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AppGameKit Classic Chat / Free Code - Automatic waypoint system for use with AI systems

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baxslash
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Posted: 4th Oct 2011 18:06 Edited at: 3rd Nov 2011 23:12
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This is a system I'm working on for a game but I thought I'd share it.

Latest Version!

It is not finished but is nearly there so I thought I'd share it and get some feedback. I just have to do a reverse search which will find a quicker route in some circumstances.

What does it do?
It allows you to create a set of waypoints either automatically or by inserting waypoints where you need them. Then you can use the "find_path" function to find the fastest route between any two points.

The fastest route is stored in an array which you can then read to get the route for your characters.

Currently the search takes less than 2ms on my machine so I'm thinking lag will be minimal.

Commands
init_waypoints:
This initialises some global variables. Some code still needs to be moved in here...

create_rect_obstacle(x#,y#,width#,height#,angle#)
Adds a rectangular obstacle (currently all obstacles are visible but I'll be adding a method to hide / show debug images later) and all the necessary waypoints needed to get around it from any angle

create_obstacle(x#,y#)
is a 'random' rectangle creator and the predecessor of the previous command, used for testing

add_waypoint(x#,y#)
Manually adds a waypoint into the system

calculate_waypoint_nodes()
Works out the closest 8 waypoints to every other waypoint and stores it (and the distance to it) as a 'node'. This data is used to calculate fastest routes later. Also any waypoints that clash with other scenery objects are deleted.

show_waypoints() / hide_waypoints()
This will be hidden in the debug code later

find_path(x1#,y1#,x2#,y2#)
This is the command used to calculate the fastest route between two points


If you plan on manually adding scenery it should be in physics group '2'...

Attached is the full code and a working test project.

I will be updating this source code as it improves.

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Red Eye
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Posted: 4th Oct 2011 18:21
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Awesome!
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baxslash
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Posted: 4th Oct 2011 18:31
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Thanks @Red Eye

My advice is don't use it... yet.

It will be much more flexible / accurate and usable soon.

I tried it on 20 marines in my game and there was no noticeable lag, they just all set off on their own various routes to the rendevouz without pausing (except to shoot the odd zombie)...

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Red Eye
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Posted: 4th Oct 2011 18:37
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I tried the demo you included, and it works great.

I was thinking about making a platform AI bot. And use the same "make_obstacle" module. This means it would jump to the nearest obstacle (relative to you) if distance is close enough.
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baxslash
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Posted: 4th Oct 2011 18:45
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Quote: "I was thinking about making a platform AI bot. And use the same "make_obstacle" module. This means it would jump to the nearest obstacle (relative to you) if distance is close enough."

I hadn't considered using it for platforms, I have a feeling it would struggle for side scrolling games but I guess it could be adapted.

I made it for top down games really. I'm just tweaking the main path finding algorithm now to do an extra run to find a possible faster route, this is only necessary because the way the waypoints choose their nodes is not bi-directional so sometimes a faster route is missed looking from start to finish. My second run looks from finish to start and compares the minimum distance before deciding which route is best!

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BraindeaD
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Posted: 4th Oct 2011 19:08
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Thanks for sharing, baxslash.
maybe it will useful for me in my tanks game when cpu tanks are chasing the player. I'll follow this post to see the new versions.

Regards
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baxslash
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Posted: 4th Oct 2011 19:28
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Hi BraindeaD, I hope it will be useful! I'll be posting a new version over the next few days.

Tank games could certainly benefit from this kind of system.

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Scotty1973
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Posted: 4th Oct 2011 19:48
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Looks great!!! Can't wait to see the new version!

Scotty
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baxslash
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Posted: 4th Oct 2011 20:13
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Hey scotty! Burton on Trent! I'm in derby

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Cliff Mellangard 3DEGS
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Posted: 4th Oct 2011 20:35
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Nice work !

Maybe we should start putting all the good agk code snippets in the snippets board soon ?

The others simply write dbp or db for wath version of dark basic they use.
Why shouldt we simply write agk in front of our snippets in the same thread?
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baxslash
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Posted: 4th Oct 2011 21:00
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I don't see why not, this isn't quite ready yet though...

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bjadams
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Posted: 4th Oct 2011 21:58
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idea: option to move in a bezier curve and not straight lines
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baxslash
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Posted: 4th Oct 2011 22:07
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I'm sure that with a little extra work you could create a set of bezier curves from the positions of the sprites returned by the function. I don't really need it for my own game.

This code is a step or three along the road for any game that needs a pathfinding solution, nothing more.

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Hodgey
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Posted: 5th Oct 2011 02:08 Edited at: 5th Oct 2011 13:58
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This is spectacular baxslash! Excellent work! Now all I've got to do is go through it in depth to see how you did it.

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baxslash
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Posted: 5th Oct 2011 11:56 Edited at: 5th Oct 2011 11:57
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Thanks Hodgey! It's based on Dijkstra's Algorithm more or less but I kind of came up with my own way of doing it because I didn't really 'get' the code I found for the algorithm...

The pathfinding works like this:
Each waypoint has 'nodes' which are links to other waypoints. It stores the other waypoint's sprite number and the distance to it. Starting at the nearest waypoint to the start it loops through all the other waypoints that are attached to the first waypoint and finds the shortest distance to each of them (storing it in the waypoint array). Then it starts at the nearest waypoint to the target point and works back through the waypoints to via the shortest route (smallest stored value visible from each waypoint) until it reaches the start again.

There's a bit of optimisation after that but that's basically it!

There's also a bunch of code for automatically adding the waypoints and working out the nodes for each waypoint.

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Hodgey
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Posted: 5th Oct 2011 14:14
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Ok, I think I understand. So if I had moving objects, I would need to call the find_path function each loop wouldn't I. I see this working out quite nicely baxslash, thanks for sharing!

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baxslash
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Posted: 5th Oct 2011 14:19
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Quote: "So if I had moving objects, I would need to call the find_path function each loop wouldn't I"

No you could do what I am which is to store a set of waypoints in the character's array and then as he reaches a waypoint tell him to go to the next one, something like (psuedo code):


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baxslash
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Posted: 3rd Nov 2011 23:09
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This code is not quite 100% yet but it works in most cases. I'm posting the current version here as now I'm going to put it in my game. If I make any further adjustments I'll try to re-integrate them into this version and post it here (attached)!

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