No, but it is a simpler, if not quite as well explained,
matrix generator than the PEX code.
/* glu.c */
* Copyright (C) 1995 Brian Paul (brianp@ssec.wisc.edu)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
void gluLookAt( GLdouble eyex, GLdouble eyey, GLdouble eyez,
GLdouble centerx, GLdouble centery, GLdouble centerz,
GLdouble upx, GLdouble upy, GLdouble upz )
{
GLdouble m[16];
GLdouble x[3], y[3], z[3];
GLdouble mag;
/* Make rotation matrix */
/* Z vector */
z[0] = eyex - centerx;
z[1] = eyey - centery;
z[2] = eyez - centerz;
mag = sqrt( z[0]*z[0] + z[1]*z[1] + z[2]*z[2] );
if (mag) { /* mpichler, 19950515 */
z[0] /= mag;
z[1] /= mag;
z[2] /= mag;
}
/* Y vector */
y[0] = upx;
y[1] = upy;
y[2] = upz;
/* X vector = Y cross Z */
x[0] = y[1]*z[2] - y[2]*z[1];
x[1] = -y[0]*z[2] + y[2]*z[0];
x[2] = y[0]*z[1] - y[1]*z[0];
/* Recompute Y = Z cross X */
y[0] = z[1]*x[2] - z[2]*x[1];
y[1] = -z[0]*x[2] + z[2]*x[0];
y[2] = z[0]*x[1] - z[1]*x[0];
/* mpichler, 19950515 */
/* cross product gives area of parallelogram, which is < 1.0 for
* non-perpendicular unit-length vectors; so normalize x, y here
*/
mag = sqrt( x[0]*x[0] + x[1]*x[1] + x[2]*x[2] );
if (mag) {
x[0] /= mag;
x[1] /= mag;
x[2] /= mag;
}
mag = sqrt( y[0]*y[0] + y[1]*y[1] + y[2]*y[2] );
if (mag) {
y[0] /= mag;
y[1] /= mag;
y[2] /= mag;
}
#define M(row,col) m[col*4+row]
M(0,0) = x[0]; M(0,1) = x[1]; M(0,2) = x[2]; M(0,3) = 0.0;
M(1,0) = y[0]; M(1,1) = y[1]; M(1,2) = y[2]; M(1,3) = 0.0;
M(2,0) = z[0]; M(2,1) = z[1]; M(2,2) = z[2]; M(2,3) = 0.0;
M(3,0) = 0.0; M(3,1) = 0.0; M(3,2) = 0.0; M(3,3) = 1.0;
#undef M
glMultMatrixd( m );
/* Translate Eye to Origin */
glTranslated( -eyex, -eyey, -eyez );
}