Aerodynamics for Convex Hulls

I had quite a nice thought experiment and thought I'd document it for you guys to have a look at. I wanted to come up with a quick way to (semi) realistically simulate lift and drag on any shape. Such an engine could be used for flash games for example a hang glider game. Realism like this (if carefully implemented) can add a lot to a game.

I plan on implementing this in flash sometime after my exams are over, but some of you might be interested in my approach, so feel free to beat me to coding it!

Here is what I've got so far, you can click on a page to expand it in a lightbox (or click here to download the pdf):

Fun with Inverse Kinematics

In part to try out AXDT, a flash plugin for Eclipse (which you can find here), I decided to create a simple experiment involving Inverse Kinematics. This is not a very useful implementation but the results are quite fun. Essentially, the angles of subsections of  each kinematic chain are altered until they face the mouse. I quickly discovered this is not the best solution for IK, but just for fun I made a kind of windswept, fur or grass effect using about 200 IK chains. 

As usual click the top screenshot to launch the experiment and click here for source:

New Source Code Page

Hey guys,

Due to many requests being for source code I have added a source section to the blog. When my exams are over I'll work through adding source code to older projects but for now I've included a few from some new stuff I've been working on. Just click the tab at the top from anywhere to access it.

Happy flashing!

Sam

Update: Colourful Turtle

In my last experiment I recreated a turtle vector drawing program, with a simple interface. I'll post a small update to that which adds some color to the output. Here are some screenshots, as usual click the first one to launch the image, and source code can be found at the bottom, enjoy and let me know if you make anything pretty!

Source:

package org.experimentalized
{
 import flash.display.Sprite;
 import flash.events.Event;
 import flash.events.KeyboardEvent;
 import flash.display.Graphics;
 import flash.text.TextField;
 import flash.text.TextFieldType;
 import flash.geom.Rectangle;
 import flash.utils.getTimer;

 [SWF(width='550',height='550',backgroundColor='#000000',frameRate='30')]

 public class Turtle extends Sprite
 {
  private var commandstring:String = new String("mv:30,lt:90,mv:10,rt:30");
  private var S:Sprite = new Sprite();
  private var Angle:Number = new Number(0);

  private var X:Number = 0;
  private var Y:Number = 0;

  private var R:int = 0;
  private var G:int = 0;
  private var B:int = 0;


  private var input:TextField = new TextField();

  
  private function newrun(e:KeyboardEvent):void
  {
    commandstring = input.text;
    S.graphics.clear();
    S.graphics.lineStyle(1,0xFFFFFF);
    S.graphics.moveTo(0,0);
    Angle = 0;
    X = 0;
    Y = 0;
  }

  public function Turtle():void
  {
   addEventListener(KeyboardEvent.KEY_DOWN, newrun);
  
   addChild(S);

   input.width = 530;
   input.height = 20;
                 input.x = 10;
                 input.y = 10;
                 input.background = true;
                 input.backgroundColor = 0xFFFFFF;
   input.type = TextFieldType.INPUT;
   
   input.text = commandstring;


   addChild(input);

   S.x = 275;
   S.y = 200;
      
   this.addEventListener(Event.ENTER_FRAME, handler);
  }
  
  private function handler(e:Event):void
  {
   R = int(128 * (1 + Math.cos(getTimer()/1000-0.8981)));
   G = int(128 * (1 + Math.sin(getTimer()/7473-0.3812)));
   B = int(128 * (1 + Math.sin(getTimer()/1273+0.1787)));
   
   var C:uint = (R<<16|G<<8|B);   
   
   S.graphics.lineStyle(1,C);
   var commands:Array = new Array();
   commandstring = commandstring.split(" ").join("");
   commands = commandstring.split(",");
   var i:int;

   for(i=0;i<commands.length;i++)
   {
    if(commands[i].charAt(0)=="m")
    {
     var dist:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     X = X + dist*Math.cos(Angle);
     Y = Y + dist*Math.sin(Angle);
     S.graphics.lineTo(X,Y);
    }
    else if(commands[i].charAt(0)=="l")
    {
     var changeleft:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     Angle -= Math.PI*changeleft/180;
     if(Angle<0) Angle += 2*Math.PI;
    }
    else if(commands[i].charAt(0)=="r")
    {
     var changeright:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     Angle += Math.PI*changeright/180;
     if(Angle>Math.PI*2) Angle -= 2*Math.PI;
    }
   }
  

   //Resize to fit on the square after each iteration (purely aesthetic choice...)
   
   var Rect:Rectangle = S.getRect(S.parent);
   
   S.x += 275 - (Rect.x+Rect.width/2);
   S.y += 275 - (Rect.y+Rect.height/2);
   S.width = 550;
   S.height = 550;
  }
 }
}

Turtle: 30 minute experiment

I had recently been reminiscing about IT lessons in year 3 where we were allowed to play around with those Turtle vector drawing programs. I thought I'd write one and share the results as a quick break from revision. Although it can't do much at the moment (the only commands are forward, left and right) with a bit more work I'm sure it could be made into quite an exciting program. You'll find the source code below and as usual just click the top image to launch the experiment.

Source code:

package org.experimentalized
{
 import flash.display.Sprite;
 import flash.events.Event;
 import flash.events.KeyboardEvent;
 import flash.display.BitmapData;
 import flash.display.Bitmap;
 import flash.display.Graphics;
 import flash.text.TextField;
 import flash.text.TextFieldType;

 [SWF(width='550',height='400',backgroundColor='#000000',frameRate='30')]

 public class Turtle extends Sprite
 {
  

  private var commandstring:String = new String("mv:30,lt:90,mv:10,rt:30");
  private var S:Sprite = new Sprite();
  private var Angle:Number = new Number(0);

  private var X:Number = 0;
  private var Y:Number = 0;

  private var input:TextField = new TextField();

  
  private function newrun(e:KeyboardEvent):void
  {
    commandstring = input.text;
    S.graphics.clear();
    S.graphics.lineStyle(1,0xFFFFFF);
    S.graphics.moveTo(0,0);
    Angle = 0;
    X = 0;
    Y = 0;
  }

  public function Turtle():void
  {
   addEventListener(KeyboardEvent.KEY_DOWN, newrun);
  
   addChild(S);

   input.width = 530;
   input.height = 20;
                 input.x = 10;
                 input.y = 10;
                 input.background = true;
                 input.backgroundColor = 0xFFFFFF;
   input.type = TextFieldType.INPUT;
   
   input.text = commandstring;


   addChild(input);

   S.x = 275;
   S.y = 200;
   
   S.graphics.lineStyle(1,0xFFFFFF); 
   
   this.addEventListener(Event.ENTER_FRAME, handler);
  }
  
  private function handler(e:Event):void
  {
   var commands:Array = new Array();
   commandstring = commandstring.split(" ").join("");
   commands = commandstring.split(",");
   var i:int;

   for(i=0;i<commands.length;i++)
   {
    if(commands[i].charAt(0)=="m")
    {
     var dist:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     X = X + dist*Math.cos(Angle);
     Y = Y + dist*Math.sin(Angle);
     S.graphics.lineTo(X,Y);
    }
    else if(commands[i].charAt(0)=="l")
    {
     var changeleft:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     Angle -= Math.PI*changeleft/180;
     if(Angle<0) Angle += 2*Math.PI;
    }
    else if(commands[i].charAt(0)=="r")
    {
     var changeright:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     Angle += Math.PI*changeright/180;
     if(Angle>Math.PI*2) Angle -= 2*Math.PI;
    }
   } 
  }
 }
}

To make the output lines automatically fit the stage use the following instead:

package org.experimentalized
{
 import flash.display.Sprite;
 import flash.events.Event;
 import flash.events.KeyboardEvent;
 import flash.display.Graphics;
 import flash.text.TextField;
 import flash.text.TextFieldType;
 import flash.geom.Rectangle;

 [SWF(width='550',height='550',backgroundColor='#000000',frameRate='30')]

 public class Turtle extends Sprite
 {
  private var commandstring:String = new String("mv:30,lt:90,mv:10,rt:30");
  private var S:Sprite = new Sprite();
  private var Angle:Number = new Number(0);

  private var X:Number = 0;
  private var Y:Number = 0;

  private var input:TextField = new TextField();
  
  private function newrun(e:KeyboardEvent):void
  {
    commandstring = input.text;
    S.graphics.clear();
    S.graphics.lineStyle(1,0xFFFFFF);
    S.graphics.moveTo(0,0);
    Angle = 0;
    X = 0;
    Y = 0;
  }

  public function Turtle():void
  {
   addEventListener(KeyboardEvent.KEY_DOWN, newrun);
  
   addChild(S);

   input.width = 530;
   input.height = 20;
                 input.x = 10;
                 input.y = 10;
                 input.background = true;
                 input.backgroundColor = 0xFFFFFF;
   input.type = TextFieldType.INPUT;
   
   input.text = commandstring;


   addChild(input);

   S.x = 275;
   S.y = 200;
      
   this.addEventListener(Event.ENTER_FRAME, handler);
  }
  
  private function handler(e:Event):void
  {
   
   S.graphics.lineStyle(1,0xFFFFFF);
   var commands:Array = new Array();
   commandstring = commandstring.split(" ").join("");
   commands = commandstring.split(",");
   var i:int;

   for(i=0;i<commands.length;i++)
   {
    if(commands[i].charAt(0)=="m")
    {
     var dist:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     X = X + dist*Math.cos(Angle);
     Y = Y + dist*Math.sin(Angle);
     S.graphics.lineTo(X,Y);
    }
    else if(commands[i].charAt(0)=="l")
    {
     var changeleft:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     Angle -= Math.PI*changeleft/180;
     if(Angle<0) Angle += 2*Math.PI;
    }
    else if(commands[i].charAt(0)=="r")
    {
     var changeright:Number = Number(commands[i].split(" ").join("").split(":")[1]);
     Angle += Math.PI*changeright/180;
     if(Angle>Math.PI*2) Angle -= 2*Math.PI;
    }
   }
  

   //Resize to fit on the square after each iteration (purely aesthetic choice...)
   
   var Rect:Rectangle = S.getRect(S.parent);
   
   S.x += 275 - (Rect.x+Rect.width/2);
   S.y += 275 - (Rect.y+Rect.height/2);
   S.width = 550;
   S.height = 550;
  }
 }
}

Large Scale Stop Frame

In my spare time I study physics at the University of Birmingham. We're currently having some building work done on our main courtyard, so with access to one of the security cameras from our main clock tower (provided by an unnamed physicist) I decided to document the events. I wrote a program which is currently running on the physics mainframe, which essentially grabs an image from the security camera every 2 minutes during the day. I compiled these images into a video (with about 6000 frames so far) and you'll find the initial results in the vid below:



I plan on taking a few more weeks of images, the above is about 6 weeks. Enjoy.

For those of you who are interested here is the bash source code:

#!/bin/bash
#PBS -j oe
#PBS -l walltime=240:00:00

CLOSING_TIME=1
WEEKEND=0

cd /home/st-01/pictures

while [ 1 ]
do
#Determine the current time
hour=$(echo `date +%k`)

#If the current time is between 9am and 6pm not inclusive
if [ $hour -gt 9 ] && [ $hour -lt 18 ]; then
#Still taking photos - don't close up yet
CLOSING_TIME=0

#Retrieve image from the server and save it with a unique timestamp
wget http://YOURSITE.com/IMAGE.jpg
timestamp=$(echo `date +%y-%m-%d__%H:%M:%S`)
mv IMAGE.jpg ${timestamp}.jpg
else
#Otherwise must be the end of the day during the week
if [ "$CLOSING_TIME" == "0" ]; then

#ZIP UP THE IMAGES FOR THE DAY
date=$(echo `date +%y-%m-%d`)
zip ${date}.zip `ls *.jpg`
#Remove all non-zipped images
rm *.jpg
CLOSING_TIME=1
fi
fi
sleep 120
done