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)