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

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

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

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

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

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

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

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

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

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

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

Control driven programs Intro and Chapter 1

More detailed parsing … Intro and Chapter 1

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

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

Main Event Loop Intro and Chapter 1

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

Event Driven Program Intro and Chapter 1

Pseudo Code … Intro and Chapter 1

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

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

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

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

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

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

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

Event service: Ball shoot Intro and Chapter 1