       SippRender [-flags] outputlist xsize ysize [mode] [oversample]
              This  command  does the rendering of a scene to one
              or more Image Storage Object (ISO).  The ISOs  that
              are  currently  supported  are  PBMPlus PPM and PBM
              files, Utah Raster Tool Kit RLE files, pixmaps  and
              the Tk photo widget.  All output objects may not be
              available, depending on how Tcl-SIPP  will  linked.
              The  ability  to  render to multiple ISOs allows an
              application to render to the Photo widget  an  save
              the image in a file at the same time, for example

              The attribute that controls which types of ISOs may
              be rendered together is  the  scanning  directions.
              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 resi-
              dent objects can be written  in  either  direction.
              ISOs  that  are  written in opposing directions may
              not be rendered at the same time.   RLE  files  are
              written from bottom to top, PBMPlus files are writ-
              ten from top to bottom and  the  photo  widget  and
              pixmaps   may   be  written  in  either  direction.
              Pixmaps may be used as a  buffer  to  store  images
              that  can  then  be  saved to ISOs 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  inter-
                 val,  which may be useful in non-Tk based appli-
                 cations.

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

                 o -noclear - Causes images rendered to the photo
                 widget  to  not  be cleared before rendering the
                 image.  The contents of the previously  rendered
                 image will remain until a scanline is overwriten
                 by the new image.  This is most useful for over-
                 writing  a  LINE  rendered image with fully ren-
                 dered 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
                 ISO  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 photo widget starting
                 at  the  top.   This may not be specified with a
                 bottom-up ISO.

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