NAME

       vpGetTimer, vpClearTimer - interval timer facility

SYNOPSIS

       #include <volpack.h>

       vpResult
       vpGetTimer(vpc, option, iptr)
           vpContext *vpc;
           int option;
           int *iptr;;

       vpResult
       vpClearTimer(vpc, option)
           vpContext *vpc;
           int option;

ARGUMENTS

       vpc    VolPack context from vpCreateContext.

       option Constant that specifies a particular timer.

       iptr   Location for storing the timer value.

DESCRIPTION

       These  functions  are  used  for measuring the performance of the VolPack library.  To use
       them, the library must be compiled with a special  flag:  either  -DHAVE_LORES_TIMER  (for
       machine  that  support  the  gettimeofday  C  library call) or -DHAVE_HIRES_TIMER (for SGI
       machines that support high-resolution memory-mapped I/O timers; on a  Challenge  or  ONYX,
       the  -DHAVE_64BIT_TIMER  must  also  be specified).  If one of these flags is specified at
       compile time then VolPack maintains a  table  recording  the  accumulated  time  spent  in
       various  operations.   Note  that  some  of  the operations can only be timed with a high-
       resolution timer; time values will not be recorded and will appear to be  zero  if  a  low
       resolution timer is specified at compile time.

       vpGetTimer retrieves the accumulated time for a particular operation.  The option argument
       specifies which operation:

       VPTIMER_SHADE
              Time the routine that computes the contents of the shading lookup table.

       VPTIMER_RENDER
              Time  the  routine  that   renders   a   volume   (includes   VPTIMER_CLSFY_OCTREE,
              VPTIMER_COMPOSITE, VPTIMER_DEPTHCUE, and VPTIMER_WARP).

       VPTIMER_COMPOSITE
              Time  the  routine  that  computes the intermediate image from the volume (includes
              VPTIMER_CLEAR,  VPTIMER_TRAVERSE_OCTREE,  VPTIMER_ERT,  VPTIMER_TRAVERSE_RUNS,  and
              VPTIMER_PROCESS_VOXELS).

       VPTIMER_DEPTHCUE
              Time the routine that performs the depth cueing fixup on the intermediate image.

       VPTIMER_WARP
              Time the routine that warps the intermediate image into the final image.

       VPTIMER_TRAVERSE_RUNS
              Time  the  portion of the compositing routine devoted to traversing the volume data
              structures.

       VPTIMER_PROCESS_VOXELS
              Time the portion of the compositing routine devoted to compositing voxels into  the
              intermediate image.

       VPTIMER_ERT
              Time the early-ray termination checks during compositing.

       VPTIMER_CLSFY_OCTREE
              Time the octree classification stage.

       VPTIMER_TRAVERSE_OCTREE
              Time the portion of the compositing routine devoted to traversing the octree.

       VPTIMER_CLEAR
              Time   the  routine  that  clears  the  intermediate  image  at  the  beginning  of
              compositing.

       The routine stores the accumulated time since the last call to vpClearTimer (or since  the
       beginning  of  the program) in the location specified by iptr.  The units of the value are
       microseconds.

       vpClearTimer sets the specified timer value back to zero.

ERRORS

       The normal return value is VP_OK.  The following error return value is possible:

       VPERROR_BAD_OPTION
              The option argument is invalid.

SEE ALSO

       VolPack(3), vpCreateContext(3)