OpenGL Review

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OpenGL Review
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What is OpenGL?

• OpenGL (Open Graphics Library) is a standard
  specification defining a cross-language
  cross-platform API for writing applications that
  produce 2D and 3D computer graphics. from
  Wikipedia
• State machine
• For example, set the color, all subsequent
  drawing will be in this color until you change
  the color.

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Other libraries

• The OpenGL Utility Library (GLU)
• Routines that accomplishes some tasks by calling
  low-level OpenGL commands
• Provided as part of OpenGL implementation
• Prefix glu
• The OpenGL Utility Toolkit (GLUT)
• window system-independent toolkit
• Prefix glut

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Reference materials

• The Red book
• http//www.glprogramming.com/red/
• The website
• http//www.opengl.org/

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Setup the environment in Visual Studio

• http//csf11.acs.uwosh.edu/cs371/visualstudio/

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Includes

• include ltGL/glut.hgt
• Put it before stdlib.h

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GLUTWindow management

• glutInit(int argc, char argv) initializes.
  glutInit() should be called before any other GLUT
  routine.
• glutInitDisplayMode(unsigned int mode) specifies
  whether to use an RGBA or color-index color
  model. For example, a window with double
  buffering, the RGBA color model, and a depth
  buffer glutInitDisplayMode(GLUT_DOUBLE
  GLUT_RGB GLUT_DEPTH).
• glutInitWindowPosition(int x, int y) specifies
  the screen location for the upper-left corner of
  your window.
• glutInitWindowSize(int width, int size) specifies
  the size, in pixels, of your window.
• int glutCreateWindow(char string) creates a
  window with an OpenGL context.

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The display callback

• glutDisplayFunc(void (func)(void)) .Whenever
  GLUT determines the contents of the window need
  to be redisplayed, the callback function
  registered by glutDisplayFunc() is executed.
  Therefore, you should put all the routines you
  need to redraw the scene in the display callback
  function.
• If your program changes the contents of the
  window, sometimes you will have to call
  glutPostRedisplay(void), which gives
  glutMainLoop() a nudge to call the registered
  display callback at its next opportunity.

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Hello world demo

• glutMainLoop() is the last to be called, and it
  is never exited once entered.
• Things that only need to be done once should be
  called only once in init().
• More on GLUT
• http//www.glprogramming.com/red/appendixd.html

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User input

• Mouse input
• Button clicking
• void glutMouseFunc(void (func)(int button, int
  state, int x, int y))
• Motion
• glutMotionFunc( void (func)(int x, int y))
• Keyboard input
• Key pressing
• void glutKeyboardFunc(void (func)(unsigned char
  key, int x, int y))
• Window resizing
• void glutReshapeFunc(void (func)(int w, int h))

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Quick Demo
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Tranformation

• Rotate
• void glRotatef(GLfloat angle, GLfloat x, GLfloat
  y, GLfloat z)
• Translate
• void glTranslatef (GLfloat x, GLfloat y, GLfloat
  z)
• Scale
• void glScalef(GLfloat x, GLfloat y, GLfloat z)

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Snowman demo
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Homework 1

• Backface Culling
• void glCullFace(GLenum mode)
• glEnable(GL_CULL_FACE)
• Cull faces that are facing back based on vertex
  normals
• View frustum culling
• http//www.lighthouse3d.com/opengl/viewfrustum/
• Big models (PLY)

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Homework 1

• User input
• Backface culling
• View-frustum culling