#define XMIN 0.0
#define XMAX 639
#define YMIN 0.0
#define YMAX 479

#define ZMIN 0.25     /* these values assume normalised */ 
#define ZMAX 1.0      /* z coordinates of the line      */

#define EPSILON 1e-6

#define Zero(a) ((a)<EPSILON && (a)>-EPSILON)

typedef struct {
  float x, y, z;
} Point;