Interactive Graphics Programming: Introduction and Chapter 1

1. Goals • Give student some idea what this class is about • Start Event Driven Programming if possible 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 • 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 • 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 notours! • 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 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 • Select interested ones to service • 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