#
# Copyright (c) 1993-1997, 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
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# or publicity pertaining to distribution of the software without specific,
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#
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# AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
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# GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
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# LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
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# ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
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# 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# Unpublished-- rights reserved under the copyright laws of the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(R) is a registered trademark of Silicon Graphics, Inc.
#
# bezcurve.c			
# This program uses evaluators to draw a Bezier curve.

require "opengl"
include Gl,Glu,Glut

$ctrlpoints = [
	[-4.0,-4.0, 0.0],
	[-2.0, 4.0, 0.0], 
	[ 2.0,-4.0, 0.0],
	[ 4.0, 4.0, 0.0]
	]

def init
	glClearColor(0.0, 0.0, 0.0, 0.0)
	glShadeModel(GL_FLAT)
	glMap1d(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, 4, $ctrlpoints.flatten)
	glEnable(GL_MAP1_VERTEX_3)
end

display = proc do
	glClear(GL_COLOR_BUFFER_BIT)
	glColor(1.0, 1.0, 1.0)
	glBegin(GL_LINE_STRIP)
	for i in 0..30
		glEvalCoord1d(i.to_f/30.0)
	end
	glEnd()
	# The following code displays the control points as dots. 
	glPointSize(5.0)
	glColor(1.0, 1.0, 0.0)
	glBegin(GL_POINTS)
	for i in 0...4
		glVertex($ctrlpoints[i])
	end
	glEnd()
	glutSwapBuffers()
end

reshape = proc do |w, h|
	glViewport(0, 0, w, h)
	glMatrixMode(GL_PROJECTION)
	glLoadIdentity()
	if (w <= h)
		glOrtho(-5.0, 5.0, -5.0*h/w, 5.0*h/w, -5.0, 5.0)
	else
		glOrtho(-5.0*w/h, 5.0*w/h, -5.0, 5.0, -5.0, 5.0)
	end
	glMatrixMode(GL_MODELVIEW)
	glLoadIdentity()
end

keyboard = proc do |key, x, y|
	case (key)
	when ?\e
		exit(0)
	end
end

glutInit()
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB)
glutInitWindowSize(500, 500)
glutInitWindowPosition(100, 100)
glutCreateWindow()
init()
glutDisplayFunc(display)
glutReshapeFunc(reshape)
glutKeyboardFunc(keyboard)
glutMainLoop()