AdaptiveDistributedRenderScene()

void adaptive_distributed_render_scene(
   double HalfWidth,double HalfHeight,
   int   nx,int ny,int nxSub,int nySub,
   double Variance,
   char *PicFileName)
{
   double x,y;                // sample point
   ray   ray;                 // pixel ray
   double hx = 2.0   * HalfWidth / nx;   // pixel width
   double hy = 2.0   * HalfHeight / ny;     // pixel height
   double hxSub = hx /  nxSub;
   double hySub = hy /  nySub;
   double Disp;               // dispersion squared
   int   i,j;
   Vector Color;
   Vector Sum;
   Vector Mean;
   int   Count;

   // make  next in  some higher-level module as: RenderOutFile = new Targa...
   targa_image *tga = new targa_image(PicFileName, nx, ny);
   rgb   c;

   for(i = 0, y = HalfHeight; i < ny; i++, y -= hy)
   {
      for(j = 0, x = -HalfWidth; j < nx; j++, x += hx)
      {
         double x1 = x - 0.5 * hx;
         double y1 = y - 0.5 * hy;
         double d;

         Sum   = 0;
         Disp  = 0;
         Count = 0;

         TotalPixels++;

         do {
            for(int  iSub = 0; iSub < nxSub; iSub++)
               for(int  jSub = 0; jSub < nySub; jSub++)
               {
                  camera(x1+hxSub*(iSub+rnd()),y1+hySub*(jSub+rnd()),ray);
                  Color =  trace( air, 1.0, ray );
                  Sum   += Color;
                  Disp +=  Color &  Color;
                  Count++;
               }
            Mean = Sum / Count;
            d =   (Disp /  Count -  (Mean &  Mean)) * Count / (Count - 1);
         } while(d / Count >= Variance && Count < 99);

         clip( Mean );
         c.r   = Mean.x * 255;
         c.g   = Mean.y * 255;
         c.b   = Mean.z * 255;

         tga->put_pixel(   c );
      }
   }

   delete tga;
}

https://github.com/berkus/grayzer/blob/master/src/render/ADRender.cpp
и пример использования https://github.com/berkus/grayzer/blob/master/examples/exampleA/exampleA.cpp