1. “Computer Science is no more about computers than astronomy is about telescopes.”
Professor Edsger Dijkstra

2. OpenGL Notes & Guides

3. Required files for Windows
In the System Directory
glu32.dll
opengl32.dll
glut32.dll
In the C++ Include Directory
gl\gl.h
l\glu.h
gl\glaux.h (probably won't need it)
gl\glut.h (includes both gl.h and glu.h)
In the C++ Library Directory
gl\glu32.lib
l\opengl32.lib
gl\glaux.lib (probably won't need it)
gl\glut32.lib

4. OpenGL Libraries OpenGL Application GLU GL GLUT GLX Frame Buffer
Display

5. Event Loop OpenGL programs often run in an event loop:
Start the program
Run some initialization code
Run an infinite loop and wait for events such as
Key press
Mouse move, click
Reshape window
Expose event

6. OpenGL Command Syntax (1)
OpenGL commands start with “gl”
OpenGL constants start with “GL_”
Some commands end in a number and one, two or three letters at the end (indicating number and type of arguments)
A Number indicates number of arguments
Characters indicate type of argument

7. OpenGL Command Syntax (2)
`f' float
`d' double float
`s' signed short integer
`i' signed integer
`b' character
`ub' unsigned character
`us' unsigned short integer
`ui' unsigned integer

8. OpenGL Command Syntax (3)
“v” at the end of the name indicates a vector format.
Examples: glColor*()
glColor3b, glColor3d, glColor3f, glColor3i, glColor3s, glColor3ub, glColor3ui, glColor3us, glColor4b, glColor4d, glColor4f, glColor4i, glColor4s, glColor4ub, glColor4ui, glColor4us, glColor3bv, glColor3dv, glColor3fv, glColor3iv, glColor3sv, glColor3ubv, glColor3uiv, glColor3usv, glColor4bv, glColor4dv, glColor4fv, glColor4iv, glColor4sv, glColor4ubv, glColor4uiv, glColor4usv

9. OpenGL Primitives GL_POINTS GL_LINES GL_LINE_STRIP GL_LINE_LOOP
GL_TRIANGLES
GL_TRIANGLE_STRIP
GL_TRIANGLE_FAN
GL_QUADS
GL_QUAD_STRIP
GL_POLYGON

10. Scene Graph
Ground T1
Body T4 T2 T3
Head
Left Arm
Right Arm

11. OpenGL Program Organization
main:
find GL visual and create window
initialize GL states (e.g. viewing, color, lighting)
initialize display lists
loop
check for events (and process them)
if window event (window moved, exposed, etc.)
modify viewport, if needed
redraw
else if mouse or keyboard
do something, e.g., change states and redraw
redraw:
clear screen (to background color)
change state(s), if needed
render some graphics
change more states
render some more graphics .
swap buffers

12. glMatrixMode glMatrixMode C Specification Parameters Description
- specify which matrix is the current matrix
C Specification
void glMatrixMode( GLenum mode )
Parameters
mode Specifies which matrix stack is the target for subsequent matrix operations. Three values are accepted: GL_MODELVIEW, GL_PROJECTION, and GL_TEXTURE. The default value is GL_MODELVIEW.
Description
glMatrixMode sets the current matrix mode. mode can assume one of three values: GL_MODELVIEW Applies subsequent matrix operations to the modelview matrix stack. GL_PROJECTION Applies subsequent matrix operations to the projection matrix stack.

13. Viewing Pipeline

14. General 3D Viewing Pipeline
Modeling coordinates (MC)
World coordinates (WC)
Viewing coordinates (VC)
Projection coordinates (PC)
Normalized coordinates (NC)
Device coordinates (DC)

15. Virtual Camera Model Viewing Transformation Projection Transformation
The camera position and orientation is determined
Projection Transformation
The selected view of a 3D scene is projected onto a view plane

16. Viewing-Coordinate Parameters
Look-at point Pref
View-up vector V
N and V are specified in the world coordinates

17. Viewing-Coordinate Reference Frame
The camera orientation is determined by the uvn reference frame u v n

18. World-to-Viewing Transformation

19. Perspective-Projection View Volume
Viewing frustum
Why do we need near and far clipping plane ?

20. Normalizing Transformation
Transform an arbitrary perspective-projection view volume into the canonical view volume
Step 1: from frustum to parallelepiped

21. Normalizing Transformation
Transform an arbitrary perspective-projection view volume into the canonical view volume
Step 2: from parallelepiped to normalized

22. Orthographic Transformation
Preserves relative dimension
The center of projection at infinity
The direction of projection is parallel to a principle axis
Architectural and engineering drawings

23. OpenGL 3D Viewing Functions
Viewing-transformation function
glMatrixMode(GL_MODELVIEW);
gluLookAt(x0,y0,z0,xref,yref,zref,vx,vy,vz);
Default: gluLookAt(0,0,0, 0,0,-1, 0,1,0);
OpenGL orthogonal-projection function
glMatrixMode(GL_PROJECTION);
gluOrtho(xwmin,xwmax, ywmin,ywmax, dnear,dfar);
Default: gluOrtho(-1,1, -1,1, -1,1);
Note that
dnear and dfar must be assigned positive values
znear=-dnear and zfar=-dfar
The near clipping plane is the view plane

24. glViewport C Specification Parameters
void glViewport(GLint x, GLint y, GLsizei width, GLsizei height)
Parameters
x, y: Specify the lower left corner of the viewport rectangle, in pixels. The initial value is (0, 0).
width, height: Specify the width and height of the viewport. When a GL context is first attached to a surface (e.g. window), width and height are set to the dimensions of that surface.
glViewport specifies the affine transformation of x and y from normalized device coordinates to window coordinates. Let (xnd, ynd) be normalized device coordinates. Then the window coordinates (xw, yw) are computed as follows:

25. OpenGL 3D Viewing Functions
OpenGL perspective-projection function
The projection reference point is the viewing-coordinate origin
The near clipping plane is the view plane
Symmetric: gluPerspective(theta,aspect,dnear,dfar)
General: glFrustum(xwmin,xwmax,ywmin,ywmax,dnear,dfar)