#
# Copyright (c) 1993-1997, Silicon Graphics, Inc.
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# 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
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# Unpublished-- rights reserved under the copyright laws of the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(R) is a registered trademark of Silicon Graphics, Inc.
#
# aapoly.c
# This program draws filled polygons with antialiased
# edges.  The special GL_SRC_ALPHA_SATURATE blending 
# function is used.
# Pressing the 't' key turns the antialiasing on and off.
require 'opengl'
include Gl,Glu,Glut

$polySmooth = true

def init
	glCullFace(GL_BACK)
	glEnable(GL_CULL_FACE)
	glBlendFunc(GL_SRC_ALPHA_SATURATE, GL_ONE)
	glClearColor(0.0, 0.0, 0.0, 0.0)
end

NFACE=6
NVERT=8
$indices = [
	[4, 5, 6, 7], [2, 3, 7, 6], [0, 4, 7, 3],
	[0, 1, 5, 4], [1, 5, 6, 2], [0, 3, 2, 1]
]

def drawCube(x0, x1, y0, y1, z0, z1)
	v = [[],[],[],[],[],[],[],[]]
	c = [
		[0.0, 0.0, 0.0, 1.0], [1.0, 0.0, 0.0, 1.0],
		[0.0, 1.0, 0.0, 1.0], [1.0, 1.0, 0.0, 1.0],
		[0.0, 0.0, 1.0, 1.0], [1.0, 0.0, 1.0, 1.0],
		[0.0, 1.0, 1.0, 1.0], [1.0, 1.0, 1.0, 1.0]
	]
	
	# indices of front, top, left, bottom, right, back faces
	
	v[0][0] = v[3][0] = v[4][0] = v[7][0] = x0
	v[1][0] = v[2][0] = v[5][0] = v[6][0] = x1
	v[0][1] = v[1][1] = v[4][1] = v[5][1] = y0
	v[2][1] = v[3][1] = v[6][1] = v[7][1] = y1
	v[0][2] = v[1][2] = v[2][2] = v[3][2] = z0
	v[4][2] = v[5][2] = v[6][2] = v[7][2] = z1
	
	glEnableClientState(GL_VERTEX_ARRAY)
	glEnableClientState(GL_COLOR_ARRAY)
	glVertexPointer(3, GL_FLOAT, 0, v.flatten!.pack("f*"))
	glColorPointer(4, GL_FLOAT, 0, c.flatten!.pack("f*"))
	glDrawElements(GL_QUADS, NFACE*4, GL_UNSIGNED_BYTE, $indices.flatten.pack("C*"))
	glDisableClientState(GL_VERTEX_ARRAY)
	glDisableClientState(GL_COLOR_ARRAY)
end

# Note:  polygons must be drawn from front to back
# for proper blending.
display = proc do
	if ($polySmooth)
		glClear(GL_COLOR_BUFFER_BIT)
		glEnable(GL_BLEND)
		glEnable(GL_POLYGON_SMOOTH)
		glDisable(GL_DEPTH_TEST)
	else
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
		glDisable(GL_BLEND)
		glDisable(GL_POLYGON_SMOOTH)
		glEnable(GL_DEPTH_TEST)
	end
	
	glPushMatrix()
	glTranslate(0.0, 0.0, -8.0)    
	glRotate(30.0, 1.0, 0.0, 0.0)
	glRotate(60.0, 0.0, 1.0, 0.0) 
	drawCube(-0.5, 0.5, -0.5, 0.5, -0.5, 0.5)
	glPopMatrix()
	glutSwapBuffers()
end

reshape = proc do |w, h|
	glViewport(0, 0, w, h)
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	gluPerspective(30.0,  w.to_f/ h.to_f, 1.0, 20.0)
	glMatrixMode(GL_MODELVIEW)
	glLoadIdentity()
end

keyboard = proc do |key, x, y|
	case (key)
		when ?t ,?T
			$polySmooth = !$polySmooth
			glutPostRedisplay()
		when ?\e
			exit(0)  # Escape key
	end
end

# Main Loop
glutInit
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_ALPHA | GLUT_DEPTH)
glutInitWindowSize(500, 500)
glutInitWindowPosition(100, 100)
glutCreateWindow($0)
init()
glutReshapeFunc(reshape)
glutKeyboardFunc(keyboard)
glutDisplayFunc(display)
glutMainLoop()