bbox2(3G)

NAME
     bbox2, bbox2i, bbox2s - culls and prunes to bounding box and minimum
     pixel radius

FORTRAN 77 SPECIFICATION
     subroutine bbox2(xmin, ymin, x1, y1, x2, y2)
     integer*4 xmin, ymin
     real x1, y1, x2, y2

     subroutine bbox2i(xmin, ymin, x1, y1, x2, y2)
     integer*4 xmin, ymin, x1, y1, x2, y2

     subroutine bbox2s(xmin, ymin, x1, y1, x2, y2)
     integer*4 xmin, ymin
     integer*2 x1, y1, x2, y2

     All of the above routines are functionally the same.  They differ only in
     the declaration types of their parameters.

PARAMETERS
     xmin   expects the width, in pixels, of the smallest displayable feature.

     ymin   expects the height, in pixels, of the smallest displayable
            feature.

     x1     expects the x coordinate of a corner of the bounding box.

     y1     expects the y coordinate of a corner of the bounding box.

     x2     expects the x coordinate of a corner of the bounding box. The
            corner referenced by this parameter must be diagonally opposite
            the corner referenced by the x1 and  y1 parameters.

     y2     expects the y coordinate of a corner of the bounding box. The
            corner referenced by this parameter must be diagonally opposite
            the corner referenced by the x1 and  y1 parameters.

DESCRIPTION
     bbox2 performs the graphical functions known as culling and pruning.
     Culling prevents the system from drawing objects that are less than the
     minimum feature size (xmin and ymin). Pruning prevents the system from
     drawing objects that lie completely outside the viewport.

     To determine whether or not to cull an object, bbox2 tests whether or not
     the display of a rectangle the size of the bounding box is smaller than
     the minimum feature size. To determine whether or not to prune an object,
     bbox2 tests whether or not the bounding box is completely outside the
     viewport.

     Call bbox2 within the definition for an object, just after the call to
     makeob.  If the object must be pruned or culled, the remainder of the
     object definition is ignored.
SEE ALSO
     makeob

NOTES
     This routine does not function in immediate mode.

     This routine is not a free test.  If you use bbox2 too freely, your
     performance can suffer.  Reserve bbox2 for complicated object definitions
     only.