Object Oriented Design

Goals  Feedback homework 8  Top Down Design: analyzing the requirements  Bottom Up Design: refactoring fundamental OpenGL functionality

The makings of the glutplane  Assumption: runtime environment is set up u Windows: GL4Java*.dlls installed u Mac: GL4Java*.zips installed in MRJClasses  Find file “glutplane.java” and “glutplane.html”  Install compile/link time environment u Windows: add GL4Java.jar to classpath u Mac: add GL4Java*.zips to project

Tools  Basic level tools u Javac (part of Sun’s JDK) u Jikes:  IDEs u Jbuilder (Windows, OS X) u CodeWarrior (Windows, OS X, OS 9, …)

Modify source  Edit “glutplane.java”  Replace 3 calls to add_plane(); with 20 calls u Hint: use a “for” loop instead of typing add_plane(); 20 times!  Compile/run/test  Upload binary files (.class) and.html file to Web server u glutplane.class u glutplane$planeobj.class u glutplane$glutplaneCanvas.class  Test applet on server  URL referring to html file.

More information  Provided by the Game Engine builders  /contra/installation.html /contra/installation.html  Chris Schenk:  Luke Swanson:

Top Down Requirement Analysis  Collect what the different applications/games need to have from the Game Engine  Danger: u Getting carried away u Creating specification that cannot be implemented (in time, within budget, …)

Requirement for Game engine  Camera aimed at character u Multiple cameras  Shapes  Aggregate shapes  Rotation of shapes and camera  Collision detection IIII  Clipping  Physics II u Particles  Text  Infinite backgrounds (repetitive textures, sky domes, …)  Foreground/messages/score keeping

Camera Control  Multiple cameras u Switching between cameras: no gui  Camera tracking (stay on object)  zoom  Multiple views at the same time  Independent control of camera

Shapes  Box, sphere, circle, rectangle, plane, line, point, cylinder, triangle strip,  Single / aggregate shapes  Rotation  Move in scene  Add textures to shape  Loading models u Load.obj files

Collision Detection iii  Detect collision of shapes and groups of shapes  Approximation with u spheres u Cubes

Clipping  no

Physics  Particles  Airplanes, skis, bikes  Simple gravity (would be nice)

Text  no

Backgrounds  Flat but repetitive  Sky domes, Sky boxes

Information panels  Score keeper  Output message  Dialogs (hard) u Use OpenGL, Swing or AWT?  Menus (hard) u Use OpenGL, Swing or AWT?

Bottom Up system design  Refactor existing functionality (the OpenGL mega blob) into service classes  Approach: look at instances of applications containing functionality that could be factored out of the application into a the middle ware layer => the Game Engine  Danger: u Feature oriented: contrast between cool and necessary functions

Refactoring textured square example  Basic structure of OpenGL application is give by init, display, and reshape  Look for code that, in generalized form could be pushed into game engine  => collect these operations and attributes in a class called glWindow

INIT  Collect a set of good initializations that make sense for most applications  Turn most features ON (lighting, texture mode)  In worst case application can overwrite or extend INIT

DISPLAY  Refactor display method into u preDisplay:  low level initializations that most applications would need anyway, e.g, clearing buffer.  Translating, rotating individual objects u mainDisplay: leave this to application to specialize u postDisplay:  Cleanup, error handling  Buffer swapping (to implement double buffering)

Factor out utility functions  Example: texture manager  Replace complex implementations of texture loading with single calls of texture managing functions located in middle ware (game engine)

Produce new application with middleware stuff removed

Homework  PROJECT: u Finish game proposal document u to Alex & Andri u Due: November 12  READING: u OpenGL Red book chapter 3; Viewing u u Due: November 12