1. Outline Announcements Dynamic Libraries HWII on web, due Friday
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Dynamic Libraries

2. HW I Issues Some problems: cc -lm csin.c -ocsin
-l<name> tells compiler to find a library called “libname.a,” and get any routines it needs
-lm says to look for libm.a (or .so)
-lblas says to look for libblas.a (or .so)

3. HW I Issues 1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16 ?
Calling BLAS
Look on BLAS sheet for routines that do y<-Ax
nothing matches, but find several routines that solve y<-Ax+y
CALL SGEMV('n',m,n,1.0,C,MMAX,v,1, 0.0, PC, 1)
As a matrix, C is m-by-n, but as an array, it is MMAX-by-NMAX
BLAS needs both: MMAX (LDA) lets BLAS know where columns start
Also,  &  should be real (1.0 and 0.0, 1 and 0 won’t work on some systems) m
MMAX

4. BLAS Increments BLAS lets (makes) you specify an increment.
Allows you to use 2D arrays as vectors: 1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16 ?
INC=MMAX(6)
INC=MMAX+1

5. Why Add Graphics?
Writing graphics routines can be difficult (not as hard as you think, though)
There are many packages for scientific visualization (MATLAB, AVS, OpenDX)
So, why bother coding yourself?
Get a quick view of results
Make program accessible to non-specialists
It’s cool!

6. OpenGL OpenGL is the graphics library
Started as proprietary library on Silicon Graphics workstations
Now available everywhere (standard with most systems)
Tightly coupled with graphics cards
Underlying system for most games and scientific visualization systems

7. OpenGL Built-in primitives to draw points, lines, polygons
Can easily transform objects in 3D
scale, rotate, translate, change viewpoint
Can control opacity of objects, not just color
Can add textures to objects
For more info: or
CS417

8. OpenGL and GLUT OpenGL is a rich description of graphics operations
But, OpenGL needs to interact with system
needs windows to draw in
needs windows to recognize graphics commands
GLUT--Graphics Library Utility Toolkit
System independent library for creating windows and managing simple user interaction (mouse, keyboard, menus)
Can call from C (C++), FORTRAN, and now Java

9. GLUT Can build simple GUI’s with GLUT
for more sophisticated GUI’s consider Java or system-dependent tools
However, GLUT GUI’s demonstrate basic GUI ideas:
Developer writes Callbacks--routines that are executed upon user events:
Mouse click in window, keyboard input
The program tells GUI system which routines go with which events
Control is turned over to GUI system
GUI system calls Callback for corresponding event

10. Event-Driven Programming
Most scientific programs are simple
Read data
Compute something
Output answer
Quit
GUIs are fundamentally different
Start
Process mouse or keyboard
Do something
Repeat 1-3

11. Event-Driven Programming
GUIs have two key features
Never quit until user demands it
Process events
Suggests a simple structure
While(true){
Get next event
Determine event type
Action determined by type }

12. Event-Driven Programming
All GUIs regardless of OS and language do the same thing
Some systems require (allow) you more flexibility
Write event loop yourself
Parse events yourself
GLUT is not designed for writing “full-fledged” GUIs
GLUT has its own event loop
Hidden from you
GLUT allows you to “register” subroutines to handle a limited number of events.

13. GLUT Program Structure
GLUT Programs follow a simple structure
Create window(s)
Register subroutines to handle events
Turn control over to GLUT

14. GLUT and RAD1D
I added GLUT routines to RAD1D to plot C at several times
main:
Creates a window
Registers “DrawC” as “DisplayFunc”
DrawC is called when screen must be re-drawn
No inputs to display functions!
Registers “ResizeIt” as “ReshapeFunc”
ResizeIt(width,height) is called when window is resized
Calls RunRad
Original RAD1D main
Periodically calls AddC which stores current C in array GLC array
Gives control to GLUT

15. DrawC plots a line for every time observation of C stored in GLC
first line is red, last line is blue, color varies in between

16. Drawing with OpenGL GLUT creates windows and handles events,
Graphics in DrawC are produced by OpenGL
OpenGL is very powerful, but drawing is fairly simple
Set color:
glColor3f
Tell OpenGL you’re starting to draw:
glBegin(GL_LINE_STRIP);
Place several vertices:
glVertex2d (creates one vertex)
Tell OpenGL to stop drawing
glEnd();