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Polygone size and phyisc issue

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Polygone size and phyisc issue

Postby Lamda » Sun Sep 27, 2015 11:16 am

Sometimes sad but never writen....

You need to choose polygone size of all driveable parts as small as must be all 4 wheels of the car on a different polygone. Otherwise you can get a "bump" effect, sinking tyre effect or falling throught mesh effect. The reason is allways same. RBR can´t sometimes equal physic of one polygone for two or more tyres. if you drive fast, the tyre have only time to sink a litte bit in to groundmesh so its only bump. if you drive slow and the polygone is not so big, the tyre will sinking till chassis get contact to groundmesh. if Polygone is big enough (and car slow), the car is sinking complete in to and will falling in the "blue"

I use a maximum of 2mx2m polygones for all driveable parts near road (aprox 10-15m besides the road. sometimes more if it is probable chance to lost control and sliding longer). so im sure it can´t happend for small cars too

Lamda
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Re: Polygone size and phyisc issue

Postby martinez » Mon Sep 28, 2015 10:51 am

Sure thing, thanks!
When afraid of FPS suffer because of dense mesh, you can leave ground mesh bigger and only tesselate/turbo smooth parts for collision mesh (or whatever technique you use to make polys smaller). This way maybe shadow generation can have easier job (but I can be wrong here as well - that is very challenging task to find right setting for shadows...)
I also observed that the more materials you use in .MAT, the bigger physic issues happen. So, for initial testing you may use bigger polys for ground mesh and use the same meshes to make .COL, then at the end - meshes for .COL must me more dense, while ground mesh stays the same. I believe that can help FPS a little.
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Re: Polygone size and phyisc issue

Postby Lamda » Tue Sep 29, 2015 7:16 am

When afraid of FPS suffer because of dense mesh, you can leave ground mesh bigger and only tesselate/turbo smooth parts for collision mesh (or whatever technique you use to make polys smaller)

the best way is to planing the right size during modeling first time :)

This way maybe shadow generation can have easier job (but I can be wrong here as well - that is very challenging task to find right setting for shadows...)
For shadows it is best you have square polypattern.

I also observed that the more materials you use in .MAT, the bigger physic issues happen.
Here i´m not with you. i use aprox 180 different materials and there are not any problem with physic (after fix the big poly issue)

So, for initial testing you may use bigger polys for ground mesh and use the same meshes to make .COL, then at the end - meshes for .COL must me more dense, while ground mesh stays the same. I believe that can help FPS a little.
it can help. but this make it more difficult for you to handle your data. In my opinion, we have 2015. hardware from 2010 shouldn´t get any problems with performance, if you not modelling wasteful. Remember, important is how many polygones show at the same time during driving (including car model if show)

Lamda
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Re: Polygone size and phyisc issue

Postby martinez » Fri Oct 02, 2015 10:04 am

I also observed that the more materials you use in .MAT, the bigger physic issues happen.
Here i´m not with you. i use aprox 180 different materials and there are not any problem with physic (after fix the big poly issue)

Of course - I was not too precisely - it was just an information. I mean - when I have just one material, I almost never have issues with big polygones - then when I add more - my car starts to bump and sink. It's maybe because the game has to "cut" textures and needs more/different calculations for changing from one physic to another. Never mind - you were right on all aspects, I just wanted to add something from me :)

By the way - on some original RBR stages the Ground Mesh (also on road) seems to be quite big too. Since I don't know of any methods how to check .COL file, I think they might do similar thing with more dense mesh for collisions.
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Re: Polygone size and phyisc issue

Postby Lamda » Wed Oct 07, 2015 7:16 am

I had issue on some terain parts (use one texture file and one physic), so more materials can´t be the reason. but maybe some combinations of materials generate problems....

if you made mesh with the "all 4 wheels must have a own polygone" rule, you got the sinking and bumping problem too?

generaly, it would be a solution to make col mesh only more precisly, maybe during one of the last steps because you have to handle both meshes in 3d.

Your releases havn´t such problems, i belive you will hold your very good quality :up:
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Re: Polygone size and phyisc issue

Postby martinez » Wed Oct 07, 2015 10:48 am

With enough dense mesh, I never have any problems. Obviously the road and close sides are more detailed even at beginning. Maybe on far ground there can be issues, but after a stage is finished, nobody drives there. And yes - I create .col mesh at very end of the process, so it is the final phase.
I make a copy of all of the ground meshes, stand invisible walls and hard colisions - trees, boxes etc. I merge the ground mesh into one object, since for .col generation it can be multimaterial. I always do that, so I'm 100% sure it is allowed. Then it's quite easy to tesselate the ground mesh to get sure that it will not cause any physic issues :)

And more - besides big final .col file, I believe the dense mesh doesn't harm the performance at all (FPS).
Only problems I had with Max/Panda exporter to process that amount of polygones - sometimes it did the work, sometimes didn't - the solution could be freeing up the computer's memory and restarting Max or even the PC.
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Re: Polygone size and phyisc issue

Postby Lamda » Thu Oct 08, 2015 7:18 am

I merge the ground mesh into one object, since for .col generation it can be multimaterial.

a new point for me, thanks. This make it more easy to handle it.

Only problems I had with Max/Panda exporter to process that amount of polygones - sometimes it did the work, sometimes didn't - the solution could be freeing up the computer's memory and restarting Max or even the PC.


yeah, memory is the key for 3Dsmax. i recommend min 8GB (better 16GB for bigger projects)

one tip beside, you have to close 3dsmax during importing meshes in Wallaby (Wallaby generate sometimes import error, but meshes are ok. it´s only a memory problem) . After optimised ground and general mesh in Wallaby you can use both beside.
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Re: Polygone size and phyisc issue

Postby martinez » Thu Oct 08, 2015 2:00 pm

I forgot to mention - .col meshes can be multimaterial and they also can be merged into one huge object :)
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