Seamless Perlin Noise

A seamless and tileable version of the Perlin Noise. Use this as is or as noise in the Fractal Brownian Motion function. cell_amount and period together sets how many times (and thus the appeared size) the noise will tile within the texture.

uniform int cell_amount = 20;
uniform vec2 period = vec2(5., 10.);

vec2 modulo(vec2 divident, vec2 divisor){
	vec2 positiveDivident = mod(divident, divisor) + divisor;
	return mod(positiveDivident, divisor);
}

vec2 random(vec2 value){
	value = vec2( dot(value, vec2(127.1,311.7) ),
				  dot(value, vec2(269.5,183.3) ) );
	return -1.0 + 2.0 * fract(sin(value) * 43758.5453123);
}

float seamless_noise(vec2 uv, vec2 _period) {
	uv = uv * float(cell_amount);
	vec2 cellsMinimum = floor(uv);
	vec2 cellsMaximum = ceil(uv);
	vec2 uv_fract = fract(uv);
	
	cellsMinimum = modulo(cellsMinimum, _period);
	cellsMaximum = modulo(cellsMaximum, _period);
	
	vec2 blur = smoothstep(0.0, 1.0, uv_fract);
	
	vec2 lowerLeftDirection = random(vec2(cellsMinimum.x, cellsMinimum.y));
	vec2 lowerRightDirection = random(vec2(cellsMaximum.x, cellsMinimum.y));
	vec2 upperLeftDirection = random(vec2(cellsMinimum.x, cellsMaximum.y));
	vec2 upperRightDirection = random(vec2(cellsMaximum.x, cellsMaximum.y));
	
	vec2 fraction = fract(uv);
	
	return mix( mix( dot( lowerLeftDirection, fraction - vec2(0, 0) ),
                     dot( lowerRightDirection, fraction - vec2(1, 0) ), blur.x),
                mix( dot( upperLeftDirection, fraction - vec2(0, 1) ),
                     dot( upperRightDirection, fraction - vec2(1, 1) ), blur.x), blur.y) * 0.8 + 0.5;
}

void fragment(){
	float noise = seamless_noise(UV, period);
	COLOR.rgb = vec3(noise);
}

This method of making a seamless noise is a modified version of Ronja’s tileable perlin noise.