Computer Graphics

1
Computer Graphics

• Lee Byung-Gook

2
OpenGL

• Most Widely Adopted Graphics Standard
• High Visual Quality and Performance
• Industry standard, Reliable and portable
• Stable, Easy to use and Well-documented

3
OpenGL software libraries
4
Software libraries

• OpenGL provides most of the graphics
  functionality
• GLU provides support for some additional
  operations and primitive types, and is
  implemented using OpenGL function calls
• glut designed specifically to be used with
  OpenGL and it takes care of things like opening
  windows, redraw events, and keyboard and mouse
  input. It effectively hides all the windowing
  system dependencies for OpenGL

5
Installing OpenGL for Windows

• bundled with Win98, Win95, WinNT or download it
  
• look for dynamically-linked libraries (dlls)
• C\Winnt\system32\Opengl32.dll on Windows NT
• C\Windows\system\Opengl32.dll on Windows 95
• look for header files, e.g., for Visual C
• C\Program Files\Microsoft Visual
  Studio\VC98\include\gl\.h

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Installing glut for Windows

• http//www.opengl.org/developers/documentation/glu
  t.html?glutfirst_hit
• glut.h
• C\Program Files\Microsoft Visual
  Studio\VC98\include\gl\glut.h
• glut32.lib
• C\Program Files\Microsoft Visual
  Studio\VC98\lib\glut32.lib
• glut32.dll
• C\Windows\system32\glut32.dll on Windows 95, 98
• C\WINNT\system32\glut32.dll on Windows 2000, NT

7
Compiling with Visual C

• Start Visual C
• Choose File ? new, then from the Projects tab
  select Win32 Console Application
• Assign the project a name (lab00' for example),
  and choose a directory where the project files
  will be stored
• Choose File ? new, then from the Files tab
  select  C Source File
• Assign the file a name, lab00' for example. The
  .cpp extension will be added for you.
• Fill in the file lab00.cpp

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lab00.cpp

• // lab00.cpp, Computer Graphics,
  lbg_at_dongseo.ac.kr
• include ltGL/glut.hgt
• void myDisplay(void)
• glClearColor (.75, .75, .75, 0.0)
• glMatrixMode(GL_PROJECTION)
• glOrtho(0, 500, 0, 500, -1, 1)
• glMatrixMode(GL_MODELVIEW)
• glClear(GL_COLOR_BUFFER_BIT)
• glColor3f(0.60, .40, .70)
• glBegin(GL_POLYGON)
• glVertex2i(450, 250)
• glVertex2i(412, 367)
• glVertex2i(312, 440)
• glVertex2i(188, 440)
• glVertex2i(88, 368)
• glVertex2i(50, 250)
• glVertex2i(88, 132)

void main(int argc, char argv) glutInit(argc
,argv) glutInitDisplayMode (GLUT_SINGLE
GLUT_RGB) glutInitWindowSize(500,500) glutInit
WindowPosition(0,0) glutCreateWindow("lab00")
glutDisplayFunc(myDisplay) glutMainLoop()
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Compiling with Visual C

• Choose Project ? Settings and select the C/C
  panel. Enable Generate browse info.
• Select the Link panel. At the beginning (or
  anywhere) of the Object/library modules entry,
  add the libraries opengl32.lib and glut32.lib.
  Accept all the project setting changes by
  choosing OK.

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Compiling with Visual C

• Choose Build ? Build lab00.exe, or simply hit the
  F7 key in order to compile and link.
• A successful compilation would have produced the
  following output in your 'build' window
• ------------Configuration lab00 - Win32
  Debug----------- Compiling... lab00.cpp
  Linking... lab00.exe - 0 error(s), 0 warning(s)

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Compiling with Visual C

• If there are errors, hitting F4 will take you to
  the location of the first error message in the
  code, and thereafter always take you to the next
  error message.  Or, one can double click on any
  error message to jump to the relevant source
  code.
• Once the code has successfully compiled and
  linked, Build-Execute or Ctrl-F5 will run the
  code, as will double-clicking on the test.exe
  icon (found in the Debug directory) from a file
  browsing window.

12
Basic drawing

• OpenGL is a "state" machine Once it is in a
  state, it stays in that state until the state is
  changed.
• Basic commands
• glClearColor(red, green, blue, 0.0)
• // sets background color
• glClear(GL_COLOR_BUFFER_BIT)
• // clears the window to the background color
• glColor3f(red, green, blue)
• // values between 0.0 (no color) 1.0 (full
  color)
• glBegin()
• // determines how vertices are interpreted

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Basic drawing

• glVertex2i(412, 367)
• glVertex2i(312, 440)
• glVertex2i(188, 440)
• glVertex2i(88, 368)
• glVertex2i(50, 250)
• glVertex2i(88, 132)
• glVertex2i(188, 60)
• glVertex2i(312, 60)
• glVertex2i(412, 132)
• glEnd()
• // clears the state initiated by

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Colors

• 1.0f, 0.0f, 0.0f //red
• 0.0f, 1.0f, 0.0f //green
• 0.0f, 0.0f, 1.0f //blue
• 1.0f, 1.0f, 0.0f //yellow
• 1.0f, 0.0f, 1.0f //magenta
• 0.0f, 1.0f, 1.0f //cyan
• 1.0f, 1.0f, 1.0f //white
• .25f, .25f, .25f //dark gray
• .75f, .75f, .75f //light gray
• .60f, .40f, .12f //brown
• .60f, .40f, .70f //barney purple
• .98f, .625f, .12f //pumpkin orange
• .98f, .04f, .70f //pastel pink

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Drawing primitives

• OpenGL supports several basic primitive types,
  including points, lines, quadrilaterals, and
  general polygons. All of these primitives are
  specified using a sequence of vertices.
• glBegin and glEnd delimit the vertices that
  define a primitive or a group of like primitives.
  
• GL_POINTS Treats each vertex as a single point.
  Vertex n defines point n. N points are drawn.

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Drawing primitives

• GL_LINES Treats each pair of vertices as an
  independent line segment. Vertices 2n-1 and 2n
  define line n. N/2 lines are drawn.
• GL_LINE_STRIP Draws a connected group of line
  segments from the first vertex to the last.
  Vertices n and n1 define line n. N-1 lines are
  drawn.
• GL_LINE_LOOP Draws a connected group of line
  segments from the first vertex to the last, then
  back to the first. Vertices n and n1 define line
  n. The last line, however, is defined by vertices
  N and 1. N lines are drawn.

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Drawing primitives

• GL_TRIANGLES Treats each triplet of vertices as
  an independent triangle. Vertices 3n-2, 3n-1, and
  3n define triangle n. N/3 triangles are drawn.
• GL_TRIANGLE_STRIP Draws a connected group of
  triangles. One triangle is defined for each
  vertex presented after the first two vertices.
  For odd n, vertices n, n1, and n2 define
  triangle n. For even n, vertices n1, n, and n2
  define triangle n. N-2 triangles are drawn.
• GL_TRIANGLE_FAN Draws a connected group of
  triangles. One triangle is defined for each
  vertex presented after the first two vertices.
  Vertices 1, n1, and n2 define triangle n. N-2
  triangles are drawn.

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Triangle
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Drawing primitives

• GL_QUADS Treats each group of four vertices as an
  independent quadrilateral. Vertices 4n-3, 4n-2,
  4n-1, and 4n define quadrilateral n. N/4
  quadrilaterals are drawn.
• GL_QUAD_STRIP Draws a connected group of
  quadrilaterals. One quadrilateral is defined for
  each pair of vertices presented after the first
  pair. Vertices 2n-1, 2n, 2n2, and 2n1 define
  quadrilateral n. N/2-1 quadrilaterals are drawn.
  Note that the order in which vertices are used to
  construct a quadrilateral from strip data is
  different from that used with independent data.
• GL_POLYGON Draws a single, convex polygon.
  Vertices 1 through N define this polygon.

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Quad
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Basic primitives

• GL_LINES, GL_LINE_STRIP

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Basic primitives

• GL_LINE_LOOP, GL_TRIANGLES

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Basic primitives

• GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN

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Basic primitives

• GL_QUADS, GL_POLYGON

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OpenGL Naming Convension

• gl gl library
• Vertex command
• 2f number and type of parameters
• OpenGL Data Type Presentation C-language
• GLbyte 8-bit integer signed char b
• GLshort 16-bit integer short s
• GLint, GLsizei 32-bit integer long l
• GLfloat,GLclampf 32-bit float float f
• GLdouble,GLclampd 64-bit float double d
• GLubyte,GLboolean 8-bit unsigned unsigned
  char ub
• GLushort 16-bit unsigned unsigned short us
• GLuint,GLenum 32-bit unsigned unsigned long ui

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• glVertex234b s i f d ub us uiv()
• // allows 2 (x,y), 3 (x,y,z), or 4 (x,y,z,w)
  values
• // allows the following data types
• // b signed char 8 bit integer
• // s short 16 bit integer
• // i integer 32 bit integer
• // f float 32 bits
• // d double 64 bits
• // ub unsigned byte 8 bits
• // us unsigned short 16 bits
• // ui unsigned int 32 bits
• // optional v ? defined in an array (vector)

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lab01.cpp

• // lab01.cpp, Computer Graphics,
  lbg_at_dongseo.ac.kr
• include ltstdio.hgt
• include ltstdlib.hgt
• include ltGL/glut.hgt
• GLint windowWidth, windowHeight, N4
• void myAxis(void)
• int i
• glColor3f(0.98, .04, .70)
• glBegin(GL_LINES)
• for(i1 iltN i)
• glVertex2i(iwindowWidth/N, 0)
• glVertex2i(iwindowWidth/N, windowHeight)
• glVertex2i(0, iwindowHeight/N)
• glVertex2i(windowWidth, iwindowHeight/N)

void myDraw(void) glColor3f(0.60, .40, .70)
glBegin(GL_POLYGON) glVertex2i(windowWidth/N,
windowHeight/N) glVertex2i(3windowWidth/N,
windowHeight/N) glVertex2i(3windowWidth/N,
3windowHeight/N) glVertex2i(windowWidth/N,
3windowHeight/N) glEnd() void
myDisplay(void) glClear(GL_COLOR_BUFFER_BIT)
myAxis() myDraw() glFlush()
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lab01.cpp

• void myReshape(int width, int height)
• glClearColor (.75, .75, .75, 0.0)
• glViewport(0,0,width,height)
• glMatrixMode(GL_PROJECTION)
• glLoadIdentity()
• glOrtho(0, width, 0, height, -1, 1)
• windowWidthwidth
• windowHeightheight
• glMatrixMode(GL_MODELVIEW)
• void main(int argc, char argv)
• glutInit(argc,argv)
• glutInitDisplayMode (GLUT_SINGLE GLUT_RGB)
• glutInitWindowSize(500,500)
• glutInitWindowPosition(0,0)
• glutCreateWindow("lab01")

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Lab 01
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Lab 0101, 0102

• Homework1 in two weeks

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Lab 0103, 0104
32
Lab 0105, 0106
33
Lab 0107, 0108
34
Lab 0109