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Aimesh, col3 and bots
Dnamro
post Feb 2 2008, 04:33 PM
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Since this thread got off on explaining Col3 meshes, I split it off.


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DEVILMAN1
post Feb 6 2008, 04:32 PM
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What is or what are col3's
In simple English please
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Dnamro
post Feb 6 2008, 04:47 PM
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col3, short for collision 3 meshes, are also called AI meshes. When creating the bot paths (navmeshes) the editor will use the col3 mesh (if it exists) to create the bot path in place of each object. Without one, the editor assumes that the bots don't need to use that object and creates a path that does not include that object. You don't need col3 meshes for stuff like rocks, trees, fences and anything else that want the bots to avoid, but its really good for buildings and bridges.



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DEVILMAN1
post Feb 6 2008, 05:06 PM
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QUOTE(Dnamro @ Feb 7 2008, 06:47 AM) *
col3, short for collision 3 meshes, are also called AI meshes. When creating the bot paths (navmeshes) the editor will use the col3 mesh (if it exists) to create the bot path in place of each object. Without one, the editor assumes that the bots don't need to use that object and creates a path that does not include that object. You don't need col3 meshes for stuff like rocks, trees, fences and anything else that want the bots to avoid, but its really good for buildings and bridges.

Thankyou for you "simple" answer
So when you place an object in a map with the editor,if that static/building/thing has a col3,it will automatically create an area around itself,like an exclusion zone that bots cant and wont crossover or enter into
Also why dont rocks need a col3 ???
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red.murder1
post Feb 6 2008, 05:16 PM
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rocks don't need a col3 because you want bots to aoid them anyways


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imtheheadhunter
post Feb 6 2008, 06:49 PM
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QUOTE(Dnamro @ Feb 6 2008, 05:47 PM) *
You don't need col3 meshes for stuff like......trees


correction, you DO want a col3 mesh for trees. otherwise you get a really big hole in the mesh, which can really screw up the mesh. especially when the tree is over something important, like a CP, a few spawn points, etc.


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Dnamro
post Feb 6 2008, 07:41 PM
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IMTH, brings up a good point. The editor clears a wide area around the object if it does not have a col3 mesh. So, its good to have a col3 for every object so it will only clear the path that the object covers, but most of the time its not going to matter if the bots have to go a little further to get around an object.


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kysterama
post Feb 6 2008, 07:49 PM
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The simplest way to explain it is, that you want a col3 on any static that you want a bot to walk on or in. A tree doesn't need a col3 because its current collision meshes will make sure the trunk will have a gap around it. The navmesh leaves holes based on the objects current collision mesh (Which is usually a closely fitting yet highly optimised version of the visible mesh.)

Hence, if a large square building has no col3, it will leave a large square hole in the navmesh. If it has a planned out col3, then the navmesh will make pathways inside the building, up stairs, on the roof etc depending on the layout of the building and the complexity of the col3 in relation to the layout of the visible mesh.

The actual gap between the surrounding navmesh and where a tree, rock or building is located, is defined in the navmesh radius settings and can be set to cut closer or furthur away from the object (The vehicle mesh has a much wider radius than the infantry for example.) The current set of col's are more than good enough to cut the hole out of the navmesh for a tree. On the other hand, if you had a big hollow tree with a spiral staircase or ramps inside it going up to a treehouse, then it would definitely need a col3 that conforms exactly to those ramps and platforms, otherwise it would just cut a big hole out of the navmesh a little bigger than the size of the trunk with no internal pathways for bots.

Rocks don't have col3's but those of you who have done navmeshing will see that if a rock is sunk into the ground far enough and the side of it doesn't exceed a 45 degree angle, then the navmesher often overlaps the navmesh up the side and on top of the rock. Purely because there is a navigatable path onto the rock. Same with sandbag walls on occassion. In short if there is no col3 (AI mesh) the navmesher will use the next best Col. The next best col often doesn't have the internal of a building mapped out which is why it punches a big fat square (a little bigger than the buildings circumference) into the navmesh instead. This is pure speculation of course based on observations, heh. I could be wrong tongue.gif

One thing that leads me to the theory is that if you look at an objects col meshes in the editor, for statics you know don't have a col3...the AI mesh is usually identical to the physics mesh meaning its just defaulting to that one if a col3 is not present.


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imtheheadhunter
post Feb 6 2008, 08:23 PM
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QUOTE(kysterama @ Feb 6 2008, 08:49 PM) *
otherwise it would just cut a big hole out of the navmesh a little bigger than the size of the trunk


in my experience with trees that dont have col3 meshes, the hole that is put in the mesh is MUCH bigger than the trunk. its about as big as the entire spread of the leaves. if the leaves cover an area of 30m wide, then the hole is going to be just over 30m. definatily way too big to make a decently useful mesh with. at least when you have that tree near anything important, like a CP, spawn points, roads, etc.


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Dnamro
post Feb 6 2008, 08:31 PM
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I have had the same experience as IMTH that any object without a col3 creates a hole in the navmesh that is much larger then the object. Sometimes this can cause problems when you have these objects close together and the holes don't allow a path through them. In that case I just replace the object with a similar sized one that has an AImesh and regenerate the navmesh.


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kysterama
post Feb 6 2008, 09:56 PM
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Weird, I've never had that problem before. Are these with custom overgrowth meshes? Because Dice physics meshes are pretty good at conforming to the shape of the visible mesh.


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SatNav
post Feb 6 2008, 10:16 PM
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QUOTE(Dnamro @ Feb 7 2008, 11:47 AM) *
You don't need col3 meshes for stuff like rocks, trees, fences and anything else that want the bots to avoid, but its really good for buildings and bridges.

QUOTE(kysterama @ Feb 7 2008, 02:49 PM) *
Rocks don't have col3's but those of you who have done navmeshing will see that if a rock is sunk into the ground far enough and the side of it doesn't exceed a 45 degree angle, then the navmesher often overlaps the navmesh up the side and on top of the rock. Purely because there is a navigatable path onto the rock. Same with sandbag walls on occassion.


all those objects have col3's, you can see them in the editor when switching between the different col's. alot of the simpler objects dice has reused used the physics col for the col3. if a col3 is not there then when you switch between the soldier col and AI col the col3 will be the same as the soldier col because that is the next col down in the hierarchy of the object.


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imtheheadhunter
post Feb 6 2008, 10:23 PM
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QUOTE(kysterama @ Feb 6 2008, 10:56 PM) *
Are these with custom overgrowth meshes?


their the custom trees from EOD2(see maps, Solomon showdown, Bataan, and husky.) i dont think the trees in husky got replaced, so you should still see the huge holes in the mesh that they made. for the fun of it, try to gen a mesh for Solomon showdown with those trees left in it. the mesh ends up looking like a shredded piece of swiss cheese. drool.gif


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SatNav
post Feb 6 2008, 10:26 PM
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theres a sticky thread where Outsider explains about col3's. http://battlefieldsingleplayer.planetbattl...585&hl=col3
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kysterama
post Feb 6 2008, 10:48 PM
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Righto, so basically if there is no col3, the navmesher doesn't actually use any of the other col's, it just uses an imaginary box that encompasses the whole mesh. I was confused by the editor displaying col3's when you turn on the AI mesh for statics I know have no col3. (eg, the carrier wasp in the xpack and also the submarine pen in the xpack.) Both caused huge holes in the navmesh, but if you turn on the cols in the editor the AI mesh looks perfectly fine.

So to sum up, if a mesh has no col3 in the editor, it will simply show the col2 in its place.
BUT the navmesher does not use the next col in line (col2) it will just default to an imaginary large bounding box that encompasses the entire mesh. Sorry for the confusion and my meandering musings, heh.

Wish we could import collision meshes into max to have a good look. sad.gif


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