star_map.gdshader

// Star Nest by Pablo Roman Andrioli
// Ported to Godot by Lyagva
// License: MIT
shader_type canvas_item;

uniform int iterations = 17;
uniform float formuparam = 0.53;

uniform int volsteps = 10;
uniform float stepsize = 0.1;

uniform float zoom   = 0.800;
uniform float tile   = 0.850;
uniform vec3  speed  = vec3(0.0, 3, 1);

uniform float brightness = 0.0015;
uniform float darkmatter = 0.300;
uniform float distfading = 0.730;
uniform float saturation = 0.850;

uniform vec2 rotation;
uniform sampler2D coloramp;
uniform float colorampMix = .5;
uniform bool isColoramp;

void fragment()
{
	vec2 fragCoord = FRAGCOORD.xy;
	vec2 iResolution = 1.0 / SCREEN_PIXEL_SIZE;

	//get coords and direction
	vec2 uv=fragCoord.xy/iResolution.xy-.5;
	uv.y*=iResolution.y/iResolution.x;
	vec3 dir=vec3(uv*zoom,1.);
	vec3 time=vec3(speed * TIME * 0.001);

	//mouse rotation
	float a1 = .5 + rotation.x / iResolution.x * 2.;
	float a2 = .8 + rotation.y / iResolution.y * 2.;
	mat2 rot1 = mat2(vec2(cos(a1), sin(a1)), vec2(-sin(a1), cos(a1)));
	mat2 rot2 = mat2(vec2(cos(a2), sin(a2)), vec2(-sin(a2), cos(a2)));
	dir.xz *= rot1;
	dir.xy *= rot2;
	vec3 from = vec3(1.,.5,0.5);
	from += time;
	from.xz *= rot1;
	from.xy *= rot2;

	//volumetric rendering
	float s = 0.1, fade = 1.;
	vec3 v=vec3(0.);
	for (int r=0; r<volsteps; r++) {
		vec3 p=from+s*dir*.5;
		p = abs(vec3(tile)-mod(p,vec3(tile*2.))); // tiling fold
		float pa,a=pa=0.;
		for (int i=0; i<iterations; i++) {
			p=abs(p)/dot(p,p)-formuparam; // the magic formula
			a+=abs(length(p)-pa); // absolute sum of average change
			pa=length(p);
		}
		float dm=max(0.,darkmatter-a*a*.001); //dark matter
		a*=a*a; // add contrast
		if (r>6) fade*=1.-dm; // dark matter, don't render near
		//v+=vec3(dm,dm*.5,0.);
		v+=fade;
		v+=vec3(s,s*s,s*s*s*s)*a*brightness*0.01*fade; // coloring based on distance
		fade*=distfading; // distance fading
		s+=stepsize;
	}
	v=mix(vec3(length(v)),v,saturation); //color adjust

	COLOR = vec4(v*.01,1.);

	if (isColoramp) {
		COLOR += texture(coloramp, vec2(v.r * .01, 0.)) * colorampMix;
	}

}