Introduction to OpenGL

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Introduction to OpenGL
ECS175 Discussion Session

• Hiroshi Akiba Jan 9, 2004

2
Outline

• What is OpenGL?
• Related Libraries
• Sample Code
• How to compile
• Sample Makefile

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What is OpenGL?

• Low-level graphics library specification
• Provides set of functions to draw small set of
  geometric primitives and to control rendering
  status
• -designed for efficient processing of 3D
  applications
• -hardware independent
• -Language Independent

OpenGL, PHIGS, Direct3D, VRML, Java-3D
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Related Libraries

• OpenGL basic library(GL)
• -device independent graphics functions for
  rendering only
• OpenGL Utility(GLU)
• - simple and complex 3D models
• - Matrix Utilities (gluOrtho2D, gluLookAt,
  gluPerspective)
• OpenGL Utility Toolkit(GLUT)
• - One of the most popular window-system library
• - functions for interacting with any
  screen-windowing system

GLUT
GLUT
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Sample code

• //include ltGL/gl.hgt
• //include ltGL/glu.hgt
• include ltGL/glut.hgt
• void init(void)
• glClearColor(1.0, 1.0, 1.0, 0.0)
• glMatrixMode(GL_PROJECTION)
• gluOrtho2D(0.0, 200.0, 0.0, 150.0)
• void lineSegment(void)
• glClear(GL_COLOR_BUFFER_BIT)
• glColor3f(1.0, 0.0, 0.0)
• glBegin(GL_LINES)
• glVertex2i(180, 15)
• glVertex2i(10, 145)
• glEnd()

int main(int argc, char argv)
glutInit(argc, argv) glutInitDisplayMode(GLUT_
SINGLE GLUT_RGB) glutInitWindowPosition(50,
100) glutInitWindowSize(400, 300)
glutCreateWindow("An Example OpenGL Program")
init() glutDisplayFunc(lineSegment)
glutMainLoop() return 0
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How to compile

• Specify Header files and library location
• EX -I/usr/include
• -L/usr/X11R6/lib
• Specify libraries to use
• EX -lGL -lGLU -lglut -lXmu -lXi

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Sample Makefile
setting build-in variables CXX g SHELLtcsh
necessary to use sed command CXXFLAGS -g
-Wall -I/usr/include library names and
location used when linking LDFLAGS -L/usr/lib
-L/usr/X11R6/lib -lGL -lGLU -lglut -lXmu -lXi
executable filename EXE sample source and
objects filename SRC sampleP80.cpp OBJ
(SRC.cpp.o) (EXE) (OBJ) (CXX)
(CXXFLAGS) (LDFLAGS) (OBJ) -o _at_
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Sample Makefile (Cont)

• clean
• rm (EXE) (OBJ)
• depend
• sed '1,/ gtgtDO NOT DELETE THIS LINEltlt /\!d'
  Makefile gt Makefile.new
• echo ' "make depend" was last run 'date gtgt
  Makefile.new
• (CXX) -MM (CFLAGS) (SRC) gtgt Makefile.new
• mv Makefile Makefile.bak
• mv Makefile.new Makefile
• gtgtDO NOT DELETE THIS LINEltlt
• "make depend" was last run Wed Jan 7
  202214 PST 2004
• sampleP80.o sampleP80.cpp

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References

• 1.Hearn baker, Computer Graphics width OpenGL,
  2004
• 2.Edward Angel, Interactive Computer Graphics A
  Top-Down Approach with OpenGL, 2000
• 3. http//www.opengl.org/