OpenGL Tutorial CISC 640440 Computer Graphics

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OpenGL Tutorial CISC 640/440 Computer Graphics

• TA Qi Li/Mani Thomas
• qili_at_cis.udel.edu/manivt_at_cis.udel.edu

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Outline

• Submission policy
• OpenGL Basics and setup
• Draw geometry primitives
• Transformations in OpenGL
• Sample codes
• Office hour

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Submission Policy

• How to submit
• What to submit
• On late submission

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How to Submit

• Tar/zip file
• Unix
• gt tar -cf lastname_projectNum.tar projectDir
• gt gzip lastname_projectNum.tar
• Windows
• get a winzip application (if you don't have)
• go the directory storing your assignments
• right click your mouse to zip the directory
• Submit the tar/zip file through the course web
  (More details will be announced later)

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What to Submit

• Must contain
• readme
• Makefile
• Source codes
• Output figures (if any)
• Must NOT contain
• obj intermediate files
• obj data files

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What to Submit Readme

• My name
• My email myemail_at_udel.edu
• Project Num
• Part 1 description of this project
• This project is to apply xxx algorithm to
  plot xxx,
• Part 2 what I did and what I didn't do
• I completed all/most/some functionalities
  required in this project.
• The system is robust and the rendering is
  fairly efficient,
• I didn't do . The reason is .
• Part 3 What files contained
• Part 4 How to compile and how to run
• The project is developed in windows system
  and tested in stimpy (strauss) unix system,

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What to Submit Makefile for EECIS

• Makefile for EECIS
• uncomment the following line for the C
  compiler(cc)
• CC cc CC CC
• TOP /usr/local/mesa
• list the name of the executable you wish to
  produce
• exec hello
• list all your object files separated by spaces
  
• objects hello.o
• list all your header files separated by spaces
  
• includes lines5.h lines5_2.h
  
  
• LINKDIR -L(TOP)/lib -L/usr/openwin/lib
• INCLUDEDIR (TOP)/include
• LLDLIBS -lGL -lglut -lMesaGLU -lMesaGL -lm
  -lX11 -lXext -lXmu \ -lXt -lXi
  
• (exec) (objects)
• (CC) -o _at_ (LINKDIR) (objects) (LLDLIBS)
• (objects) (includes) (CC) -c -I(INCLUDEDIR)
  lt
• .PHONY clean
• clean -rm -f (objects) (exec)

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What to Submit Makefile for Composer

• Makefile for Composer/Strauss
• uncomment the following line for the C
  compiler(cc)
• CC cc CC CC
• TOP /home/base/usrb/chandrak/640/OpenGL/Mesa-2.6
  
• list the name of the executable you wish to
  produce
• exec hello
• list all your object files separated by spaces
  
• objects hello.o
• list all your header files separated by spaces
  
• includes lines5.h lines5_2.h
  
  
• LINKDIR -L(TOP)/lib -L/usr/openwin/lib
• INCLUDEDIR (TOP)/include
• LLDLIBS -lGL -lglut -lMesaGLU -lMesaGL -lm
  -lX11 -lXext -lXmu \ -lXt -lXi
  
• (exec) (objects)
• (CC) -o _at_ (LINKDIR) (objects) (LLDLIBS)
• (objects) (includes) (CC) -c -I(INCLUDEDIR)
  lt
• .PHONY clean
• clean -rm -f (objects) (exec)

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Late Submission

• N 10 percent of the points you got deducted if
  there are N (lt5) late days (not counting
  weekends). No acceptance for the submission more
  than 5-day late
• Each student has three free (i.e. without any
  penalty) late days for entire semester. You
  should notify the TA the use of free late days
  ahead

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Outline

• Submission policy
• OpenGL Basics and setup
• Draw geometry primitives
• Transformations in OpenGL
• Sample codes
• Office hour

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OpenGL What is It?

• GL (Graphics Library) Library of 2-D, 3-D
  drawing primitives and operations
• API for 3-D hardware acceleration
• GLU (GL Utilities) Miscellaneous functions
  dealing with camera set-up and higher-level shape
  descriptions
• GLUT (GL Utility Toolkit) Window-system
  independent toolkit with numerous utility
  functions, mostly dealing with user interface

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OpenGL Setup in Unix

• Unix (strongly recommended)
• add the following command in your .cshrc
• EECIS setenv
  LD_LIBRARY_PATH /usr/local/mesa/lib/usr/openwin/l
  ib
• Composor setenv LD_LIBRARY_PATH
  /home/usra/usrb/chandrak/640/OpenGL/Mesa-2.6/usr/
  openwin/lib
• Download Makefile (for hello.c)
• Makefile_eecis, or
• Makefile_composor
• remote display (If your local machine is not
  stimpy or strauss, you need to do the following)
• localmachine gt ssh stimpy.cis.udel.edu
• Compile stimpygt make
• Run stimpy gt hello

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OpenGL Setup in Windows

• Windows/VC 6.0
• Get glut http//www.xmission.com/nate/glut.html
• An excellent source for the setup of openGL on
  Windows/VC 6.0 is available at
• http//www.lighthouse3d.com/opengl/glut/index.php

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OpenGL Setup in Windows

• Windows (step 1 create new project)

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OpenGL Setup in Windows

• Windows (step 2 create new project)

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OpenGL Setup in Windows

• Windows (step 3 insert file)

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OpenGL Setup in Windows

• Windows (step 4 project setting)

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OpenGL Setup in Windows

• Windows (step 5 project setting)

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Outline

• Submission policy
• OpenGL Basics and setup
• Draw geometry primitives
• Transformations in OpenGL
• Sample codes
• Office hour

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OpenGL Geometric Primitives
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Specifying Geometric Primitives

• Primitives are specified using
• glBegin(primType)
• ...
• glEnd()
• primType determines how vertices are combined

GLfloat red, green, blue GLfloat x,
y glBegin(primType) for (i 0 i lt nVerts
i) glColor3f(red, green, blue)
glVertex2f(x, y) ... // change coord.
values glEnd()
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OpenGL Vertex/Color Command Formats
glVertex3fv( v )
glColor3fv( v )
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 e.g., glVertex2f(x,
y) glColor3f(r, g, b)
2 - (x,y) 3 - (x,y,z), (r,g,b) 4 -
(x,y,z,w), (r,g,b,a)
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Outline

• Policy
• OpenGL Basics and setup
• Draw geometry primitives
• Transformations in OpenGL
• Sample codes
• Office hour

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OpenGL 3-D coordinates

• Right-handed system
• From point of view of camera looking out
  into scene
• X right, -X left
• Y up, -Y down
• Z behind camera, -Z in front
• Positive rotations are counterclockwise around
  axis of rotation

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Transformations in OpenGl

• Modeling transformation
• Viewing transformation
• Projection transformation

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Modeling Transformation

• Refer to the transformation of models (i.e., the
  scenes, or objects)
• Generally,
• glMultMatrixf(M_i)
• Some simple transformations
• Translation glTranslate(x,y,z)
• Scale glScale(sx,sy,sz)
• Rotation glRotate(theta, x,y,z)
• x,y,z are components of vector defining axis of
  rotation
• Angle in degrees direction is counterclockwise

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Viewing Transformation

• Refer to the transformation on the camera
• Using glTranslate() and glRotate()
• Using gluLookAt()
• gluLookAt (eyeX, eyeY, eyeZ, centerX, centerY,
  centerZ, upX, upY, upZ)
• eye (eyeX, eyeY, eyeZ)T Desired camera
  position
• center (centerX, centerY, centerZ)T Where
  camera is looking
• up (upX, upY, upZ)T Cameras up vector

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Viewing Transformation
from Woo et al
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Projection Transformation

• Refer to the transformation from scene to image
• Orthographic projection
• glOrtho (left, right, bottom, top, near, far)

from Hill
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Projection Transformation

• Refer to the transformation from scene to image
• Orthographic projection
• glOrtho (left, right, bottom, top, near, far)
• Perspective projection
• glFrustum (left, right, bottom, top, near, far)

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Projection Transformation

• Refer to the transformation from scene to image
• Orthographic projection
• glOrtho (left, right, bottom, top, near, far)
• Perspective projection
• glFrustum (left, right, bottom, top, near, far)

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Notes on openGl transformations

• Before applying modeling or viewing
  transformations, need to set glMatrixMode(GL_MODE
  LVIEW)
• Before applying projection transformations, need
  to set glMatrixMode(GL_Projection)
• Replacement by either following
  commands glLoadIdentity() glLoadMatrix(M)
• Multiple transformations (either in modeling or
  viewing) are applied in reverse order

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Notes on openGl transformations

• Before applying modeling or viewing
  transformations, need to set glMatrixMode(GL_MODE
  LVIEW)
• Before applying projection transformations, need
  to set glMatrixMode(GL_Projection)
• Replacement by either following
  commands glLoadIdentity() glLoadMatrix(M)
• Multiple transformations (either in modeling or
  viewing) are applied in reverse order

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Outline

• Policy
• OpenGL Basics and setup
• Draw 2-D primitives
• Transformation in OpenGL
• Sample codes
• Office hour

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Sample codes

• void main(int, char)
• void init (void)
• void reshape (int, int)
• void display (void)
• void menu (void)
• void dda_line (int, int, int, int)
• void midpoint_line (int, int, int, int)
• void gl_line (int, int, int, int)
• void mouse (int, int, int, int)
• void keyboard (unsigned char, int, int)

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Sample code main function
int main (int argc, char argv) glutInit
(argc, argv) glutInitDisplayMode (GLUT_SINGLE
GLUT_RGB) glutInitWindowSize (400, 400)
glutInitWindowPosition (400, 350)
glutCreateWindow ("Scan Conversion
Algorithms") init () glutDisplayFunc
(display) glutReshapeFunc (reshape)
glutMouseFunc (mouse) glutKeyboardFunc
(keyboard) menu () glutMainLoop ()
return (0) / ANSI C requires main to return
int. /
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Sample code init
void init (void) / select clearing color
/ / this color is white --- full red,
green, and blue components / / the last
component is alpha(transparency) --- use zero /
glClearColor (1.0, 1.0, 1.0, 0.0)
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Sample code reshape
void reshape (int w, int h) / This routine
is called when the initial GL window is created
and when the window is resized. It is
followed in execution by the 'display'
routine. / / initialize viewing values /
glViewport (0, 0, (GLint) w - 1, (GLint) h - 1)
glMatrixMode (GL_PROJECTION) glLoadIdentity
() glOrtho (0.0, (GLdouble) w, 0.0, (GLdouble)
h, -1.0, 1.0)
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Sample code display
void display (void) / clear all pixels /
glClear (GL_COLOR_BUFFER_BIT) / don't wait!
start processing buffered OpenGL routines
/ glFlush ()
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Sample code gl_line
void gl_line (int x0, int y0, int x1, int y1)
glColor3ub (0, 255, 0) / green / glBegin
(GL_LINES) glVertex2i (x0, y0)
glVertex2i (x1, y1) glEnd ()
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Sample code mouse
void mouse (int button, int state, int x, int
y) switch (button) case
GLUT_LEFT_BUTTON if (state GLUT_DOWN)
printf ("x d, y d\n", x, y)
break case GLUT_RIGHT_BUTTON if
(state GLUT_DOWN) exit (0)
break default break
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Outline

• Policy
• OpenGL Basics and setup
• Draw 2-D primitives
• Transformation in OpenGL
• Sample codes
• Office hour

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Office hour of CISC640

• Monday 300-500pm Pearson 115B
• Email qili_at_cis.udel.edu
• Webpage http//www.cis.udel.edu/qili/

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Office hour of CISC440

• Wed 500-700pm Pearson 115B
• Email manivt_at_cis.udel.edu
• Webpage http//www.cis.udel.edu/manivt/