/* credits to: TheTimJames 
   https://www.shadertoy.com/view/Md2GRw
*/

#include "shaders_common.h"

static const char* stock_fragment_xmb_snowflake = GLSL(
   uniform float time;
   uniform float atime;
   uniform vec2 OutputSize;
   vec2 uv;

   float rand(vec2 co)
   {
      return fract(sin(dot(co.xy, vec2(12.9898, 78.233))) * 43758.5453);
   }

   float snow(vec3 pos, vec2 uv, float o)
   {
      vec2 d = (pos.xy - uv);
      float a = atan(d.y,d.x)+sin(atime*1.+o)*10.;
      
      float dist = d.x*d.x + d.y*d.y;
      
      if(dist < pos.z/400.){
         float col = 0.0;
         if(sin(a*8.) < 0.0){col=1.0;}
         if(dist<pos.z/800.0){col+=1.0;}
         return col*pos.z;
      }
      
      return 0.0;
   }

   float col(vec2 c)
   {
      float color = 0.0;
      for (int i = 1; i < 15; i++)
      {
		   float o = rand(float(i) / 3.) * 15 * 2.0;
		   float z = rand(float(i) + 13.0);
		   float x = 1.8 - (3.6) * (rand(floor((time*((z+1.0)/2.0)+o)/2.0)) + sin(time*o/1000.0)/10.0);
		   float y = 1.0-mod((time*((z+1.0)/2.0))+o, 2.0);
		
		   color += snow(vec3(x,y,z),c,o);    
	   }


	
      return color;
   } 

   void main(void)
   {
      uv = gl_FragCoord.xy / OutputSize.xy;
      uv = uv * 2.0 - 1.0;
      vec2 p = uv;
      p.x *= OutputSize.x / OutputSize.y;
      
      atime = (time + 1)/4.0;
	
      gl_FragColor = vec4(col(p));
   }

);