Chap 2 Write a Simple OpenGL Program

1
Chap 2 Write a Simple OpenGL Program
2
Preparing 1/2

• environmentMicrosoft Visual C 6.0?Microsoft
  Visual C .Net
• Also needGLUT
• http//www.xmission.com/nate/glut.html

3
Preparing 2/2

• On Microsoft Visual C 6.0
• Put glut.h into ltMSVCgt/include/GL/
• Put glut.lib into ltMSVCgt/lib/
• Put glut32.dll into ltwindowgt/System32/
• On Microsoft Visual C .Net
• Put glut.h into ltMSVCgt/platformSDK/include/GL/
• Put glut.lib into ltMSVCgt/platformSDK/lib/
• Put glut32.dll into ltwindowgt/System32/

4
Books

• OpenGL Programming Guide (Red-book)
• OpenGL Reference Manual (Blue-book)
• OpenGL SuperBible

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OpenGL Utility Toolkit (GLUT)

• A window system-independent toolkit to hide the
  complexity of differing window system APIs.
• Providing following operations
• Initializing and creating window
• Handling window and input events
• Drawing basic 3D objects
• Running the program
• Use the prefix of glut (ex glutCreateWindow)

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Write an OpenGL Program 1/7

• Microsoft Visual C 6.0
• Step 1 create a Win32 Console Application project

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Write an OpenGL Program 2/7

• Step 2Press Alt-F7,brings Project
  Settings,select Link

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Write an OpenGL Program 3/7

• Step 3add opengl32.lib glu32.lib glut32.lib
  into Object/library modules
• Step 4write your code
• Step 5compile

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Write an OpenGL Program 4/7

• Microsoft Visual C .Net
• Step 1create Win32 console project

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Write an OpenGL Program 5/7

• Step 2 check empty project

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Write an OpenGL Program 6/7

• Step 3select project / property / linker /
  input
• Step 4 add opengl32.lib glu32.lib glut32.lib

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Write an OpenGL Program 7/7

• Step 5 add a new C source file
• Step 6write your code
• Step 7compile

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A simple OpenGL program 1/2

• includeltGL/glut.hgt
• void GL_display()
• glClearColor(0.0f, 0.0f, 0.0f, 0.0f)
• glClear(GL_COLOR_BUFFER_BIT)
• glColor3f(1.0f, 1.0f, 1.0f)
• glutSolidCube(1.0)
• glFlush()
• void GL_reshape(GLsizei w, GLsizei h)
• glViewport(0, 0, w, h)
• glMatrixMode(GL_PROJECTION)
• glLoadIdentity()
• glOrtho(-2.0f, 2.0f, -2.0f, 2.0f, -2.0f, 2.0f)
• glMatrixMode(GL_MODELVIEW)
• glLoadIdentity()

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A simple OpenGL program 2/2

• void main(int argc, char argv)
• glutInit(argc, argv)
• glutInitDisplayMode(GLUT_SINGLE GLUT_RGB)
• glutCreateWindow("sample")
• glutDisplayFunc(GL_display)
• glutReshapeFunc(GL_reshape)
• glutMainLoop()

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OpenGL command Syntax 1/2

• OpenGL commands use the prefix gl and initial
  capital letters for each word ex glClearColor
• OpenGL defined constants begin with GL_ , use all
  capital letters and underscores to separate words
  ex GL_COLOR_BUFFER_BIT

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OpenGL command Syntax 2/2
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State management 1/2

• OpenGL is a state machine
• You put it into various states (or modes) that
  then remain in effect until you change them.
• Each state variable or mode has a default value,
  and at any point can query the system for each
  variables current value.

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State management 2/2

• glEnable(GLenum), glDisable(GLenum)
• Enable and disable some state.
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc01_3l5x.asp
• glIsEnable(GLenum)
• Query if the specific state is enabled.
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc03_7pgk.asp
• glGetBooleanv(), glGetIntegerv(), glGetFloatv(),
  glGetDoublev(), glGetPointerv()
• Query the specific state value
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc02_5ub8.asp

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Program detail 1/5

• Initializing and creating a window
• void glutInit(int , char)
• Initializing the GLUT library.
• Should be called before any other GLUT routine.
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node10.html
• void glutInitDisplayMode(unsigned int)
• Specify a display mode for windows created.
• GLUT_RGB / GLUT_RGBA / GLUT_INDEX
• GLUT_SINGLE / GLUT_DOUBLE
• GLUT_DEPTH / GLUT_STENCIL / GLUT_ACCUM
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node12.html

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Program detail 2/5

• void glutInitWindowPosition(int, int)
• void glutInitWindowSize(int, int)
• Initializing the window position and size when
  created.
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node11.html
• int glutCreateWindow(char)
• Open a window with previous settings.
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node16.html383

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Program detail 3/5

• Handling window and input events
• void glutDisplayFunc(void (func)(void))
• Called whenever the contents of the windows need
  to be redrawn.
• Put whatever you wish to draw on screen here.
• Use glutPostRedisplay() to manually ask GLUT to
  recall this display function.
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node46.html
• void glutReshapeFunc(void (func)(void))
• Called whenever the window is resized or moved.
• You should always call glViewport() here to
  resize your viewport.
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node48.html

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Program detail 4/5

• Other call back functions
• void glutKeyboardFunc(void (func)(unsigned char
  key, int x, int y))
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node49.html
• void glutMouseFunc(void (func)(int button, int
  state, int x, int y))
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node50.html
• void glutMotionFunc(void (func)(int x, int y))
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node51.html
• void glutIdleFunc(void (func)(void))
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node63.html
• See OpenGL Programming Guide Appendix D for more
  detail.

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Program detail 5/5

• Running the program
• void glutMainLoop(void)
• Enter the GLUT processing loop and never return.

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GLUT objects

• GLUT provides the follow objects
• Sphere, cube, torus, icosahedron, ocrtahedron,
  tetrahedron, teapot, dodecahedron, cone.
• Both wireframe and solid
• Ex glutSolidSphere(1.0, 24, 24)
• Ex glutWireCube(1.0)
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node80.htmlSECTION000120000000000000000

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OpenGL program -2 1/2

• include ltGL/glut.hgt
• void GL_display()
• glClearColor(0.0f, 0.0f, 0.0f, 0.0f)
• glClear(GL_COLOR_BUFFER_BIT)
• glBegin(GL_POLYGON)
• glColor3d(1.0f, 1.0f, 1.0f)
• glVertex3f(-1.0f, -1.0f, 0.0f)
• glColor3d(1.0f, 0.0f, 0.0f)
• glVertex3f(1.0f, -1.0f, 0.0f)
• glColor3d(0.0f, 1.0f, 0.0f)
• glVertex3f(1.0f, 1.0f, 0.0f)
• glColor3d(0.0f, 0.0f, 1.0f)
• glVertex3f(-1.0f, 1.0f, 0.0f)
• glEnd()
• glFlush()

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OpenGL program -2 2/2

• void GL_reshape(GLsizei w, GLsizei h)
• glViewport(0, 0, w, h)
• glMatrixMode(GL_PROJECTION)
• glLoadIdentity()
• glOrtho(-2.0f, 2.0f, -2.0f, 2.0f, -2.0f, 2.0f)
• glMatrixMode(GL_MODELVIEW)
• glLoadIdentity()
• void main(int argc, char argv)
• glutInit(argc, argv)
• glutInitDisplayMode(GLUT_SINGLE GLUT_RGB)
• glutInitWindowSize(250, 250)
• glutInitWindowPosition(100, 100)
• glutCreateWindow("Drawing sample")
• glutDisplayFunc(GL_display)
• glutReshapeFunc(GL_reshape)
• glutMainLoop()

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Data type
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Clear the buffers 1/2

• void glClearColor(GLclampf, GLclampf, GLclampf,
  GLclampf )
• Set the current values for use in cleaning color
  buffers in RGBA mode.
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc01_0rhu.asp
• void glClearDepth(GLclampd)
• Set the current values for use in cleaning depth
  buffer.
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc01_4j1k.asp

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Clear the buffers 2/2

• void glClear(GLbitfield)
• Clear the specified buffers to their current
  clearing values.
• GL_COLOR_BUFFER_BIT
• GL_DEPTH_BUFFER_BIT
• GL_ACCUM_BUFFER_BIT
• GL_STENCIL_BUFFER_BIT
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc01_8koi.asp

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Color representation

• RGBA red, green, blue, alpha
• Each channel has intensity from 0.01.0
• Values outside this interval will be clamp to 0.0
  or 1.0
• Alpha is used in blending and transparency
• Specify a color
• glColor34sifdv()
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc01_62b6.asp

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Points, Lines and Polygons 1/5

• Describe points, lines, polygons
• void glBegin(GLenum)
• Marks the beginning of a vertex-data list
• The mode can be any of the values in next page
• void glEnd()
• Marks the end of a vertex-data list
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc01_9u3y.asp

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Points, Lines and Polygons 2/5
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Points, Lines and Polygons 3/5
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Points, Lines and Polygons 4/5

• Specifying the vertices
• glVertex234sifdv()
• Specifies a vertex for use in describing a
  geometric object
• Can only effective between a glBegin() and
  glEnd() pair
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc03_2kag.asp

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Points, Lines and Polygons 5/5

• Specifying others
• glNormal() , glColor(), glIndex(),
  glTexCoord(), glMaterial()
• These commands should always be called before
  glVertex()

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Completion of drawing 1/2

• void glFlush()
• Forces previously issued OpenGL commands to begin
  execution.
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc02_8sa0.asp
• void glFinish()
• Forces previous issued OpenGL commands to
  complete.
• http//msdn.microsoft.com/library/default.asp?url
  /library/en-us/opengl/glfunc02_3aqw.asp

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Completion of drawing 2/2

• void glutSwapBuffers()
• Swap front and back buffers.
• http//www.opengl.org/resources/libraries/glut/spe
  c3/node21.html