Godot-Shader-Lib/addons/ShaderLib/Procedural/Noise/SimpleNoise.gdshaderinc

float noise_random_value(vec2 uv){
	return fract(sin(dot(uv, vec2(12.9898, 78.233))) * 43758.5453);
}

float noise_interpolate(float a, float b, float t){
	return (1.0 - t) * a + (t * b);
}

float value_noise(vec2 uv){
	vec2 i = floor(uv);
	vec2 f = fract(uv);
	f = f * f * (3.0 - 2.0 * f);
	uv = abs(fract(uv) - 0.5);
	
	vec2 c0 = i + vec2(0.0, 0.0);
	vec2 c1 = i + vec2(1.0, 0.0);
	vec2 c2 = i + vec2(0.0, 1.0);
	vec2 c3 = i + vec2(1.0, 1.0);
	
	float r0 = noise_random_value(c0);
	float r1 = noise_random_value(c1);
	float r2 = noise_random_value(c2);
	float r3 = noise_random_value(c3);
	
	float bottom_of_grid = noise_interpolate(r0, r1, f.x);
	float top_of_grid = noise_interpolate(r2, r3, f.x);
	float t = noise_interpolate(bottom_of_grid, top_of_grid, f.y);
	
	return t;
}

float simple_noise(vec2 uv, float scale){
	float t = 0.0;
	float freq = pow(2.0, float(0));
	float amp = pow(0.5, float(3-0));
	
	t += value_noise(vec2(uv.x * scale / freq, uv.y * scale / freq)) * amp;
	freq = pow(2.0, float(1));
	amp = pow(0.5, float(3-1));
	
	t += value_noise(vec2(uv.x * scale / freq, uv.y * scale / freq)) * amp;
	freq = pow(2.0, float(2));
	amp = pow(0.5, float(3-2));
	
	t += value_noise(vec2(uv.x * scale / freq, uv.y * scale / freq)) * amp;
	return t;
}