/* up_vec.c 1.1 */
/*
    Copyright 1992, 1993 O'Reilly and Associates, Inc.  Permission to
    use, copy, and modify this program is hereby granted, as long as
    this copyright notice appears in each copy of the program source
    code.
*/

#include <X11/PEX5/PEXlib.h>
#include <math.h>

void
compute_up_vec_transform( up_vec, xform )
    PEXVector2D		*up_vec;
    PEXMatrix3x3	xform;
{
    double	angle;

    angle = atan2( up_vec->y, up_vec->x );
    PEXRotate2D( angle, xform );
}