.\" Copyright (c) 1994 The Board of Trustees of The Leland Stanford
.\" Junior University.  All rights reserved.
.\" 
.\" Permission to use, copy, modify and distribute this software and its
.\" documentation for any purpose is hereby granted without fee, provided
.\" that the above copyright notice and this permission notice appear in
.\" all copies of this software and that you do not sell the software.
.\" Commercial licensing is available by contacting the author.
.\" 
.\" THE SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND,
.\" EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
.\" WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
.\" 
.\" Author:
.\"    Phil Lacroute
.\"    Computer Systems Laboratory
.\"    Electrical Engineering Dept.
.\"    Stanford University
.\" 
.\" $Date: 1994/12/31 19:49:53 $
.\" $Revision: 1.1 $
.\"
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.TH vpRamp 3 "" VolPack
.SH NAME
vpRamp \- initialize an array with a piecewise-linear ramp
.SH SYNOPSIS
#include <volpack.h>
.sp
.FS vpResult
\fBvpRamp(\fIarray, stride, num_points, ramp_x, ramp_y\fB)\fR
.FA
float *\fIarray;\fR
.FA
int \fIstride;\fR
.FA
int \fInum_points;\fR
.FA
int *\fIramp_x;\fR
.FA
float *\fIramp_y;\fR
.FE
.SH ARGUMENTS
.IP \fIarray\fR
Output array.
.IP \fIstride\fR
Stride from one array element to the next, in bytes.
.IP \fInum_points\fR
Number of entries in the input arrays (\fIramp_x\fR and \fIramp_y\fR).
.IP \fIramp_x\fR
Input array containing indices into \fIarray\fR.
.IP \fIramp_y\fR
Input array containing values to store into \fIarray\fR.
.SH DESCRIPTION
\fBvpRamp\fR 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 \fIarray\fR 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.
.PP
The values in \fIramp_x\fR most be strictly increasing.  The
\fIstride\fR 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).
.PP
This function is useful for creating lookup tables used for opacity
transfer functions (see vpSetClassifierTable(3)) and shading functions (see
vpSetLookupShader(3)).
.SH ERRORS
The normal return value is VP_OK.  The following error return value
is possible:
.IP VPERROR_BAD_VALUE
The number of points is less than one or the X values are not strictly
increasing.
.SH SEE ALSO
VolPack(3)