---

/*{
	"CREDIT": "mojovideotech",
	"CATEGORIES": [
		""
	],
	"DESCRIPTION": "",
	"INPUTS": [
		{
			"MAX": [
				3,
				3
			],
			"MIN": [
				-3,
				-3
			],
			"NAME": "mouse",
			"TYPE": "point2D"
		},
		{
			"NAME": "rate",
			"TYPE": "float",
			"DEFAULT": 67,
			"MIN": 0.5,
			"MAX": 100
		},
		{
			"NAME": "zoom",
			"TYPE": "float",
			"DEFAULT": 0.84,
			"MIN": -3,
			"MAX": 3
		},
		{
			"NAME": "offset1",
			"TYPE": "float",
			"DEFAULT": -31,
			"MIN": -100,
			"MAX": 100
		},
		{
			"NAME": "density",
			"TYPE": "float",
			"DEFAULT": 4,
			"MIN": 1,
			"MAX": 18
		},
		{
			"NAME": "width",
			"TYPE": "float",
			"DEFAULT": 0.03,
			"MIN": 0.0025,
			"MAX": 0.125
		}
	]
}
*/

// SpiderSpectre by mojovideotech

#ifdef GL_ES
precision mediump float;
#endif

#define twpi  6.2831853


float line(vec2 p, vec2 a, vec2 b)
{
	if(a == b) return 0.;
	float d = distance(a, b);
	vec2  n = normalize(b - a);
    vec2  l = vec2(0.);
	p	-= a;
	d	*= -.5;
	l.x = fract(dot(p, vec2(-n.y, n.x)));
	l.y = fract(dot(p, n.xy)+d)+d;
	l 	= max(l, 0.);
	return  1.-clamp(dot(RENDERSIZE * width, l), 0., 1.);
}

mat2 rmat(float t)
{
    float c = cos(t);
    float s = sin(t-c);
    return mat2(c,s,-s,c);
}

void main( void ) {
    float T = TIME/(100.-rate);
	vec2 uv = (isf_FragNormCoord.xy)*zoom;
	vec2 p 	= (uv * 2. - mouse) * RENDERSIZE.xy/RENDERSIZE.yy;
	vec2 m  = (sin(T)*twpi) * 2. - mouse * RENDERSIZE.xy/RENDERSIZE.yy;
	float h = 0., k = 0., j = 0.;

	for(int i = 0; i <36; i++)
	{
		float dn = density*2. + 1.;
        int bpc = int(floor(dn));
           bpc -= i;
        if (bpc<1) break;
		h += line(uv,-p,sin(m));
		k += line(uv,cos(p),m);
		j += line(cos(m),p,uv);
     	p *= rmat(float(bpc-i)*atan(m.x*offset1)*cos(m.y/offset1));
	}

        vec4 g = vec4(vec3(length(p),0.5,0.5),1);
        gl_FragColor = vec4(j-h+k, k+h-j, j+h-k, 1.0) * g;
}