       SippRender [-flags] outputlist xsize ysize [mode] [oversample]
              This  command  does the rendering of a scene to one
              or more image stores.  The  ability  to  render  to
              multiple image stores allows an application to ren-
              der to a Tk photo image and save  the  image  in  a
              file at the same time, for example.

              The  scanning  direction  determines which types of
              image stores  may  be  rendered  together.   Output
              objects  may  be written from top to bottom or from
              bottom to top. File objects are written in only one
              direction or another, while memory resident objects
              can be written in either direction.   Image  stores
              that  are written in opposing directions may not be
              rendered at the same time.  Pixmaps may be used  as
              a  buffer to store images that can then be saved to
              other   image   stores   with   conflicting   scan-
              directions.

              The  image  is  created  with  the pixel dimensions
              xsize by ysize.  outputlist is  a  list  of  output
              target  handles.   The  image  is  written  in  the
              Portable Pixel Map  (PPM)  format  unless  mode  is
              LINE,  in  which case it is written in the Portable
              Bit Map (PBM) format.  fIMode decides in which mode
              the  image  should be rendered and should be one of
              PHONG, GOURAUD, FLAT or LINE.   The  integer  value
              oversampling  controls how much oversampling should
              be done for anti-aliasing. Each pixel will  be  the
              average  of a oversampling X oversampling matrix of
              subpixels.  Oversampling  is  ignored  if  mode  is
              LINE.

              The following optional flags may be specified:

                 o -odd - Render old scanlines, useful for creat-
                 ing interlaced movies.  (Not  allowed  for  LINE
                 mode).

                 o  -even  -  Render even scanlines. (Not allowed
                 for LINE mode).

                 o -both - Render all scan lines.   This  is  the
                 default, only one of -odd, -even or -both may be
                 specified.

                 o -update period - Specified the updated  period
                 when  this  command is used in a Tk application.
                 This is the frequency at which Tk  events,  such
                 as button presses, are handled.  The approximate
                 unit is the time it takes to render  one  pixel.
                 Zero disables updates.  If not specified, period
                 is the size of one scanline.  The processing  of
                 pending   signals   will   also  occur  at  this
                 interval, which may be useful  in  non-Tk  based
                 applications.

                 o  -clear  -  Causes images rendered to Tk photo
                 images to be cleared before rendering the image.
                 This is the default.

                 o  -noclear  -  Causes  images  rendered to a Tk
                 photo image to not be cleared  before  rendering
                 the  image.  The contents of the previously ren-
                 dered image will  remain  until  a  scanline  is
                 overwriten  by the new image.  This is most use-
                 ful for overwriting a LINE rendered  image  with
                 fully  rendered  image.   Only  one of -clear or
                 -noclear may be specified.

                 o -either - Specifies that the image to be  ren-
                 dered  either top down or bottom up.  If no file
                 image store overrides this  specification,  then
                 top-down is used.   This is the default.

                 o  -topdown  -  Causes  the image to be rendered
                 from the top down.  It is useful for  specifying
                 if  scanlines  appear  in  the  a Tk photo image
                 starting at the top.  This may not be  specified
                 with a bottom-up image store.

                 o  -bottomup  -  Causes the image to be rendered
                 from the bottom up.  It is useful for specifying
                 if scanlines appear in a Tk photo image starting
                 at the bottom.  This may not be specified with a
                 bottom-up image store.  Only one of -topdown and
                 -bottomup may be specified.
