Visual artifact with intersecting meshes.

RyanRay · Post by **RyanRay** » Wed Jun 28, 2006 3:11 pm

Apologies if this has been answered before, I've tried searching and the wiki seems to be down. Feel free to lock/nuke and PM me with the relevant info, if there is any.

I've been looking at switching to Irrlicht for various reasons, and in the process off assembling a toolset and running through a few tests I've come across a problem, specifically to do with intersecting meshes.

I've attached a picture of a simple scene with 2 intersecting meshes which when used in Irrlicht produces the jagged artifact.

I've tried various scenes and various file formats, but they all produce the same result. I'm guessing it has something to do with the depth buffer, but all I really want to know is, can it be fixed or avoided?

Cheers very much.

TheGameMaker · Post by **TheGameMaker** » Wed Jun 28, 2006 5:51 pm

mhh. maybe you scaled your mesh very small/big...
you can easily avoid it by don´t let tris intersect!

Amt0571 · Post by **Amt0571** » Wed Jun 28, 2006 6:31 pm

It happened to me with a nVidia Geforce 4 MX card on my university. At home, I tried with an MX 440 (but with newest drivers), a Radeon 8500 and a 6600GT (also with newest drivers) and the problem is not there, so I'll think it's a driver related problem.

mullencm · Post by **mullencm** » Wed Jun 28, 2006 8:18 pm

I have seen this before in other sdks when I use 16bit window depth vs 32bit which in turn affected the z-buffer i think.

mullencm · Post by **mullencm** » Wed Jun 28, 2006 8:22 pm

I have seen this before in other sdks when I use 16bit window depth vs 32bit which in turn affected the z-buffer i think.

hybrid · Post by **hybrid** » Wed Jun 28, 2006 9:10 pm

Yes, this seems like zbuffer fighting due to loss of precision in 16bit. 32bit is better anyway, but you can also change the view frustrum to reduce zbuffer depth.

RyanRay · Post by **RyanRay** » Thu Jun 29, 2006 10:19 am

Thank you for all your help.

It's not a driver problem near as I can tell, as I'm up to date on all 4 computers that I tested on.

I'm also using 32bit, so I don't think the problem is there, though I won't discount this untill I know more about Irrlicht.

I think I'll just use .bsp maps for my levels, as the problem doesn't occur with them (obviously), and come back to the issue at a later date.

Cheers again.

hybrid · Post by **hybrid** » Thu Jun 29, 2006 12:37 pm

There's also a pacth from IrrSpintz which is related to gfxcard FPU setting. It can happen that the FPU settings are left untouched, i.e. are using 16bit precision even for 32bit devices. Maybe it's something like that (I did not try the patch, yet, as I'm usually not using windows, and it's only happening with D3D).

mullencm · Post by **mullencm** » Thu Jun 29, 2006 9:48 pm

I made the same just happen with dx9, then with opengl and the problem is gone.

RyanRay · Post by **RyanRay** » Mon Jul 03, 2006 12:30 pm

I'm quite happy as I've solved the problem. For those who care, it was a problem with the far clip plane. By default it's set to 2000. Bumping this up to about 15000 seems to get rid of the problem completely.

I solved this by accident, as I was messing around with clip planes in Light Map Maker and reproduced the similar artifact.

Thanks for your help anyway

Mutter · Post by **Mutter** » Tue Jul 11, 2006 7:07 pm

I had exactly the same problem...

solved it:

i had to keep attention to the ORDER i create my objects!!!!

for example...these 2 walls with the ugly thing are created BEFORE the other walls and floors on the screen...

create the two top walls AFTER the floor and things...

this solved similar situation at my project

Irrlicht Engine

Visual artifact with intersecting meshes.

Visual artifact with intersecting meshes.

another solve for this problem!!!