polymo(3G)

NAME
     polymo - control the rendering of polygons

FORTRAN SPECIFICATION
     subroutine polymo(mode)
     integer*4 mode

PARAMETERS
     mode   Expects one of the symbolic constants:

            PYMPOI, draw only points at the vertices.

            PYMLIN, draw lines from vertex to vertex.

            PYMFIL, fill the polygon interior.

            PYMHOL, fill only interior pixels at the boundaries.

DESCRIPTION
     polymo specifies whether polygons are filled, outlined, drawn with points
     at their vertices, or outlined with a hollow fill algorithm.  Affected
     polygons include all polygons that are normally filled, including those
     generated by bgnpol and endpol, by bgntme and endtme, by bgnqst and
     endqst, by arcf, circf, and rectf, and by NURBS surfaces.  Also affected
     are polygons generated by the obsolete pmv, pdr, and pclos commands, and
     by polf and spolf.

     PYMFIL is the default mode.  In this mode polygons are filled with a
     point-sample algorithm.  (Refer to the Graphics Library Programmer's
     Guide for an detailed explanation of point-sampling.)

     PYMPOI causes a single point to be drawn at each polygon vertex,
     including vertices generated by clipping.  All point rendering modes,
     including antialiasing specified by pntsmo, apply to these points.

     PYMLIN causes lines to be drawn from vertex to vertex around the
     perimeter of the polygon.  This line forms a single outline, because it
     passes through both projected vertices and vertices generated by
     clipping.  All line rendering modes, including line width, line stipple
     style, and line antialiasing specified by linesm, apply to these lines.

     PYMHOL supports a special kind of polygon fill with the following
     properties:

     1.   Only pixels on the polygon edge are filled.  These pixels form a
          single-width line (regardless of the current linewi) around the
          inner perimeter of the polygon.

     2.   Only pixels that would have been filled (PYMFIL) are changed (i.e.
          the outline does not extend beyond the exact polygon boundary).
     3.   Pixels that are changed take the exact color and depth values that
          they would have had the polygon been filled.

     Because their pixel depth values are exact, hollow polygons can be
     composed with filled polygons accurately.  Both hidden-line and scribed-
     surface renderings can be done taking advantage of this fact.

SEE ALSO
     bgnpol, endpol, polysm, stenci

NOTES
     XS, XZ, Elan, and Extreme graphics support all polymo options except
     polymo(PYMHOL).  IRIS-4D G, GT, and GTX models, as well as the Personal
     Iris, Iris Entry, Indy, and XL systems do not support polymo.  Use getgde
     to determine whether support for polymo is available.

BUGS
     In order to support polygon fill mode PYMHOL, IRIS-4D VGX and
     RealityEngine models require that the following conditions be met:

     1.   Stencil planes be allocated (at least one plane).

     2.   The stencil planes be initialized to zero prior to drawing hollow
          polygons.

     3.   The stencil planes be used for no other purpose while drawing hollow
          polygons.  (The stencil function is controlled by the hardware and
          must not be user specified.)

     IRIS-4D VGX models have an error in their microcode that results in
     matching errors between pixels generated by PYMFIL and PYMHOL in some
     conditions.  This error will be corrected in the next software release.

     PYMHOL is not supported on Impact or Infinite Reality.