kernel SuperNova
{
  const float width = 1000.0;
  const float height = 1000.0;
  const float2 center = { width/2.0, height/2.0 };
  const float PI = 3.14159265;
  const float4 color1 = { 0.1, 0.1, 0.2, 1.0 };
  const float4 color2 = { 0.2, 0.2, 0.4, 1.0 };
  const float4 colorCenter = { 0.9, 0.9, 1.0, 1.0 };
  const float phase = 30.0;
  const float radius = 20.0;
  const float color2radius = 10.0;
  float length( float2 v)
  {
    v *= v;
    return sqrt( v[0] + v[1] );
  }
  
  void evaluatePixel(out pixel4 result)
  {
    float2 vec = result.coord - center;
    float vec_length = length( vec );
    float angle = atan2( vec.x, vec.y);
    float coef = 0.9 * (cos( angle * phase) * cos( angle * 0.5 * phase ) * cos( angle * 0.1 * phase ) * cos( angle * 0.01 * phase )) + 0.1;
    if( coef < 0.0 ) coef = - coef;
    float adjRadius = radius  * ( 1.0 + 2.0 * coef ); //( 0.5 + 0.5 * cos(angle) );
    if( vec_length > adjRadius )
    {
      if( vec_length < adjRadius )
      {
	coef = pow((radius - vec_length) / adjRadius , 1.0 ) * ( 1.0 - coef) + coef;
      }
      float coef2 = 1.0;
      if( vec_length < color2radius * radius )
      {
	coef2 = (vec_length - radius) / ( (color2radius - 1.0) * radius );
      }
      result = ( 1 - coef ) * (  coef2 * color1 + (1 - coef2) *  color2) + coef * colorCenter;
      
      for( int i = 0; i < 3; ++i)
      {
	if(result[i] < 0) result[i] = 0.0;
	else if(result[i] > 1) result[i] = 1.0;
      }
      result[3] = 1.0;
    } else {
      result = colorCenter;
    }
  }
  region generated()
  {
    region reg = { 0, 0, width, height};
    return reg;
  }
}