NAME

       vpSeti, vpSetd - set the value of an option

SYNOPSIS

       #include <volpack.h>

       vpResult
       vpSeti(vpc, option, value)
           vpContext *vpc;
           int option;
           int value;

       vpResult
       vpSetd(vpc, option, value)
           vpContext *vpc;
           int option;
           double value;

ARGUMENTS

       vpc    VolPack context from vpCreateContext.

       option Constant that specifies the option to be set.

       value  New value for the option.

DESCRIPTION

       These  functions  are  used  to  set  the values of integer- or double-valued options in a
       rendering context.  The following list summarizes the integer-valued options that  can  be
       set with vpSeti:

       VP_CONCAT_MODE
              Choose  whether  transformation  matrices  are premultiplied or postmultiplied.  If
              value  is  VP_CONCAT_LEFT  then  matrices   are   premultiplied.    If   value   is
              VP_CONCAT_RIGHT then matrices are postmultiplied.  Default: VP_CONCAT_RIGHT.

       VP_DEPTH_CUE_SIZE_HINT
              Set  the  suggested  number  of  entries  in  the  depth  cueing lookup table.  See
              vpSetDepthCueing(3).  Default: none

       VP_INT_WIDTH_HINT
              Set the suggested width (in pixels) of the intermediate  image  work  buffer.   See
              vpRenderRawVolume(3).  Default: none

       VP_INT_HEIGHT_HINT
              Set  the  suggested  height (in pixels) of the intermediate image work buffer.  See
              vpRenderRawVolume(3).  Default: none

       VP_SHADOW_LIGHT
              Get the current shadow light (see vpSetShadowLookupShader(3)).   Legal  values  are
              VP_LIGHT0, VP_LIGHT1, ..., VP_LIGHT5.  Default: VP_LIGHT0

       VP_SHADOW_WIDTH_HINT
              Set    the    suggested   width   (in   pixels)   of   the   shadow   buffer   (see
              vpSetShadowLookupShader(3)).  Default: none

       VP_SHADOW_HEIGHT_HINT
              Set   the   suggested   height   (in   pixels)   of   the   shadow   buffer    (see
              vpSetShadowLookupShader(3)).  Default: none

       VP_SHADOW_BIAS
              Set  the  current shadow bias value (see vpSetShadowLookupShader(3)).  The value is
              an integral distance in units of voxels.  Default: 4

       VP_AXIS_OVERRIDE
              Force the rendering routine to composite along a particular principle viewing axis,
              regardless of the current viewing direction.  Legal values are VP_X_AXIS, VP_Y_AXIS
              or VP_Z_AXIS.  Set the value to VP_NO_AXIS to let VolPack choose the  optimal  axis
              automatically (the default).  This option is normally used only for debugging.

       VP_TRACE_SHADOW_K
              When  pixel  tracing  is enabled (see vpTracePixel(3)) and shadows are enabled (the
              VP_SHADOW option to vpEnable(3)), this option is used to choose one  shadow  buffer
              pixel  to  trace.  The value must be a voxel slice number.  The shadow buffer pixel
              that gets traced is the shadow pixel that affects the traced  image  pixel  at  the
              indicated slice.

       The following list summarizes the double-valued options that can be set with vpSetd:

       VP_DEPTH_CUE_QUANTIZATION
              Set the difference in depth between two adjacent entries in the depth cueing lookup
              table (see vpSetDepthCueing(3)).  Must be greater  than  0.0  and  less  than  1.0.
              Default: 1/255

       VP_MAX_RAY_OPACITY
              Set  the  maximum  opacity  threshold.   During  rendering,  when a pixel's opacity
              reaches this threshold no more voxels are composited into the pixel.   To  maximize
              performance,  the  value  should  be as low as possible without adversely affecting
              image quality.  Must be in the range 0.0-1.0 (1.0 is the default and  0.95  is  the
              suggested value).  Default: 1.0

       VP_MIN_VOXEL_OPACITY
              Set  the minimum opacity threshold.  During classification, if a voxel's opacity is
              less than or equal to this threshold then the voxel is discarded before  rendering.
              To  maximize performance, the value should be as high as possible without adversely
              affecting image quality.  Must be in the range 0.0-1.0 (0.0 is the default and 0.05
              is the suggested value).  Default: 0.0

ERRORS

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

       VPERROR_BAD_OPTION
              The option argument is invalid.

       VPERROR_BAD_VALUE
              The value argument is invalid or out of range.

SEE ALSO

       VolPack(3), vpCreateContext(3), vpGeti(3)