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vpGetTimer(3)		    Library Functions Manual		   vpGetTimer(3)

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 li-
     brary.  To use them, the library must be compiled with a special flag:  ei-
     ther  -DHAVE_LORES_TIMER  (for  machine that support the gettimeofday C li-
     brary call) or -DHAVE_HIRES_TIMER (for SGI machines that support high-reso-
     lution  memory-mapped  I/O  timers;   on	a   Challenge	or   ONYX,   the
     -DHAVE_64BIT_TIMER must also be specified).  If one of these flags is spec-
     ified  at compile time then VolPack maintains a table recording the accumu-
     lated 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_OC-
	    TREE, VPTIMER_COMPOSITE, VPTIMER_DEPTHCUE, and VPTIMER_WARP).

     VPTIMER_COMPOSITE
	    Time the routine that computes the intermediate image from the  vol-
	    ume  (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  inter-
	    mediate 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 pos-
     sible:

     VPERROR_BAD_OPTION
	    The option argument is invalid.

SEE ALSO
     VolPack(3), vpCreateContext(3)

VolPack 							   vpGetTimer(3)

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