#
# (c) Copyright 1993, Silicon Graphics, Inc.
# ALL RIGHTS RESERVED 
# Permission to use, copy, modify, and distribute this software for 
# any purpose and without fee is hereby granted, provided that the above
# copyright notice appear in all copies and that both the copyright notice
# and this permission notice appear in supporting documentation, and that 
# the name of Silicon Graphics, Inc. not be used in advertising
# or publicity pertaining to distribution of the software without specific,
# written prior permission. 
#
# THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "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.  IN NO EVENT SHALL SILICON
# GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
# SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
# KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
# LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
# THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
# ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
# ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
# POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
# 
# US Government Users Restricted Rights 
# Use, duplication, or disclosure by the Government is subject to
# restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
# (c)(1)(ii) of the Rights in Technical Data and Computer Software
# clause at DFARS 252.227-7013 and/or in similar or successor
# clauses in the FAR or the DOD or NASA FAR Supplement.
# Unpublished-- rights reserved under the copyright laws of the
# United States.  Contractor/manufacturer is Silicon Graphics,
# Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
#
# OpenGL(TM) is a trademark of Silicon Graphics, Inc.
#/
#
#  alpha3D.c
#  This program demonstrates how to intermix opaque and
#  alpha blended polygons in the same scene, by using glDepthMask.
#  Pressing the left mouse button toggles the eye position.
#/

use opengl;
package opengl;

sub myinit {
    my $mat_ambient = newfv4(0.0,0.0,0.0,0.15);
    my $mat_specular = newfv4(1.0, 1.0, 1.0, 0.15 );
    my $mat_shininess = newfv4(15.0,0,0,0);
    glMaterialfv($GL_FRONT, $GL_AMBIENT, $mat_ambient);
    glMaterialfv($GL_FRONT, $GL_SPECULAR, $mat_specular);
    glMaterialfv($GL_FRONT, $GL_SHININESS, $mat_shininess);
    glEnable ($GL_LIGHTING);
    glEnable ($GL_LIGHT0);
    glDepthFunc($GL_LESS);
    glEnable($GL_DEPTH_TEST);
}

$eyePosition = $GL_FALSE;

sub toggleEye {
     if ($eyePosition == 1) {
        $eyePosition = $GL_FALSE;
    } else {
	$eyePosition = $GL_TRUE;
    }
 }

sub display {
    my $position = newfv4( 0.0, 0.0, 1.0, 1.0 );
    my $mat_torus = newfv4( 0.75, 0.75, 0.0, 1.0 );
    my $mat_cylinder = newfv4( 0.0, 0.75, 0.75, 0.15 );
    glClear ($GL_COLOR_BUFFER_BIT | $GL_DEPTH_BUFFER_BIT);
    glLightfv ($GL_LIGHT0, $GL_POSITION, $position);
    glPushMatrix ();
    if ($eyePosition == 1) {
	gluLookAt (0.0, 0.0, 9.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0); 
    } else {
	gluLookAt (0.0, 0.0, -9.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0); 
    }
     glPushMatrix ();
     glTranslatef (0.0, 0.0, 1.0);    
     glMaterialfv($GL_FRONT, $GL_DIFFUSE, $mat_torus);
     auxSolidTorus (0.275, 0.85);
     glPopMatrix ();
     glEnable ($GL_BLEND);
     glDepthMask ($GL_FALSE);
     glBlendFunc ($GL_SRC_ALPHA, $GL_ONE);
     glMaterialfv($GL_FRONT, $GL_DIFFUSE, $mat_cylinder);
     glTranslatef (0.0, 0.0, -1.0);    
     auxSolidCylinder (1.0, 2.0);
     glDepthMask ($GL_TRUE);
     glDisable ($GL_BLEND);
     glPopMatrix ();
     glFlush ();
}

sub Reshape {
    my ($w,$h) = @_;
    glViewport(0, 0, $w, $h);
    glMatrixMode($GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(30.0, 1.0*$w/$h, 1.0, 20.0);
    glMatrixMode($GL_MODELVIEW);
    glLoadIdentity();
}

auxInitDisplayMode ($AUX_SINGLE | $AUX_RGB | $AUX_DEPTH);
auxInitPosition (0, 0, 500, 500);
auxInitWindow ("alpha3D");
myinit();
Reshape(500,500);
display();
sleep(10);