// Taken from https://www.shadertoy.com/view/lsSGzy
//Flaring by nimitz (twitter: @stormoid)

//change this value (1 to 5) or tweak the settings yourself.
//the gamma and spot brightness parameters can use negative values
#define TYPE 4

#if TYPE == 1
	#define brightness 1.
	#define ray_brightness 11.
	#define gamma 5.
	#define spot_brightness 4.
	#define ray_density 1.5
	#define curvature .1
	#define red   7.
	#define green 1.3
	#define blue  1.
	//1 -> ridged, 2 -> sinfbm, 3 -> pure fbm
	#define noisetype 2
	#define sin_freq 50. //for type 2
#elif TYPE == 2
	#define brightness 1.5
	#define ray_brightness 10.
	#define gamma 8.
	#define spot_brightness 15.
	#define ray_density 3.5
	#define curvature 15.
	#define red   4.
	#define green 1.
	#define blue  .1
	#define noisetype 1
	#define sin_freq 13.
#elif TYPE == 3
	#define brightness 1.5
	#define ray_brightness 20.
	#define gamma 4.
	#define spot_brightness .95
	#define ray_density 3.14
	#define curvature 17.
	#define red   2.9
	#define green .7
	#define blue  3.5
	#define noisetype 2
	#define sin_freq 15.
#elif TYPE == 4
	#define brightness 3.
	#define ray_brightness 5.
	#define gamma 6.
	#define spot_brightness 1.5
	#define ray_density 6.
	#define curvature 90.
	#define red   1.8
	#define green 3.
	#define blue  .5
	#define noisetype 1
	#define sin_freq 6.
	#define YO_DAWG
#elif TYPE == 5
	#define brightness 2.
	#define ray_brightness 5.
	#define gamma 5.
	#define spot_brightness 1.7
	#define ray_density 30.
	#define curvature 1.
	#define red   1.
	#define green 4.0
	#define blue  4.9
	#define noisetype 2
	#define sin_freq 5. //for type 2
#endif


//#define PROCEDURAL_NOISE
//#define YO_DAWG


float hash( float n ){return fract(sin(n)*43758.5453);}

float noise( in vec2 x )
{
	#ifdef PROCEDURAL_NOISE
	x *= 1.75;
    vec2 p = floor(x);
    vec2 f = fract(x);

    f = f*f*(3.0-2.0*f);

    float n = p.x + p.y*57.0;

    float res = mix(mix( hash(n+  0.0), hash(n+  1.0),f.x),
                    mix( hash(n+ 57.0), hash(n+ 58.0),f.x),f.y);
    return res;
	#else
	return texture(iChannel0, x*.01).x;
	#endif
}

mat2 m2 = mat2( 0.80,  0.60, -0.60,  0.80 );
float fbm( in vec2 p )
{
	float z=2.;
	float rz = 0.;
	p *= 0.25;
	for (float i= 1.;i < 6.;i++ )
	{
		#if noisetype == 1
		rz+= abs((noise(p)-0.5)*2.)/z;
		#elif noisetype == 2
		rz+= (sin(noise(p)*sin_freq)*0.5+0.5) /z;
		#else
		rz+= noise(p)/z;
		#endif
		z = z*2.;
		p = p*2.*m2;
	}
	return rz;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
	float t = -iTime*0.03;
	vec2 uv = fragCoord.xy / iResolution.xy-0.5;
	uv.x *= iResolution.x/iResolution.y;
	uv*= curvature*.05+0.0001;

	float r  = sqrt(dot(uv,uv));
	float x = dot(normalize(uv), vec2(.5,0.))+t;
	float y = dot(normalize(uv), vec2(.0,.5))+t;

	#ifdef YO_DAWG
	x = fbm(vec2(y*ray_density*0.5,r+x*ray_density*.2));
	y = fbm(vec2(r+y*ray_density*0.1,x*ray_density*.5));
	#endif

    float val;
    val = fbm(vec2(r+y*ray_density,r+x*ray_density-y));
	val = smoothstep(gamma*.02-.1,ray_brightness+(gamma*0.02-.1)+.001,val);
	val = sqrt(val);

	vec3 col = val/vec3(red,green,blue);
	col = clamp(1.-col,0.,1.);
	col = mix(col,vec3(1.),spot_brightness-r/0.1/curvature*200./brightness);

	fragColor = vec4(col,1.0);
}
