1. Goals Give student some idea what this class is about
Start Event Driven Programming if possible
By programming with simple “language”, understand some existing algorithm, appreciation for algorithm design/development, tool: take home
Intro and Chapter 1

2. What is this class about
Building interactive graphics applications
Ask:
"What is interactive"?
real time
"What is graphics"?
visualization of geometry
human as IO device
Intro and Chapter 1

3. What is non-interactive application?
Show ray tracer and output
BumpScene/color.jpg - the color file
BumpScene/CommandFile.Bump - to bump the file
BumpScene/BumpImage.Color.jpg - color rendered image
BumpScene/BumpImage.BumpOut.jpg - bumped file
sacrifice time for quality (always true)
animated movies are not done with "real time interactive"
Intro and Chapter 1

4. Results: Demo Demo a couple of previous year's project
FORMS! need to sign form to have projects posted.
major difference with simple games: we do LOTS of unnecessary work!!. e.g.,
transformation
multiple views
real collision
proper software architectural structure
Our projects also lack in fun!
Intro and Chapter 1

5. Results: Expectations
Past good students get job at games company:
Difficult to get graphics (or game) specific jobs
This is A LOT of work!
Make sure you understand each assignment!
the assignments build on each other)
Large source code
it helps if you like programming!
Intro and Chapter 1

6. Our approach: Learn concepts (transformation) See how implemented You:
Use the implementation in more complex applications
Implement some of the concepts not shown in tutorials
Intro and Chapter 1

7. Language and API Language: JavaScript GUI API: HTML5 + AngularJS
Java, C#, C++
trick is lanaguge, GUI and Graphics API are tightly related.
GUI API: HTML5 + AngularJS
WinForm (for C#), MFC/WPF (C++),
GLUT/FLTK (OpenGL)
Swing (Java)
Graphics API: WebGL
D3D: C++ and Microsoft
OpenGL: C++ the rest of the world
XNA Framework or MonoGame (only with C#)
Intro and Chapter 1

8. Tutorials:
Start simple (few files) builds up over the quarter (100+ files)
Most of the code will be provided to you
In the forms of software library:
We will build this over the quarter
Intro and Chapter 1

9. Provided source code:
You NEED to understand the implementation of the source code provided to you!
If your program does not work because of the library:
it is your fault!
Source is provide for you, you should fix the problem!
Intro and Chapter 1

10. Learning from source code:
User of source code
Learn how to build applications by calling the provided functions
Evaluator of the source code
Use the provided source code, and
Evaluate: what is good, why is it bad
Developer of your own system
Use the provided source as an example prototype
Develop your own supporting library
MOST REWARDING! Time demanding!
Intro and Chapter 1

11. Let begin! Ball shooting program (Tutorial 5.6)
Ask ourselves, what are needed to implement this program?
Intro and Chapter 1

12. Control driven programs
Intro and Chapter 1

13. More detailed parsing …
Intro and Chapter 1

14. Concerns Complexity of our code Efficiency Number of events!
Un-handled events! (expose, iconize, …)
Efficiency
constantly waiting for the user
Repeating of similar work across applications (e.g., iconize)
Intro and Chapter 1

15. Event driven programming
No notion of main() function!
Instead: have a MainEventLoop() function …
Intro and Chapter 1

16. Main Event Loop
Intro and Chapter 1

17. Interesting differences
MainEventLoop() is not ours!
We as programmer, we cannot change this function!!
Instead, we have to program _with_ this function!
What happens at Label A? and
How to define “service routine”?
Interesting points:
Label B: loop forever!!
When will your program ever quit?
Label C: wait (instead of busy loop)
Label D: every event has a default action
Intro and Chapter 1

18. Event Driven Program
Intro and Chapter 1

19. Pseudo Code …
Intro and Chapter 1

20. Event Program structure
Application State
Well defined
Persist over function calls
Service of Events
To change the application state
Optional: kind of nice to have
displaying of application state
Intro and Chapter 1

21. Event: Origin and Handling
Operating System and Window Manager
Windows (Integrated system)
Unix + X Windows with twm, mwm, etc.
GUI API
Graphical User Interface
Application Programming Interface
Define GUI Element for handling events
Intro and Chapter 1

22. GUI Elements: Virtual/Abstract IO devices
Windows, Buttons, Slider bars, etc.
Associated with each GUI element, there are a set of defined events:
E.g., Button: click, release, double click, etc.
E.g., Window: mouse over, mouse move, etc.
As programmer, we can:
Ignore events from a GUI element or
Service events from a GUI element
Intro and Chapter 1

23. Events:Categories User: generated events Application generated events
Application specific: LMB click/drag
We should service this
General: iconize
Window manager will service this
Application generated events
Timer: we should service this
External:
GUI state change:
E.g., SystemInitialization()
Select interested ones to service
Window Environment:
E.g., Exposure
Request Collaboration:
E.g., Redraw events
Must service!
Intro and Chapter 1

24. Event Service registration
Callback function registration (A2)
Define the call back functions (D1)
Intro and Chapter 1

25. Event Service Routines
Service one state and return
Stateless!!
Should not contain presistent variables
Verify invocation conditions
Error checking
Our tutorials has serious problem with lack of error checking!!
Intro and Chapter 1

26. Event Service: Ball Shoot
Application state + Registration
Intro and Chapter 1

27. Event service: Ball shoot
Intro and Chapter 1