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

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

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

// From http://lolengine.net/blog/2013/07/27/rgb-to-hsv-in-glsl
vec3 rgb2hsv(vec3 c) {
	vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
	vec4 p = c.g < c.b ? vec4(c.bg, K.wz) : vec4(c.gb, K.xy);
	vec4 q = c.r < p.x ? vec4(p.xyw, c.r) : vec4(c.r, p.yzx);

	float d = q.x - min(q.w, q.y);
	float e = 1.0e-10;
	return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
}

vec3 hsv2rgb(vec3 c) {
	vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
	vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
	return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
}

uniform float envelope_time = 1.0;