pntsmo(3G)

NAME
     pntsmo - specify antialiasing of points

FORTRAN 77 SPECIFICATION
     subroutine pntsmo(mode)
     integer*4 mode

PARAMETERS
     mode   expects one of two values:

            SMPOFF defeats antialiasing of points (default).

            SMPON enables antialiasing of points.  It can be modified by an
            optional symbolic constant:

            SMPSMO indicates that a higher quality filter should be used
            during point drawing.  This filter typically requires that more
            pixels be modified, and therefore potentially reduces the rate at
            which antialiased points are rendered.

     The constant SMPSMO is specified by bitwise ORing it, or by adding it, to
     SMPON.  For example:

          pntsmo(SMPON + SMPSMO)


     enables antialiased point drawing with the highest quality, and
     potentially lowest performance, algorithm.  The modifier is a hint, not a
     directive, and is therefore ignored by systems that do not support the
     requested feature.

DESCRIPTION
     pntsmo controls the capability to draw antialiased points.  You can draw
     antialiased points in either color map mode or RGB mode.

     For color map antialiased points to draw correctly, you must initialize a
     16-entry colormap block (whose lowest entry location is a multiple of 16)
     to a ramp between the background color (lowest index) and the point color
     (highest index).  Before drawing points, clear the area to the background
     color.

     The pntsmooth hardware replaces the least significant 4 bits of the
     current color index with bits that represent pixel coverage.  Therefore,
     by changing the current color index (only the upper 8 bits are
     significant) you can select among many 16-entry color ramps, representing
     different colors and intensities.  You can draw depthcued antialiased
     points in this manner.

     The z-buffer hardware can be used to improve the quality of color map
     antialiased point images.  Enabled in the standard depth-comparison mode,
     it ensures that points nearer the viewer obscure more distant points.
     Alternately, the z-buffer hardware can be used to compare color values by
     issuing:

              zbuffe(.TRUE.)
               zsourc(ZSRCCO)
               zfunct(ZFGREA)


     Pixels are then replaced only by 'brighter' values, resulting in better
     intersections between points drawn using the same ramp.

     RGB antialiased points can be drawn only on machines that support
     blending.  For these points to draw correctly, the blendfunction must be
     set to merge new pixel color components into the framebuffer using the
     incoming (source) alpha values.  Incoming color components should always
     be multiplied by the source alpha (BFSA).  Current (destination) color
     components can be multiplied either by one minus the source alpha
     (BFMSA), resulting in a weighted average blend, or by one (BFONE),
     resulting in color accumulation to saturation; issue:

          c    weighted average
               blendf(BFSA, BFMSA)


     or

          c    saturation
               blendf(BFSA, BFONE)


     The pntsmooth hardware scales incoming alpha components by an 8-bit
     computed coverage value.  Therefore reducing the incoming source alpha
     results in transparent, antialiased points.

     RGB antialiased points draw correctly over any background image.  It is
     not necessary to clear the area in which they are to be drawn.

     Both color map and RGB mode points are antialiased effectively only when
     subpixel mode is enabled; issue:

               subpix(.TRUE.)


     The size of antialiased points is controlled by pntsiz and pntszf.
     Although point size can be arbitrarily specified, only a small, hardware
     specific number of point sizes is actually supported.  (Refer to the
     pntsiz manpage.)

     The modifier SMPSMO can be ORed or ADDed to the symbolic constant SMPON
     when antialiased points are enabled.  When this is done, a higher quality
     and potentially lower performance filter is used to scan convert
     antialiased points.  SMPSMO is a hint, not a directive.  Thus a higher
     quality filter is used only if it is available.
SEE ALSO
     bgnpoi, blendf, endpoi, gversi, pntsiz, linesm, subpix, v, zbuffe,
     zfunct, zsourc

NOTES
     This routine does not function on IRIS-4D B or G models, or on the
     Personal Iris.  Use gversi to determine which type you have.

     IRIS-4D GT and GTX models, as well as the Personal Iris, Iris Entry,
     Indy, XL, XS, XS24, XZ, Elan and Extreme systems do not support SMPSMO.
     These systems ignore this hint.

     Iris Entry pntsmo support is only valid for color index mode.

BUGS
     Color-comparison z-buffering is not supported on the IRIS-4D GT or GTX
     models.