Dr' Scott Schaefer

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Computer Graphics CPSC 441

• Dr. Scott Schaefer

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Staff

• Instructor
• Dr. Scott Schaefer
• HRBB 527B
• Office Hours W 1030am-1130am
• Th 200pm-300pm
• (or by appointment)
• TA
• Ruoguan Huang
• HRBB 525
• Office Hours T 200pm-400pm
• F 1000am-noon

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Why did you take this class?
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Games
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Movies
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Visualization
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Industrial Design
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What will you learn in this class?

• 2D Graphics
• Drawing lines, polygons
• Fractals
• 3D Graphics
• Transformations
• Lighting
• Ray Tracing
• Solid Modeling
• Splines/Subdivision

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What youre expected to know

• Programming Experience
• Assignments in C/C
• Simple Mathematics
• Graphics is mathematics made visible

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How much math?

• General geometry/linear algebra
• Matrices
• Multiplication, inversion, determinant
• Vectors
• Dot product, cross product, linear independence

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First Homework Assignment!

• Linear Algebra Test
• http//projects.cs.tamu.edu/keyser/LAtest/
• Complete before September 16, 2009
• Take as many times as you like
• Must get at least 90 correct
• Grade ActualGrade (exam 90 ? 1 0 )

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Other Assignments

• Simple Painting Program
• Polygon Drawing and Clipping
• Fractals and Iterated Affine Transformations
• 3D Rasterization and Hidden Surfaces
• Ray Tracing

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More on Assignments

• Turn in code via CSNET
• (get an account if you dont already have one)
• Due by 1159pm on day specified
• Code, solution file and Win32 executable
• Make your code readable (comment)
• You may discuss concepts, but coding is
  individual (no team coding or web)

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Grading

• 55 Assignments
• 15 Midterm
• 25 Final
• 5 Course Evaluation

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Late Policy

• Penalty m number of minutes late

100
80
60
percentage penalty
40
20
1
2
3
4
days late
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Required Textbooks
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Suggested Reading
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Introduction to OpenGL

• What is OpenGL?
• Computer-graphics API (application programming
  interface)
• Developed by SGI in 1992
• Efficient, streaming interface
• 250 function calls for drawing 2D and 3D
  graphics
• Hardware independent
• Operating system independent
• Direct3D alternative API from Microsoft

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Introduction to OpenGL

• What OpenGL is NOT
• No commands for windowing
• No commands for obtaining user input
• No commands for anything except drawing on the
  screen

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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

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A Smidgen of OpenGL Code
Sets the color for clearing the screen

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

Clears the screen
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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

Sets the current drawing color to white
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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

Sets the window coordinates to (0,0,-1) (1,1,1)
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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

Starts drawing a polygon
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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

Specifies the vertices of the polygon
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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

Ends the polygon
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A Smidgen of OpenGL Code

• include ltwhateverYouNeed.hgt
• Main()
• IntializeAWindowPlease()
• glClearColor (0.0, 0.0, 0.0, 0.0)
• glClear (GL_COLOR_BUFFER_BIT)
• glColor3f ( 1.0, 1.0, 1.0)
• glOrtho (0.0, 1.0, 0.0, 1.0, -1.0, 1.0)
• glBegin (GL_POLYGON)
• glVertex3f (0.25, 0.25, 0.0)
• glVertex3f (0.75, 0.25, 0.0)
• glVertex3f (0.75, 0.75, 0.0)
• glVertex3f (0.25, 0.75, 0.0)
• glEnd()
• glFlush()
• UpdateTheWindowAndCheckForEvents()

Flushes all commands to ensure polygon is drawn
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OpenGL Command Formats
glVertex3fv( v )
Prefix
Initial capital letters
Number of components
Data Type
Vector
b - byte ub - unsigned byte s - short us -
unsigned short i - int ui - unsigned int f -
float d - double
omit v for scalar form glVertex2f( x, y )
2 - (x,y) 3 - (x,y,z) 4 - (x,y,z,w)
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OpenGL Geometric Primitives

• All geometric primitives are specified by vertices

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OpenGL Drawing Functions

• glBegin (GL_POINTS)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_LINES)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_LINE_STRIP)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_LINE_LOOP)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_POLYGON)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_TRIANGLES)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p6)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_TRIANGLES_STRIP)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p6)
• glVertex2iv (p3)
• glVertex2iv (p5)
• glVertex2iv (p4)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_TRIANGLES_FAN)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glEnd()

P5
P6
P1
P4
P2
P3
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OpenGL Drawing Functions

• glBegin (GL_QUADS)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p3)
• glVertex2iv (p4)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glVertex2iv (p7)
• glVertex2iv (p8)
• glEnd()

P8
P1
P4
P5
P2
P6
P3
P7
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OpenGL Drawing Functions

• glBegin (GL_QUADS_STRIP)
• glVertex2iv (p1)
• glVertex2iv (p2)
• glVertex2iv (p4)
• glVertex2iv (p3)
• glVertex2iv (p5)
• glVertex2iv (p6)
• glVertex2iv (p8)
• glVertex2iv (p7)
• glEnd()

P8
P1
P4
P5
P2
P6
P3
P7
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OpenGL-Related Libraries

• GLU (OpenGL Utility Library)
• - Part of OpenGL
• - Provides higher-level drawing routines such as
• Spheres, NURBS, tessellators, quadric shapes,
  etc

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OpenGL-Related Libraries

• GLU (OpenGL Utility Library)
• - Part of OpenGL
• - Provides higher-level drawing routines such as
• Spheres, NURBS, tessellators, quadric shapes,
  etc
• GLUT (OpenGL Utility Toolkit)
• - perform system-level I/O with the host
  operating system
• - cross platform
• - portable windowing API
• - not officially part of OpenGL

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GLUT OpenGL Utility Toolkit

• Application Structure
• Configure and open window
• Initialize OpenGL state
• Register input callback functions
• render
• resize
• input keyboard, mouse, etc.
• Enter event processing loop

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Sample Program

• void main( int argc, char argv)
• glutInit (argc, argv)
• glutInitDisplayMode (GLUT_SINGLE GLUT_RGB )
• glutInitWindowSize (250, 250)
• glutInitWindowPosition (100, 100)
• glutCreateWindow ( "HELLO")
• init()
• glutDisplayFunc ( display )
• glutMainLoop()

/ OpenGL Initialization /
/ callback function /
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GLUT Callback Functions

• Routine to call when something happens
• window resized, user input, window needs drawing,
  etc
• Register callbacks with GLUT
• glutDisplayFunc( display )
• glutIdleFunc( idle )
• glutKeyboardFunc( keyboard )
• glutMouseFunc( mouse )

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Assignment 1 Simple OpenGL/GLUT Application

• Build a simple OpenGL/GLUT application
• Designed to get you started using OpenGL and
  callbacks for interaction
• Full description available on course webpage
• http//courses.cs.tamu.edu/schaefer/441_Fall2009