Path straightening after A* with apex and tunneling

[pcwlai]

I have my A* path finding engine working properly. Now, I face the problem on path straightening. There seems to have little discussion in the game development forums and I cannot find much information from google or so. Hope to find some light here.

My A* uses triangle meshes as the search space. I get information on the neighbours but not visibilities because of the large amount of triangles.

After searching for some time, I discovered some artivles using the tunnel and apex method in path straightening. Though, I just get the brief description. Where can I find more in depth descriptions?

The other problem is, the descriptinos say it can only use for fixed starting point problems. So, is that true?

Is there any other fast method in straightening paths after A* on the trignale meshes?

[Scramasax]

Could you define path straightening for me? Optimizing the nav mesh?
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[chot]

You might find this article usefull: http://www.gamasutra.com/features/20010314/pinter_01.htm

[GroundKeeper]

It might also be useful to have multi-layer path network grids. In practice a friend of mine implemented a multi-layer search grid for a project to optimize speed but the fact that each layer could convey a larger pattern the path was actually very nicely smoothen by the transisions downwards in layers.