/*
 *****************************************************************************
 * Author: David S. Ebert                                                    *
 *****************************************************************************
 * This software was developed as part of on going research in the CIS       *
 * department at The Ohio State University. Any derivative of this code must *
 * credit the original author, The Ohio State University and must leave this *
 * paragraph unaltered.                                                      *
 *****************************************************************************
 */

#include   <stdio.h>
#include   <edge.h>
void my_dither();

 /************************************************************************
  *                    SCAN CONVERT THE OBJECT                           *
  ************************************************************************/

scan_them(e_w, face_ptr, ymin, ymax, size_polys, intensity)
     edge_td *e_w;
     xyz_td  *face_ptr;
     /* edge_td       *buffer; */
     int      ymin,ymax;
     long     size_polys;
     int      intensity;
 {
   xyzw_td       edge[20];
   int            k;
   double        z, zl, zr, dz, xr, xl, xlc, *z_buffer;
   double        *x_coord, *z_coord;
   long          yline, num_inter, x1;
   int           y_screen;

    z_coord = (double *)malloc(sizeof(double)*20);
    x_coord = (double *)malloc(sizeof(double)*20);    
    
    /*    calc distance between 2 pixels */
     

 for(yline=ymax; yline>ymin; yline--)
   { 
     intersect_scan_line(&num_inter,z_coord,x_coord,(int)yline,edge,
			 size_polys, face_ptr);
     /*  sort the intersections  */
     sort(x_coord,z_coord,edge,num_inter);           
     
     for(k=0; k < num_inter/2; k++)
       {
	   xl = x_coord[k*2];
	   xlc = xl;
	   ceiling(&xlc);
	   xr = (double) ((int)(x_coord[k*2+1]));
	     
	   for(x1=xlc; x1<=xr; x1++)
	     {
		 my_dither(e_w, (int)x1, (int)yline, intensity);
		 /* edge_plotpoint(e_w, x1, (int)yline);*/
		 /* draw it into the frame_buffer */
	     }     /* end for xleft to xright loop */
       }          /* end k loop -                 */
   
   }               /* end for scanline loop*/
   
}



/*
 **********************************************************************
 *                       INTERSECT_SCAN_LINE                          *
 **********************************************************************
 *    Pick out the points a pair(edge) at a time, perspect the points,*
 * and calculate the edges' intersection  with the scan line.         *
 *                                                                    *
 **********************************************************************
*/

intersect_scan_line(num_inter, z_coord, x_coord, y_coord, edge,
		    size_poly, face_ptr)

     long      *num_inter, size_poly;
     double    *z_coord, *x_coord;
     int       y_coord;
     xyz_td   *edge, *face_ptr;

{
      long     pnt, vindex;
      xyz_td  point1, point2;

      *num_inter = 0;
      
      for(pnt = 0; pnt < size_poly; pnt++)
	{ 
	  point1 = face_ptr[pnt];
	  if (pnt == size_poly-1)
	    vindex = 0;
	  else
	    vindex = pnt + 1;
	  point2 = face_ptr[vindex];

   	     /*  see if it intersects this scan line */
	  if ((point1.y >= y_coord && point2.y <= y_coord) ||
	      (point1.y <= y_coord && point2.y >= y_coord)) 
	    {    
	      /* nv1 = v_norm[pnt]; 
		 nv2 = v_norm[vindex]; */
	      calc_intersect(point1,point2,x_coord,y_coord,
			     z_coord, num_inter,edge);
	    }           
	}
    }
                    
ceiling(x)
     double  *x;
{
  int y;
  y = (int)*x;  
  if ((double) y != *x)
    *x = (double) (y + 1);
  else
    *x = (double) y;
}