A few months ago, I posted on the separation of axis theorem. You can learn all about SAT and how it works here. What that post failed to do was use the SAT. We will explore using SAT for collision detection in this post. In the post on SAT, we created the code to detect collisions, however use of the code was not covered. (A download of all the classes used in the post is available at the bottom). The Shape...

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...

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...

Ray casting is a technique usually used in 3D worlds (often for rendering). Ray casting is exactly what it implies a ray is cast from a start point until it hits something (or a max length, so the computer doesn't die). Ray casting in 2D is great for collision detections, especially fast-moving objects (bullets). In this post, we will learn the basics of ray casting in 2D, then we will apply it to bullets in a...

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...

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...

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...