NAME

       vpRamp - initialize an array with a piecewise-linear ramp

SYNOPSIS

       #include <volpack.h>

       vpResult
       vpRamp(array, stride, num_points, ramp_x, ramp_y)
           float *array;
           int stride;
           int num_points;
           int *ramp_x;
           float *ramp_y;

ARGUMENTS

       array  Output array.

       stride Stride from one array element to the next, in bytes.

       num_points
              Number of entries in the input arrays (ramp_x and ramp_y).

       ramp_x Input array containing indices into array.

       ramp_y Input array containing values to store into array.

DESCRIPTION

       vpRamp  is a utility routine for initializing linear arrays of floating-point numbers with
       piecewise-linear ramps.  A ramp is defined by a set of (x, y) pairs.   The  X  coordinates
       are integers that index entries in the array argument, and the Y coordinates are floating-
       point values to store into the array.  Linearly-interpolated Y values are stored in  array
       elements with indexes in between two of the X values.

       The values in ramp_x most be strictly increasing.  The stride argument may be used to skip
       array elements or to initialize arrays with a non-standard stride.  If the output array is
       a simple linear array of type float then the stride should be sizeof(float).

       This  function  is  useful  for creating lookup tables used for opacity transfer functions
       (see vpSetClassifierTable(3)) and shading functions (see vpSetLookupShader(3)).

ERRORS

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

       VPERROR_BAD_VALUE
              The number of points is less than one or the X values are not strictly increasing.

SEE ALSO

       VolPack(3)