2 x) {
    return fract(sin(dot(x, vec2(13.9898, 8.141))) * 43758.5453);
}

vec2 rand2(vec2 x) {
    return fract(sin(vec2(dot(x, vec2(13.9898, 8.141)),
						  dot(x, vec2(3.4562, 17.398)))) * 43758.5453);
}

vec3 rand3(vec2 x) {
    return fract(sin(vec3(dot(x, vec2(13.9898, 8.141)),
                          dot(x, vec2(3.4562, 17.398)),
                          dot(x, vec2(13.254, 5.867)))) * 43758.5453);
}

float sine(vec2 uv, float count, float sharpness) {
	return max(0.0, min(1.0, (0.5+sharpness*0.5*sin(count*3.1415928*2.0*uv.x))));
}

vec2 transform(vec2 uv, float rotate, float scale) {
	vec2 rv;
	uv -= vec2(0.5);
	rv.x = cos(rotate)*uv.x + sin(rotate)*uv.y;
	rv.y = -sin(rotate)*uv.x + cos(rotate)*uv.y;
	rv /= scale;
	rv += vec2(0.5);
	return rv;
}

float bricks(vec2 uv, vec2 count, float offset, float mortar, float bevel) {
	mortar /= max(count.x, count.y);
	bevel /= max(count.x, count.y);
	float fract_x = fract(uv.x*count.x+offset*step(0.5, fract(uv.y*count.y*0.5)));
	float slope_x = 1.0/(bevel*count.x);
	float off = 0.5*mortar/bevel;
	float f1 = fract_x*slope_x-off;
	float f2 = (1.0-fract_x)*slope_x-off;
	float fract_y = fract(uv.y*count.y);
	float slope_y = 1.0/(bevel*count.y);
	float f3 = fract_y*slope_y-off;
	float f4 = (1.0-fract_y)*slope_y-off;
	return max(0.0, min(1.0, min(min(f1, f2), min(f3, f4))));
}

float colored_bricks(vec2 uv, vec2 count, float offset) {
	float x = floor(uv.x*count.x+offset*step(0.5, fract(uv.y*count.y*0.5)));
	float y = floor(uv.y*count.y);
	return fract(x/3.0+y/7.0);
}

float perlin(vec2 uv, vec2 size, int iterations, float persistence, int seed) {
	uv += vec2(float(seed)*0.1234567);
    float rv = 0.0;
    float coef = 1.0;
    float acc = 0.0;
    for (int i = 0; i < iterations; ++i) {
    	vec2 step = vec2(1.0)/size;
        float f0 = rand(floor(fract(uv)*size));
        float f1 = rand(floor(fract(uv+vec2(step.x, 0.0))*size));
        float f2 = rand(floor(fract(uv+vec2(0.0, step.y))*size));
        float f3 = rand(floor(fract(uv+vec2(step.x, step.y))*size));
        vec2 mixval = fract(uv*size);
        mixval = 0.5*(1.0-cos(3.1415928*mixval));
        rv += coef * mix(mix(f0, f1, mixval.x), mix(f2, f3, mixval.x), mixval.y);
        acc += coef;
        size *= 2.0;
        coef *= persistence;
    }
    
    return rv / acc;
}

vec4 voronoi(vec2 uv, vec2 size, float intensity, int seed) {
	uv += vec2(float(seed)*0.1234567);
    uv *= size;
    float best_distance0 = 1.0;
    float best_distance1 = 1.0;
    vec2 point0;
    vec2 point1;
    vec2 p0 = floor(uv);
    for (int dx = -1; dx < 2; ++dx) {
    	for (int dy = -1; dy < 2; ++dy) {
            vec2 d = vec2(float(dx), float(dy));
            vec2 p = p0+d;
            p += rand2(mod(p, size));
            float distance = length((uv - p) / size);
            if (best_distance0 > distance) {
            	best_distance1 = best_distance0;
            	best_distance0 = distance;
                point1 = point0;
                point0 = p;
            } else if (best_distance1 > distance) {
            	best_distance1 = distance;
                point1 = p;
            }
        }
    }
    float edge_distance = dot(uv - 0.5*(point0+point1), normalize(point0-point1));
    
    return vec4(point0, best_distance0*length(size)*intensity, edge_distance);
}