Shang Liang » Maths&Physics

Box2D Tutorial

5566 — Mon, 02 Nov 2009 03:41:05 +0000

I gave a mini tutorial on Box2D during A-SFUG meeting. You can download it here. Have fun!

Box2D data visualization

5566 — Mon, 26 Oct 2009 06:11:40 +0000

Data visualization for join the pact campaign. Click to view.

Fun with Box2D

5566 — Thu, 15 Oct 2009 06:47:24 +0000

Messing around with Box2D. Quite fun.

Rhythm Surfer: Xtreme! An AIR Game (sort of)

5566 — Thu, 07 Aug 2008 04:53:40 +0000

This is my entry for Code::XtremeApps::2008. It was a 24 hours coding competition. Sadly, my entry didn’t even get pass the preliminary round. As usual, I conclude the judges didn’t know what they were doing and they are not good enough to judge my idea.

Download Here!

Using molecular mechanics in Flash

5566 — Tue, 15 May 2007 07:19:04 +0000

In actionscript.org george.sch posted a question about the effect used in coke5 site. The leaves get pushed away when mouse goes near to them and come back when mouse moves away.

The behavior reminds a lot what I learned in school last time. Molecules attract and repel each other at the same time. The attraction and repulsion becomes stronger when the distance decreases and the forces weaken when the distance increases. However, the rate of increase and decrease for repulsion is much greater than the attraction. So, when two molecules are close to each other, both the attraction and repulsion are strong but repulsion is stronger than the attraction. As a result, the system shows that the molecules repel each other. When the two molecules are far apart from each other, both the repulsion and attraction are weak but the attraction is stronger than repulsion, so the system shows that the molecules attract each other. If the two molecules are too far way from each other, both attraction and repulsion are very weak and the system shows no interaction.

The real equation can be found at this website in the non-bonded energy part. And there’s some interesting information at this page

To implement in Flash, the calculation for attraction force is modified. It’s a simple easing equation, of the molecule has a tendency to go back to it’s original position. And here’s the example in AS3.0. The source is >>here<< (both AS2.0 and AS3.0).

Shoot down a moving object

5566 — Mon, 04 Dec 2006 20:39:19 +0000

This is to respond to a forum post at http://actionscript.org/forums/showthread.php3?t=123006 posted by TOdorus. Quite good excerise for me. If my math teachers used Flash to teach me I think I wouldn’t hate them so much.

Click at the canon to shoot down the ship. It assumes the ship goes in straight line. If the ship turns back the bullet will miss it. I think it’s possible to expand the equation to handle all different movement, non-linear ones, as long as the ship moves according to a kown equation.

Read on to check the equations. >>source<<

Interesting Math Problem

5566 — Mon, 06 Nov 2006 07:09:54 +0000

There are n dots, p red ones and q blue ones. The target is to link up the red ones without having cross overs, e.g.

To produces this,

To solve this problem. I consider all the red dots lie originally on a perfect circle and this irregular pattern is produced by moving the dots further or closer to the center of the circle. So, I first calculated the center point of all dots, centerX=(x1+x2+…+xn)/n, centerY=(y1+y2+…+yn)/n. Using a center point, I calculate the angle of a dot as angle1=Math.atan2(y1-centerY, x1-centerX). All the dots are sorted by their angles and linked clockwise or counterclockwise.
Not something difficult but quite interesting .