Sam Stokes on Game Programming using C#, Lua, XNA, XML, Zune, XBox and World of Warcraft

Have a happy 4th of July! Be Safe!

Fireworks were initially invented by the Chinese, and likely the medical protocol for missing hands from explosions followed shortly. 

In the United States July the Fourth represents the date of the signing of the Declaration of Independence, although the real date might have been July 2 depending on your legal point of view.  The making of “joyous” noise and so forth slowly became a tradition, with the slow communications and independent nature of the US in the early years slowed the adoption of the fireworks and parades.

If you are going to the beach, make sure that you enter the water in a manner that allows you to check out the new environment, and all waters, except pools, are renewed everyday.  I surf quite often, but I always, and I mean always do a quick wade out to check for sandbars, etc.  Please do the same.

Treating burns, and helping young children get through the burn treatments is an art, why? Quite simply it is because of the inability of young children to handle painkillers during the stretching of their skin while being treated.  See: Snowy game, VR goggles take burn victims' minds off of pain, this is the type of game that you could easily build using the C# Express and XNA Game Studio, unfortunately, WII and Playstation would force you to pay $10,000 for their development tools, and then pay for access to the console.

Bottom line: Be safe, have fun, celebrate Independence! no matter where you are.

XNA: Using Fonts in XNA 3.1

XNA 3.1

No difference in how to use Fonts in XNA 3.1 over XNA 2.0.  If you already know how to use text in your project, this won’t be a big help to you.  This article was written to try to look a little smarter than my previous blog may have made me look.

Using text in your XNA project

Using the previous Blog approach, was simple, but not elegant. 

It would be better to add text that indicates whether or not SpriteBatch is an abstract class or a base class.

In this case you will need to add an existing content resource to the project.  The image below shows you how to add the spritefont material to the content folder.  There is a link that gets you to a very clear way to implement text in your game project.  Over future blogs we will go over how to add text, scoring and so forth to your game. 

Follow the article on MSDN: How to Draw Text Use the diagram to the right to add the existing content templates, in this case Sprite Font.
Ok, now you have added the content resources what do you do? First you have to construct the objects from the base or abstract classes, the objects need to build the fonts/letters and the location of the fonts/letters construct/instantiate a SpriteFont object and in this case the object’s name is Font1 You will also need a way to place it on the gameboard.  The way you put it on the game board is through the construction/instantiation of the class Vector2, and the object that is constructed is named FontPos. SpriteFont is a sealed class which is a member of the Microsoft.Xna.Framework.Graphics, which is in the file named: microsoft.xna.framework.dll	public class Game1 : Microsoft.Xna.Framework.Game    {        GraphicsDeviceManager graphics;        SpriteBatch spriteBatch;        //Add the two lines below        SpriteFont Font1;        Vector2 FontPos;          //****************** Your code should look like:
Later in the code, the FontPos will be used to determine the HEIGHT and WIDTH of the pixels that make up the text that are being written on the screen In your test of whether or not spriteBatch is abstract or a base class, this test will function to change the screen red if spriteBatch is a class, and it will stay blue if it isn’t and write the message on the screen.

Back to building DLLs: Determining if a class is abstract or public

In the world of VS 2008 and VS 2010, as well as all of the older development tools from Microsoft, the creation of DLLs is fully supported.  But just how do we utilize the DLLs?  First for the concept of DLLs to make sense, we need to understand classes, so I am going over the concept of classes step by step, but in my usual random manner, I have to ask that you stick with it. 

In XNA, the SpriteBatch, for example, is it a public class or an abstract class.  I was able to determine this using this kind of flunky process, but it works and it is quick:

First I wanted to examine if SpriteBatch was an abstract class so I used the following code, using the basic XNA Template (File-New-C#-XNA Game Studio X.X – Windows Game) using the default name:

       protected override void Draw(GameTime gameTime)
        {
            //GraphicsDevice.Clear(Color.CornflowerBlue);

            var x = typeof(SpriteBatch);

            if (x.IsAbstract)
                GraphicsDevice.Clear(Color.Red);
            else
                GraphicsDevice.Clear(Color.Black);

            // TODO: Add your drawing code here          

Just cut and paste the code starting at the protected override void Draw(GameTime gameTime).  Press the F5 key, your “game” should should show a black gameboard, indicating that SpriteBatch is not an abstract class.

• Replace: x.IsAbstract
• With: x.IsPublic
• The code should look like:                

if (x.IsPublic)
      GraphicsDevice.Clear(Color.Red);
else
      GraphicsDevice.Clear(Color.Black);

In this case the gameboard becomes black, indicating that the SpriteBatch is a public class.

Which is kind of a dumb way to do the analysis, but I just wanted to do something that was quick and dirty. 

Although this code will work in .NET Frameworks 2.0, 3.0, 3.5, and 4.0, be a sport and install the latest version of XNA Game Studio 3.1, you will need to uninstall the earlier versions of XNA Game Studio for the XNA Game Studio 3.1 to install. 

In this Blog we experimented with how to determine if a class is abstract or not, and we used some crude instrumentation to do our test.  In a future blog, sometime in the future, I will cover how to use interfaces and why, these are like abstract classes but with important differences.

Halo 3 blamed for killing of parents in 2007

Agenda:

1. Ranting
2. Research Articles
3. Conclusion

Ranting

The defense attorneys and the prosecutors both made a statement that Halo 3 addiction was the basis for the murder, the problem is that Halo 3  was released in May 15, 2007, the murder occurred in Oct., 2007.  This seems a little quick for addiction to reach this level.  My initial comment was: "Get out of here..."

Take a look at the article “So-Called ‘Halo killer’ gets 23 to life”, the article states that:

“Both Petric's defense attorneys and prosecutors blamed the crime on the teen's "addiction" to the game Halo 3. His lawyers claimed that the teen had become obsessed with the game after playing it constantly while incapacitated for months following an injury. Pleading an insanity defense, they argued he would forgo food and sleep to play the game for up to 18 hours a day, creating a mental state where he didn't think death was permanent.

The judge even went on to state:

"I feel confident that if there were no such thing as violent video games, I wouldn't know Daniel Petric.”

For a judge to make this kind of statement is telling and an example of the judge using the "bench" as a bully pulpit, and it would not allowed in the court.  If you offered this type of judgement in the court, you might get questions like:

• Just where did the judge get his PhD in Psychology? 
• Or what is the judge’s experience in game design? 
• Does the judge have a medical degree in neuroscience? 

If Daniel Petric hadn’t played Halo 3 for 18 hours a day, he could have done the same thing with pornography, watching Taxi too many time (President Reagan’s shooter did), stalking a women, watching Law & Order then pretending they understand the law, and so forth.

To say that Halo 3 was the cause of the addiction, frankly really puts a little to much on Halo 3.  I don’t find it addictive at all, in fact, I have had to learn to play it to do demos and found that it was fun, then lost interest quickly after completing the self play successfully.  I did keep it online and really enjoyed designing using the forge.

Addictive personalities are a problem in many areas of life, but in game design we do want to make the games fun and immersive, that is the goal.  It is natural that addictive personalities will be attracted to playing games, gambling, etc.  The rest of us have fun and move on. Sometimes addictive personalities lead society to better things, no clear examples, on the other hand, if they are failures, we look at them as losers who need a shower, and dental work.

In reading the ““So-Called ‘Halo killer’ gets 23 to life” I see this case as having some other elements, for instance, did Daniel Petric go through a process that altered his brain due to the use of painkillers during his recovery from an accident (in a separate article).  Maybe the painkillers mixed with the infinite game play Daniel Petric was doing caused the addiction.  Maybe his injury could have scrambled his brain.  

However, that isn't something that I can judge as I am not a neuroscientist, I don’t have a degree in Psychology, so according to the way courts work, I couldn’t have an opinion. But the judge did. 

I wonder if the judge did any research on game addiction.  I turned to the MS Library, the same digital library that colleges and universities would make available to their students, and I took a look to see if I can find any articles that might have researched the nature of addiction to games.

Research Articles:

From the article:

A bibliometric analysis of the scientific literature on Internet, video games, and cell phone addiction

• The image to the right shows all of the journals that carried addiction to ICT articles since 1996
• There were 582 articles that were written about some form of computer addiction 

Video Game Addiction in Children and Teenagers in Taiwan

This article is available for free inside of the Microsoft library, so you might be able to get it for free:

The object of the paper:

• To investigate current conditions of children and
  teenager’s game playing
• To explore differences in game addiction by gender,
  family functions, sensation seeking, and boredom
  inclination
• To test differences in animosity by different levels
  of addiction
• To discuss relationships among the factors of social
  skills and academic achievement by gender,
  family functions, sensation seeking, boredom inclination,
  animosity, and game addiction
• To test the path relationships among variables
  by using structure equation modeling (SEM)

Conclusion:

People get addicted to a range of things that most people may find:

• Interesting
• Fun
• Disgusting
• Boring
• Necessary
• Nannyism  

Bottom line to me, and I am not a lawyer, so it is my opinion:

• If the addicted person decides to harm another person or consume products that were created by harming others (such as child porn) then that person has to pay for their actions as judged lawfully by the society that was harmed by their actions. 
• Daniel Petric will pay for his actions with the loss of his freedom for 23 year, but it was his actions and not “Halo 3”, especially since Halo 3 wasn’t released till 2007 and the killing took place in 2004.  His actions didn’t happen because he was playing any computer game, his actions occurred because he is an independent human who made a very bad choice.

(Note: I made changes after the initial publication because I rechecked my facts, initially I had thought the murder took place in 2004 instead of 2007.  Something one can do on one owns blog.  If you see any "facts" that I have cited incorrectly let me know with comments, I think the reference to Taxi is correct.)

Links for Game Dev, VS 2010, Win7 Dev & Win7 Administration, with a touch of Workflow

Here are some helpful links for your development as a developer and software architect

A good blog that is written for educational purposes, but is a good example of a blog that a lot more technologists should emulate is Tamer Maher, a hard working Egyptian guy, see his blog at: http://tamermaher.spaces.live.com/

Now for the links of links, Ta-Da, and yes I used Bing to find these wonderful links!

Game Design

• XNA Creators Club Online
• XNA Developer Center
• Microsoft XNA Game Studio 3.1
• Upgrade Guide: XNA Game Studio 3.0 to XNA Game Studio 3.1
• MSDN XNA Game Studio 3.1
• MSDN XNA Game Studio 3.0
• Interactive Game Development (University of Houston, great STUFF!)
• Visual Basic and XNA
• Good tutorials Blue Rose Games
• Farseer physics engine for XNA (generally)
• Physics Helper for Silverlight, Blend and Farseer
• Farseer Physics Engine Simple Samples

VS 2010 Dev

• ">Visual Studio 2010 and .NET Framework 4 Training Kit - May Preview

Win7 Specific Application development articles

• Microsoft Application Compatibility Toolkit 5.5
• Windows 7 and Windows Server 2008 R2 Application Quality Cookbook

Database technologies

• Microsoft® SQL Server® 2008 Express with Advanced Services (you use this if you can't get the full version through your school, you do not need to download the Management Studio Release)
• Microsoft SQL Server Community Projects & Samples
• SQL Server 2008 Developer Training Kit
• SQL Server 2008 Security DataSheet
• Risk and Health Assessment Program for Microsoft SQL Server – Scoping Tool v1.1

Workflow and collaboration

• Project Trident: A Scientific Workflow Workbench
• myexperiment
• The Workflow Way: Understanding Windows Workflow Foundation
• Windows Workflow Foundation: Merchant Service Workflows
• Learning Workflow Foundation

Win7 Video Walkthroughs:

• BranchCache
• DirectAccess
• AppLocker
• Problem Steps Recorder
• BitLocker and BitLocker to Go
• Application Compatibility and User Account Control

Win7 Administration

• Windows 7 IT Pro Guides
• Deploying Virtual Desktop Pools by Using Remote Desktop Web Access Step-by-Step Guide
• Installing Remote Desktop Session Host Step-by-Step Guide
• Deploying Remote Desktop Web Access with Remote Desktop Connection Broker Step-by-Step Guide
• Remote Access Step-by-Step Guide: Deploying Remote Access with VPN Reconnect
• Step By Step Guide: Demonstrate DirectAccess in a Test Lab

DLL: Creating Objects or Concrete Classes

First off tip of the hat to Tamer Maher:

• Tamer Maher in Egypt suggested that I include links to the many game programming sites that I like, these will be included in the next posting of this blog. Thank you Tamer for your input! See his blog at http://TamerMaher.spaces.live.com where he discusses security!

Cy Khormaee and Bradley Jensen who will be joining their student teams to attend the Imagine Cup in Cairo, Egypt!  They will be joining my other teammates: Dan Waters, Clint Rutkas, and Diane Curtis.

Oops:

In the previous blog I said that we would go over how to use abstract classes.  I decided to discuss object instantiation from classes

How do you create or instantiate objects?

Now back to something that is entirely on track to using existing code and building code that you can share with others.

A few important points:

• A class and an object are different things.
• A class is a pattern that an object is built on, but it is not an object itself.
• An object is a concrete entity based on a class, and is instance of a class.
• The object is created through a process referred to as construction and instantiation

Objects can be created using the new keyword followed by the name of the class that the object will be based upon.

In C# you create the object from the class pattern by the code, written here where the object is given the same name as the class, in the following line of code, I show you the way that is more professional and easier to utilize:

Avatar Avatar = new Avatar();  //Can be confusing, but used in many examples

A better way to instantiate an object would be to give the instantiated object a separate but clear name:

Avatar BaldGuy = new Avatar();  //Less confusing and more descriptive

When an instance of a class is created (instantiate), a reference to the object is passed back to the programmer (the yellow arrow in the figure). In the example above, BaldGuy is a reference to an object based on Avatar. This reference refers to the new object, but does not contain the object data itself. In fact, you can create an object reference without creating an object at all:

Avatar BaldGuyA;

Creating object references that do not reference an object is a bad idea because it will fail at run time which occurs after you compile the program. This is an error that will not show up until you try to use your program.

However, such a reference can be made to refer to an object, either by creating a new object, or by assigning it to an existing object, like this:

Avatar BaldGuyB = new Avatar();

Avatar BaldGuyC = BaldGuyB;

• Two object references (BaldGuyB and BaldGuyC) refer to the same object (Avatar).
• Changes to the object made through BaldGuyB will be reflected in subsequent uses of BaldGuyC.
• Objects based on classes that are referenced (the process described) reference types of classes

Next Blog:

• Back to abstract classes and how to use them, differences between base classes, etc.

Going beyond:

• What is does Override mean?

DLLs: Create an Abstract Class the Derive a Class

We aren’t quite at the point where we can use DLLs, but we need to take a look at the concept of the abstract class and how to derive or construct the abstract class, you can derive or construct a “concrete” class as well, but that is usually well defined. 

An abstract class is a class that has to be derived or constructed by another class, it can’t instantiated by itself like a concrete class is able to.  This shows the C# approach, apologies to the Visual Basic reader.  Please feel free to add a comment with the VB approach.

Next blog, we will go over how to implement the abstract class, use it in the Derived Class.

If you want to get a head start, go to: How to: Define Abstract Properties.  Make sure to check the comments at the end of the article, there is a documentation bug and the comment fixes it.  The article assumes you know how to use the Visual Studio command line to compile.  Command line compiles are very useful, but can be tricky, I will cover this later.

You will see where this is going from the point of view of games, in fact this is very important stuff.  For XNA, F# and Silverlight games.

Heading to UCI for Senior Project Day!  June 10, 2009

Oh yeah, make sure to try Bing!

DLLs: Important stuff, and questions about Angelina Jolie’s use of DLLs

Original title for this blog:  

OMG: I appeared to have made a commitment to show how to build a dll in a previous blog and Angelina Jolie tells her story about DLLs

I am sorry, I made the statement:

• “In this blog, we will create a simple DLL that works in both Windows 7, Vista and the like, as well as on a Microsoft mobile device. “ 
  • What I meant to say was: “In a series of blog entries I will show you how to build a DLL that can be used in Windows 7, Vista and the like, as well as on a Microsoft mobile device…” 
  • My bad. 
  • Apologies.
• Oh the interview with Angelina Jolie didn’t happen, honestly, I didn’t even have the guts to ask.
• But I will tell you about DLLs.
• However, if Angelina used Windows, then she used DLLs, these are the atoms that drive Windows software development.  Hopefully that photo is “fair use” IP.
• WOW, she has skinny arms.

The Important stuff:

Back to DLLs, a way to store your programming stuff.  In one of the previous blogs, I talked about DLLs.  Let’s examine how the DLL is referenced in the Visual Studio environment.  To set a reference, in any of the Visual Studio tools you would use the reference and then right click it to add the DLL assembly reference to you IDE.  To add the reference to a DLL, you would right click on the reference for the project (you can have more than one project in a solution), select “Add Reference”, another dialog box opens.  One of the tabs you would select from the .NET tab, in the case of XNA, you might pick Microsoft.Xna.Framework.Pipeline, which isn’t selected by default when you start with building a new XNA project.  The following are brief explanations of the tabs:

.NET Tab

Lists all .NET Framework components available for referencing.

COM Tab

Lists all COM components available for referencing.  COM is a type of class library that has some added features and legacy features.  COM is only used in Windows and not Windows Mobile or Windows CE. 

Projects Tab

Lists Visual Studio projects in the current solution available for referencing. Select assemblies from this tab to create project-to-project references. This tab is used if you wish to reference another project either that are in the IDE or in the Projects Folder, you have to navigate the folder to find the DLL

Browse Tab

Allows you browse additional files to find a component not listed in the current tab and add it to the list.

Recent Tab

Displays recently added references.

Conclusion

Next blog will discuss how to use these references in your code.

Need help understanding C#, admit it, this isn’t easy

I have been working with software forever, ok, since I was 16, and I am 55 now.  So why ain’t I rich?  It’s a long and boring story, so stay focused…Oh wait a minute, I am pretty well off.  Software is the way to make money.  But you got to be willing to LEARN on your own and with your friends, schools can’t keep up.  If my discussion about DLLs was confusing, then take a look at this web site (I won’t tell): C# for Sharp Kids.  If you don’t understand how to use C#, you won’t be able to understand my discussions about XNA and programming mobile devices.

This is hosted completely on MSDN, and it is very well done online learning.  As you know from my writings on this blog, I bring up LINCOS from time to time, one of the early software languages that was designed as a language that could be used to communicate with aliens, space aliens that is.  This is the language that SCHEME is based on.

C# is based on another approach to software, one of the designers is Erik Meijer who is a really funny person, who is fun to hang around with.  He helped create the C# language.

The XNA Game Studio requires that you use C# to be able to use the XNA templates and to for your code to be loaded on the XBox 360.

As to classes and DLLs, please take a look at the C# for Sharp Kids link, I will start going over the DLLs at a high level, but want to make sure that you are up to speed with what a class is.  I will review what abstract classes, base classes and how to use them.

Building Mobile Games: Building a garage (DLL) for your stuff (classes)

Now that is a great title: Some more stuff.  Well that is what the blog is about: Stuff. 

Game stuff, to build a game, it is a good idea to understand the concept of DLL and classes.  DLL stands for Dynamic Linking Libraries, which is a library that contains classes that you can reuse.  DLLs are an important concept in object oriented programming, yet when I talk to students, there is often confusion about DLLs.  In this blog, we will create a simple DLL that works in both Windows 7, Vista and the like, as well as on a Microsoft mobile device.  What this blog entry won’t do is show the concept of interfaces, for that watch for a later blog in my random universe.  More on Interfaces can be found at Interfaces (C# Programming Guide) and MSDN Webcast: Architecting .NET Solutions with VB.NET

Think about DLLs as a storage place for your classes.  Other programs can call your DLL if you set up your DLL to be able to work with other programs.  This is the case for the many Windows DLL and for the system DLL.  You reference these programs in your program by setting references in the project IDE, there are other ways you can reference them as well. 

In the past, DLL suffered from a problem when the contract was broken by another program.  In .NET this was overcome by the use of assemblies.

Why use DLLs?  In a game, whether you are running it on the XBox, Windows or a Mobile device, you can modularize your program.  For example you could use a DLL to provide a physics solution for an XBox game, then you could reuse it with a Silverlight based game, and you might reuse in a game that works on a Mobile device, although it will have to allow for certain constraints with the Compact Framework.

The concept of DLLs is used both in Windows programming as well as Linux, see Anatomy of Linux dynamic libraries.  In the next posting I will work through a simple creation of a DLL and then use of the same DLL in several different types of projects.

Graphics programming on the Windows Mobile 6.0

It’s spinning triangle time!  In case the video on this page is too small, you can download the video from my codeplex site:

http://cool.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=27508, the codesnippets are located at this site as well.  In the video, I cover the following:

• Visual Studio Professional or Visual Studio Team Studio
• Which files to use for Windows Mobile programming
• Creating Graphics for the Windows Mobile platform
• How to use Code Snippets
• Deploying to the VS Mobile device emulator

I have decided to spend some time on programming games on the Windows Mobile, just for the heck of it.  I will use the cool codeplex site to store the builds and releases.

Class Diagram: Star Trek Enterprise as Love Boat

Using Class Diagrams

Check out the video to see how to use class diagrams!

Now I am thinking that this racing game, was a bad choice due to it’s requirement for excellent processing, and doesn’t run well on laptops in debug mode.  I initially started this series of blogs using a “gaming” machine that one of my neighbors had left with me while he was away.  When he got back, I had to give it back (he was trying to sell it to me).

When I tried it on my high end laptop running Vista, the game builds and runs slowly, although it really runs well on the XBox 360.  As a result not being about to run well on a high end laptop, I am going to have to sink of the Star Trek Enterprise as the Love Boat.  Well that is the nice thing about blogs, you don’t have to stick with an idea that sucks. 

However, this doesn’t mean that our use of the existing code in the Racing Game is over, I plan on striping out the physics code and using it in a more consistent discussion of racing physics.

For this entry, and I have been struggling with it for awhile, take a look at my video, where I discuss how to use Class Diagrams.

So for now, I am going to end the line of thought on the motorized bar chair and Star Trek Enterprise as a Love Boat.  The fun thing about blogs for me is that I can make those kinds of decisions.

Hope this has helped you out on understanding class diagrams.

Using cultural forces to illustrate physics: the new Star Trek Movie, the XNA Racing Game and a equation of a spring

Star Trek has long been the focus for games, and now with the new movie: “Star Trek: Love Boat”, there will be a lot of excitement again about Star Trek.  In previous posts I stated that we would examine the XNA Racing Game.  Then I went down the road with Bar Stool Racers.  You might well be asking yourself: So just how in the heck is Sam going to make that CONNECTION?  Well I had to contact Captain Randomness for assistance.  He couldn’t come by my house because the Post Office decided to CHANGE my street name, true story, and it wouldn’t come up in Google Maps.  Later when he realized that Live Maps were better, he will be by later.

Now how did this blog get the Racing Game, Bar Stool Racers and the Star Trek movie (which isn’t really about the conversion of the Enterprise into a Love Boat). 

I could be accused of being random.  It seems pretty easy to me that we could make those connections.  When you watch the trailers for the real Star Trek movie there is a motorcycle racing across some planet and then a Corvette, so it looks like a racing game is appropriate.  Then another trailer has asteroid like action, which we will go into depth about how to create a asteroid game.  Looks like we got two levels to me. 

But let’s keep on with the “Star Trek: Love Boat” theme for now.

Game Story: Single level, the crew of the Love Boat, Enterprise are suddenly trapped in a world by “Q” that requires that the guests must race bar stool carts to save one of the crewmembers from being forced to listen to Hubert Horatio Humphrey speeches for eternity, good politician, boring speaker.

Now on to the physics of ground vehicles, like cars or bar stool racers (which would parallel motorcycles).  From the diagram that I showed in a previous post, the Bar Stool Racer has an important spring component: The human in a sitting position acts like a spring.  The bar stool cart will fall over if the center of gravity moves to a certain point off the upright axis.  Strangely the spring constant is important for the feel of the game, and it is a simple physics principle with easy to write equation.

The equations of a spring is:

• f = –yk
  • where
    • f = force,
    • y = the position of the end of the spring,
    • k is a spring constant that is given to you by the spring manufacturer or you could determine it with fish scale.

With the respect to the car physics, the spring constant is 1.0, if you were developing simulations for a car manufacturer or test facility, you would have to do tests to determine what this constant for the automobile classes that you are testing.  Here is a code sample from the Car Racing Game:

public void Simulate(float timeChange)
        {
            // Calculate force again
            force += -pos * springConstant;
            // Calculate velocity
            velocity = force / mass;
            // And apply it to the current position
            pos += timeChange * velocity;
            // Apply friction
            force *= 1.0f - (timeChange * friction);
        }

In the next post I will show you how to use the class diagrams to examine your code.

New Game on the Creators Site! Zune game, with music!

Cool, Alien Game.  Designed for Zune, has music.  Sweet.  Check it out, download, show your friends.

Also, did you download the Racing game yet?  Make it happen.  Physics discussion coming up, reading the code.  So play with the racing game.

Yep, not writing code, reading code.  We all need to do more code reading.  There I said it.

The physics of Avatars

Ok, the Motorized (or Motorised for the English speaking) barstool is interesting because it is much like a go-cart which has a center of gravity as low as possible, except that the driver is riding quite a bit above the ground.  With the driver and their center of gravity acting like a pendulum creates an interesting equation of motions.

Now if we assume that the barstool is basically is an object that has a rider whose weight raises the center of gravity, and it acts like a weight on a stiff spring, we get the “humor” of watching a person who would be reckless enough to ride one of these vehicles.  Don’t try riding one of these on your own, but let’s stick with the design considerations of the physics of this vehicle.  Below I have drawn a diagram for one of the vehicles.  In study of statics the sum of forces should equal zero, in the study of dynamics the sum of forces can be non-zero.  For a game, the humor of the game is when the vehicle enters into a turn and overcomes the forces of friction of the wheels and the center of gravity no longer is directly over the centroid of the wheels (my definition of a centroid is the drawing of all the point forces that then yields a center point).

In the next entry I will go over the “static” or non-moving diagram of forces.

Schools in the Southern California region that have been invited to the Imagine Cup National Event in Boston are Cal State University, Los Angeles and Chapman University, so hopefully the teams will agree to attend.  All reasonable expenses are paid for the students.