perlin.glsl

#version 140
precision mediump float;

uniform float time;

float rand(vec2 co){
  	return fract(sin(dot(co, vec2(12.9898, 78.233))) * 43758.5453)*100.0;
}

vec2 getblock(float res, vec2 loc) {

	vec2 block = floor((loc) / res)*res;

  	return block;
}

vec2 getVector(bool animate, float res, vec2 loc) {

	float block = rand(getblock(res, loc))*100.0;
	float rotSpeed = time*(sin(block)/10.0);

	if (!animate) {
		rotSpeed = 0.0;
	}

  	return vec2(sin(block+rotSpeed),cos(block+rotSpeed));
}

float interpolate(float t) {
	return 6.0*pow(t,5.0)-15.0*pow(t,4.0)+10.0*pow(t,3.0);
}

float perlin(bool animate, float res, vec2 loc) {

	vec2 localCoord = (getblock(res, loc+res)-loc)/res;

	vec2 vecTL = getVector(animate, res, loc);
	vec2 vecTR = getVector(animate, res, loc+vec2(res,0));
	vec2 vecBL = getVector(animate, res, loc+vec2(0,-res));
	vec2 vecBR = getVector(animate, res, loc+vec2(res,-res));

	vec2 interp = vec2(interpolate(localCoord.x),interpolate(localCoord.y));

	// Map range from 0 - 1 to -1 - 1
	localCoord = localCoord*2.0-1.0;

	float dottl = (dot(vecTL, localCoord-vec2(1.0,-1.0))+1.4)/2.3;
	float dottr = (dot(vecTR, localCoord-vec2(-1.0,-1.0))+1.4)/2.3;
	float dotbl = (dot(vecBL, localCoord-vec2(1.0,1.0))+1.4)/2.3;
	float dotbr = (dot(vecBR, localCoord-vec2(-1.0,1.0))+1.4)/2.3;

  	float horizTop = interp.x*dottl+(1.0-interp.x)*dottr;
  	float horizBottom = interp.x*dotbl+(1.0-interp.x)*dotbr;

  	float vertical = interp.y*horizBottom+(1.0-interp.y)*horizTop;

	return vertical/1.2;
}

float perlin(vec2 offset) {
	float res = 140.0;
  	float movementAmount = 1000.0; // Higher
  	float movementSpeed = 30.0; // Lower

  	float rand1 = perlin(false, movementSpeed, vec2(offset.x+time))*movementAmount;
  	float rand2 = perlin(false, movementSpeed, vec2(offset.x+time+500000.0))*movementAmount;

	float perlin1 = perlin(true, res, 1.0*(offset+gl_FragCoord.xy+vec2(rand1, rand2)))/1.0;
  	float perlin2 = perlin(true, res, 4.0*(offset+gl_FragCoord.xy+vec2(rand1, rand2)))/16.0;
  	//float perlin3 = perlin(true, res, 0.2*(gl_FragCoord.xy+vec2(rand1, rand2)))*3.0;

  	return (perlin1 + perlin2)/(1.0 + 1.0/16.0);
}

void main(void) {
	float value = perlin(vec2(0));
	float value2 = perlin(vec2(3402.324));

	float fract = fract(value*value2*10.0)/5.0;
	gl_FragColor = vec4(vec3(fract), 1.0);
}