Generating pathfinding info from a mesh
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Posted 12 January 2005 - 12:49 AM
Members - Reputation: 122
Posted 12 January 2005 - 02:57 AM
By "throwing out" all the tiny areas and joining them with larger areas, you wind up with fews surfaces that you have to deal with. Then create a method of connecting these navmesh surfaces together (usually using the common edge between surfaces).
Don't forget that you can toss out any triangle or quad that isn't going to walkable. No need to include walls and ceiling polygons if your character can't walk on these surfaces.
Look at the Game Programming Gems books or the AI Game Programming Wisdom books for some tips on creating navigation meshes for you path finding.
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Posted 12 January 2005 - 02:59 AM
It's not perfect by any means, and not even optimal, but that was a while ago in an experimental project, and it works and is pretty easy to implement. It's basically a way to auto-generate a waypoint graph, and isn't a proper navigation mesh.
An alternative would be to loop through all the triangles and generate a graph by using the adjacent triangles as the connections, giving each triangle a max of 3 connections. Once again you'd probably skip unwalkable faces or faces that are too small.
One of these days when I get more time I plan on having a go at a proper navigation mesh pathfinder.
I'm developing FPS bots, and my current pathfinding implementation is waypoint system with some extra parameters such as waypoint radius that can be tweaked to provide loose or tight following between certain areas. Waypoint systems are so simple and still pretty decent representations they are still used in 95% of commercial fps games.
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Posted 12 January 2005 - 06:50 AM
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Posted 12 January 2005 - 08:32 AM
if you're new to pathfinding, I recommend using (manually) placed waypoints/nodes; this allows you to focus on pathfinding itself, rather than on generating a high quality terrain representation (a big enough problem in itself).
- read Paul Tozour's "Building a Near-Optimal Navigation Mesh" (ch 4.3 in AI Game Programming Wisdom)
- read Jan Paul van Waveren's MSc thesis "The Quake III Arena bot", p. 23-45
(available at http://www.kbs.twi.tudelft.nl/docs/MSc/2001/Waveren_Jean-Paul_van/thesis.pdf )
- buy Half-Life 2, install the SDK via Steam, select "Create a mod" and then inspect the source-code installed in your "mod" directory. It apparently contains the BSP parsing/mesh generation code by Mike Booth developed for his official Counter-Strike bots (as discussed at the 2004 GDC: http://www.gdconf.com/archives/2004/booth_michael.zip).
Mike's code is in src/dlls/nav*.*. Remember to first read Valve's license accompanying the SDK, and don't forget to play the game!
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Posted 17 January 2005 - 08:53 AM