star_nest.glsl Full Listing

star_nest.glsl

// Star Nest by Pablo Roman Andrioli
// This content is under the MIT License.
// Source : https://www.shadertoy.com/view/XlfGRj

#define iterations 17
#define formuparam 0.53

#define volsteps 20
#define stepsize 0.1

#define zoom   0.800
#define tile   0.850
#define speed  0.010

#define brightness 0.0015
#define darkmatter 0.300
#define distfading 0.730
#define saturation 0.850

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    //get coords and direction
    vec2 uv=fragCoord.xy/iResolution.xy-.5;
    uv.y*=iResolution.y/iResolution.x;
    vec3 dir=vec3(uv*zoom,1.);
    float time=iTime*speed+.25;

    //mouse rotation
    float a1=.5+iMouse.x/iResolution.x*2.;
    float a2=.8+iMouse.y/iResolution.y*2.;
    mat2 rot1=mat2(cos(a1),sin(a1),-sin(a1),cos(a1));
    mat2 rot2=mat2(cos(a2),sin(a2),-sin(a2),cos(a2));
    dir.xz*=rot1;
    dir.xy*=rot2;
    vec3 from=vec3(1.,.5,0.5);
    from+=vec3(time*2.,time,-2.);
    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*fade; // coloring based on distance
        fade*=distfading; // distance fading
        s+=stepsize;
    }
    v=mix(vec3(length(v)),v,saturation); //color adjust
    fragColor = vec4(v*.01,1.);
}