#
# Copyright (c) Mark J. Kilgard, 1994.
#
# (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# Unpublished-- rights reserved under the copyright laws of the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.
#
# stencil.c
# This program draws two rotated tori in a window.  
# A diamond in the center of the window masks out part 
# of the scene.  Within this mask, a different model 
# (a sphere) is drawn in a different color.
#
require 'opengl'
require 'rational'
include Gl,Glu,Glut

YELLOWMAT=1
BLUEMAT=2

def myinit
	yellow_diffuse = [ 0.7, 0.7, 0.0, 1.0 ]
	yellow_specular = [ 1.0, 1.0, 1.0, 1.0 ]
	
	blue_diffuse = [ 0.1, 0.1, 0.7, 1.0 ]
	blue_specular = [ 0.1, 1.0, 1.0, 1.0 ]
	
	position_one = [ 1.0, 1.0, 1.0, 0.0 ]
	
	glNewList(YELLOWMAT, GL_COMPILE)
	glMaterial(GL_FRONT, GL_DIFFUSE, yellow_diffuse)
	glMaterial(GL_FRONT, GL_SPECULAR, yellow_specular)
	glMaterial(GL_FRONT, GL_SHININESS, 64.0)
	glEndList()
	
	glNewList(BLUEMAT, GL_COMPILE)
	glMaterial(GL_FRONT, GL_DIFFUSE, blue_diffuse)
	glMaterial(GL_FRONT, GL_SPECULAR, blue_specular)
	glMaterial(GL_FRONT, GL_SHININESS, 45.0)
	glEndList()
	
	glLight(GL_LIGHT0, GL_POSITION, position_one)
	
	glEnable(GL_LIGHT0)
	glEnable(GL_LIGHTING)
	glEnable(GL_DEPTH_TEST)
	
	glClearStencil(0x0)
	glEnable(GL_STENCIL_TEST)
end

#  Draw a sphere in a diamond-shaped section in the
#  middle of a window with 2 tori.
display = Proc.new do
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
	
	# draw blue sphere where the stencil is 1
	glStencilFunc(GL_EQUAL, 0x1, 0x1)
	glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP)
	glCallList(BLUEMAT)
	glutSolidSphere(0.5, 15, 15)
	
	# draw the tori where the stencil is not 1
	glStencilFunc(GL_NOTEQUAL, 0x1, 0x1)
	glPushMatrix()
	glRotate(45.0, 0.0, 0.0, 1.0)
	glRotate(45.0, 0.0, 1.0, 0.0)
	glCallList(YELLOWMAT)
	glutSolidTorus(0.275, 0.85, 15, 15)
	glPushMatrix()
	glRotate(90.0, 1.0, 0.0, 0.0)
	glutSolidTorus(0.275, 0.85, 15, 15)
	glPopMatrix()
	glPopMatrix()

	glutSwapBuffers()
end

#  Whenever the window is reshaped, redefine the 
#  coordinate system and redraw the stencil area.
myReshape = Proc.new do |w, h|
	glViewport(0, 0, w, h)
	
	# create a diamond shaped stencil area
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	if w<=h
		gluOrtho2D(-3.0, 3.0, -3.0*h/w, 3*h/w)
	else
		gluOrtho2D(-3.0*w/h, 3.0*w/h, -3.0, 3)
	end
	glMatrixMode(GL_MODELVIEW)
	glLoadIdentity()
	
	glClear(GL_STENCIL_BUFFER_BIT)
	glStencilFunc(GL_ALWAYS, 0x1, 0x1)
	glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE)
	glBegin(GL_QUADS)
	glVertex2f(-1.0, 0.0)
	glVertex2f(0.0, 1.0)
	glVertex2f(1.0, 0.0)
	glVertex2f(0.0, -1.0)
	glEnd()
	
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	GLU.Perspective(45.0,  w.to_f/h.to_f, 3.0, 7.0)
	glMatrixMode(GL_MODELVIEW)
	glLoadIdentity()
	glTranslate(0.0, 0.0, -5.0)
end

keyboard = Proc.new do |key, x, y|
	case (key)
		when ?\e
		exit(0);
	end
end

#  Main Loop
#  Open window with initial window size, title bar, 
#  RGB display mode, and handle input events.
glutInit()
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL)
glutInitWindowSize(500, 500)
glutInitWindowPosition(100, 100)
glutCreateWindow($0)
myinit
glutReshapeFunc(myReshape)
glutDisplayFunc(display)
glutKeyboardFunc(keyboard)
glutMainLoop()