A* and Pathfollowing Steering Behavior
In the last three posts, we explored the how A* works, then we put A-star into code, then we looked at different heuristics for A*. Now we will combine A* pathfinding with the path following steering behavior. We have already done most of the work to do this. But we'll do a quick review in case you missed those posts. A* Pathfinding In A* we take a grid of cells and find a path from start to finish. Each...
Putting A* into Code
In yesterday's post on the basics of A star, we explored the theory behind A*. Today we will take that theory and put it into code. Because A-star uses a grid made up of cells, we need some classes to store that data. First the cell class: [as3] package com.rocketmandevelopment.grid.cells { import flash.display.Graphics; public class Cell { public var f:Number = 0; public var g:Number = 0; public var...
Separation of Axis Theorem (SAT) for Collision Detection
The Separation of Axis Theorem(SAT) is a technique to test whether two convex polygons are colliding. The SAT theorem: "given two convex shapes, there exists a line onto which their projections will be separate if and only if they are not intersecting." The line where the shapes have disjoint projections is called the separating axis. A separating line is the line that can be drawn between the two shapes,...
A* Heuristics
In the first post on A*, we explored the theory behind A*. Then we took A-star and put it into code. Now we will look at different heuristics for A* and how they affect the path. The Manhattan Method This is the heuristic function we used in our implementation of A*. The Manhattan method will get you to the end cell in the least steps, but it doesn't always guarantee the shortest path. It will usually give the...
Sierpinski Triangle
The Sierpinski Triangle is a famous fractal named after the mathematician who discovered it. It is made up of nested triangles that get smaller and smaller. If you were to zoom in, you would see the same image (though it may be translated) and you could zoom forever and never find the end. So, how do you create the Sierpinski Triangle in AS3? First you have to know how to do recursion. Recursion is...
Separation of Axis Theorem (SAT) for Collision Detection
The Separation of Axis Theorem(SAT) is a technique to test whether two convex polygons are colliding. The SAT theorem: "given two convex shapes, there exists a line onto which their projections will be separate if and only if they are not intersecting." The line where the shapes have disjoint projections is called the separating axis. A separating line is the line that can be drawn between the two shapes,...
Detecting Collisions with SAT
Today we will finally be detecting a collision with SAT. We know how SAT works, we've built classes to work with SAT, now we can use all of this to detect a real, live collision! Using the classes we created last time, this is quite simple. First create a shape: var shape1:Polygon = Polygon.rectangle(530, 30, new Vector2D(270, 360)); It's a simple polygon created using the static function of the rectangle...

Archive for June 11, 2010

Steering Behaviors: Seeking

Jun 11th

This entry is part of 9 in the series Steering Behaviors

Steering behaviors are used to create intelligent movements on a computer. These posts will be an AS3 version of the principles illustrated in Craig Reynolds’ article located at http://www.red3d.com/cwr/steer/gdc99/.

Before we can start using steering behaviors, we need a few classes. First we will be using, yet again, the Vector2D.as class. Steering behaviors rely on vector math, so you should be familiar with it.

If you need more information on vector mathematics, you can look here:

https://users.cs.jmu.edu/bernstdh/web/common/lectures/slides_vector-math-2d.php

http://en.wikipedia.org/wiki/Vector_%28mathematics%29

Next we will need a vehicle class to hold all the vehicle’s properties. The properties each vehicle will More >

2D, AS3, Math, Steering Behavior, SWF, Vector

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- Using Ray Casting with Shapes February 16, 2011
- Detecting Collisions with SAT November 29, 2010
- Using the Separation of Axis Theorem November 23, 2010
- Steering Behaviors and A* Source November 15, 2010
- A* and Pathfollowing Steering Behavior November 10, 2010

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