Stationary star skybox 3D

This shader separates the skybox sphere into sections of roughly similar area. Then it draws a star in each section to obtain a uniform distribution of stars.

Shader code

shader_type sky;

uniform int vertical_sections = 21;
uniform float star_size = 0.02;
uniform float star_falloff = 4.;
uniform float margin = 0.05; // How far the star is from the edge of it's section. Avoids artifacts at the edge of sections.

vec2 get_partition(vec2 sky_coords) {
	// Separate the sphere into sections of roughly equal width and height.
	float y = sky_coords.y * 2. - 1.;
	float section_y = ceil(abs(y) * float(vertical_sections)) / float(vertical_sections);
	float horizontal_sections = max(4., ceil(float(vertical_sections) * 4. * cos(section_y * PI / 2.)));
	horizontal_sections = horizontal_sections > 0. ? horizontal_sections : 1.;
	return vec2(sky_coords.x * horizontal_sections, y * float(vertical_sections));
}

vec2 rand_vec2(vec2 xy) {
    float rand1 = fract(sin(dot(xy, vec2(11.9131, 81.2317))) *  57183.77193);
    float rand2 = fract(sin(dot(xy, vec2(16.8131, 91.2327))) *  37113.66193);
	return vec2(rand1, rand2) * ( 1. - margin * 2.) + margin;
}

float star_brightness(vec2 sky_coords) {
	vec2 partitions = get_partition(sky_coords);
	vec2 partition_index = floor(partitions);
	vec2 inner_coord = fract(partitions);
	vec2 star_coord = rand_vec2(partition_index);
	float dist = length(inner_coord - star_coord);
	return pow(star_size / dist, star_falloff);
}

void sky() {
	COLOR = vec3(star_brightness(SKY_COORDS));
}

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