I have a wrap around world (only in X direction) and I intend to use steering behviours to control AI units so that they seek and arrive at the player. Now this in theory works fine except when the player crosses the wrap-around barrier. For example if the player is in a world that is 0 - 100 and crosses the 0 barrier the AI units immediately switch direction because the player is now at somewhere near 100. This would be fine if the camera were static and the whole world was in the view frustum but in my case the camera chases the player so you get AI units that suddently veer away from the player for no apparent reason (the wrap-around points are not obvious to the player). I have thought of two of solutions to this, both of which introduce complexity: 1, Keep track of what the AI unit is chasing and if the distance suddenly increases by a huge amount (target crossed the barrier for example) then compensate for the barrier crossing. 2, Transform the AI and the target into a common screen space rather than world space whenever seeking and arriving is in operation. They will be in relation to each other at all points then. Anybody have any other ideas?

Once your world wraps around, you no longer have a unique system of coordinates. (50, 50) is the same as (50, 150) and (50, -50), if you see what I mean. I think I might try the tack of considering several of the many coordinates of my target in the tracking AI, and going after whichever is the closest point. I'm sure you could do it and only need to consider two or three possible coordinates.

This is the same as your #2 and the solution posted immediately above this post, but it maintains a kind of mathematical consistency that I like.

Example along one axis: AI is at 90 and target is at 99. This is the same as AI at -10 and target at -1. Anwyway, when the target moves up to 105 (5 after wrapping), now the AI is at 90 and the target is at 5 (or 105). 105 is closer... go for that! After all, 105 and 5 are equivalent. This is your #2 exactly, with an extremely convenient common coordinate space.

Yeah, well, there's many ways to do this.

The previously suggested solutions are simple and do function, but I would like to make an addition. I find my way to be very similar in many ways, but even simpler.

Perform all pathfinding calculations in an artificial coordinate system; not the real one. In this coordinate system, the agents position is coordinate 0:0. Every other coordinate - such as the players - is mapped into this system, relative the agent. Everything is relative the agent.
The edges of this coordinate system is the opposite side of the world. When you have all coordinates inside this new space, you'll have a very easy time calculating whatever you want. Such as the shortest path, or the direction to wherever.

This is the way I would personally do it. It's easily implemented, without any fancy mathematics, and it does not hinder you from adding additional functionality later. A simple, functioning and expandable solution, right from the start.
Good luck!

Nice - I like that idea.

The solution proposed is similar to #2 that I had originaly proposed.

In some ways TimKin I am already handling it your way since the world I am performing this in is already segmented horizontaly into segments.

They jury is still out on which method I am going to use and I may try out all of the suggestions here. I am not too concerned with the amount of processing requirements as this really isn't going to be the bottleneck. But I live by the mantra 'the simplest way'

... I had a reply here, but I noticed there's something wrong with my math, so I removed it until I've figured it out...

[edit:]

At the time I really did believe my way was much simpler, but you're right - I shouldn't say so anyway.

I figured out what my math error was now. Turns out I was underestimating how many lines of code was necessary to translate the coordinates... =) You need 2 rows (including 2 if-statements), but I thought you needed a whole lot less.

I don't like to discover that I miscalculated, so I've sort of obsessed over this riddle for the last 45 minutes... heheh... I find it funny now as I go back over the thread, and see OP start the thread with a good solution (#2) and then Palidine, rileyriley and myself all reinvent 3 mutated clones of the same solution.
Actually, Timkin is the only one who posts a different solution, and funnily - that's the one solution which doesn't work... :D

[Edited by - NQ on April 26, 2006 8:34:18 AM]