Game Development Community

T3D mesh hiding: multi-mesh model lightning errors

by Peter Pedersen · in Artist Corner · 04/08/2010 (10:53 am) · 37 replies

I'm currently working on some character models with multiple meshes for use with mesh hiding.

My problem is that strange shadows appear where the models are split. I reproduced the error on a simple cylinder with straight faces:

www.wandering-willow.com/forwebforums/GG/Testcylinder.jpg
textured and normal mapped, normal mapped no texture
(the log on the ground is a single mesh for comparison.)

The vertexes share the exact same coordinates, the normals are facing the same way.
I searched the forums on the topic, but haven't found a solution yet.
It seems like the problems that occur with normal map seams and calculating the lightning, which was the only similar topic i could find.

I was wondering if I was the only one who ran into this problem with multi mesh models, or if anyone has come up with a solution for it-

Thank you
Peter

About the author

Started out on pixelpushing on the Commodore 64 and Amiga since '87 Worked with 3D modelling since 2001 so now I'm just a "fluid, lightning-fast, no hassle work flow, effortless art guy"

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#21
04/22/2010 (1:14 pm)
Horray!!

It's working now!
With the smoothgroups on and the normals welded and the right exporter it is possible to have 2 separate meshes showing up as a single "surface" without any seams showing!
The balls on the left are the same as in my previous picture, now without the shadow showing.

www.wandering-willow.com/Forwebforums/GG/WorkingNormals.jpg
The logs are the same as in the first post, 2 separate meshes now showing up as one, and it's rounded too. In the top I kept different smoothing groups, to show the transition from smooth to "edgy"
Thanks for your help guys! This is really making things easier in regards to our mesh hiding situation!
#22
04/22/2010 (3:39 pm)
told ya I'd get ya there! :P
#23
04/24/2010 (10:06 pm)
Yea!......you did it, Peter. Keep on Deving...and don't give up; it is the way to get things sorted.

Rex
#24
07/07/2010 (2:31 pm)
THE SINFUL FLESH!

Since the last post here I have been busy planning and finishing all the meshes and unwrapping for my player.

But when I use the new "normal exporter" on my character it crashes max!

I read somewhere there could be trouble with normals and the skin modifier.

I unwrapped all the editable meshes, welded the normals at seam edges, applied the skin modifier, and set up detail level and usual stuff for export.

I did a test - simply exported it in "the old"/standard dts exporter and it went trough like a peach.

I compared the logs and found that
the new crashes MAX before it enters "generating faces..." in the log (for the first mesh):

-bla bla bla-
...
Adding object named "LegTrousersDestroyed".
Adding mesh of size 5 to object "LegTrousersDestroyed".
//here the "new" crashes max
--the old starts treating the first mesh//
Generating faces for skin "LegTrousersDestroyed5".
88 faces, 264 verts, 264 tverts before cropping textures and joining verts
-bla bla bla-

the old exporter ecompletes all 56 meshes and the dts imports correct in T3D (except the normals are bad)

Have you any idea what may cause this, and do you know any steps that may solve it?
I tried cutting the skin modifier, and then the meshes export fine with ok normals, so it must have to do with the "fleshy" part...

#25
07/07/2010 (3:15 pm)
what is the "LegTrousersDestroyed's" poly count ?
#26
07/08/2010 (9:46 am)
in 3d max it says 53 Verts 88 faces for that mesh

In the log it says 264 vers before joining verts
71 verts after joining

-By polys, do yo mean the 88 faces?

I can only see a total polycount of all the meshes in showtool, which is 9723


#27
07/08/2010 (5:11 pm)
How does your mesh have 88 faces, but only 53 verts?
#28
07/08/2010 (10:24 pm)
I do not know, but do you think this is why the new exporter fails where the old one keeps on going?

I tried deleting the meshes one by one and re-exporting but it still crashes.
#29
07/09/2010 (8:35 am)
the mesh:
www.wandering-willow.com/Forwebforums/GG/Legtrousersdestroyed.jpg
It is open faced on one side, it has 7 verts in the middle,22 polys to

the left and mirrored on the x axis, that is 44 tris to the left and 44

tris to the right when converted to mesh, totalling 88 faces and 53

vertices... - do you think it's important I have an uneven number of

verts?
#30
07/09/2010 (10:01 am)
heh, no. Verts and poly counts can vary and should not cause concern unless your geometry is a considerable mess...which this is clearly not.

- are there any other meshes with open sides or open edges ?
- have you tried deleting this specific object from the model and then attempt exporting ?
- are all objects editable meshes ?
- is anything else in the model mirror'd ?
#31
07/09/2010 (2:47 pm)
since the model exports fine with skin modifier on in the standard dts exporter, and animates in T3D I assume the model is fairly ok.

Yes, all the meshes in the model have open sides and edges.
Yes, as I tried to explain, i started out deleting the meshes causing problems, and I ended up deleting half of my meshes before figured something else must be wrong.
I deleted the skin modifier and all the meshes exported correctly and I was able to import it in T3D.
-Yes all the meshes are editable meshes, otherwise they won't export, and the stack is collapsed before the skin modifier is applied. I tried exporting another model with bones and a skin modifier, and all the meshes with normals aligned to eachother caused errors and stopped the export dead.

It's a tough nut, and I really am grateful of your help guys!
#32
07/09/2010 (3:36 pm)
Then all I can suggest is that you export as collada to get the specified normals use through DAE 2 DTS conversion to DTS version26.

Sorry I can't help you more on this Peter.
#33
07/09/2010 (10:28 pm)
Well, thanks for trying anyway eb!
I'll post it if I get it to work.
Still have some hair left to pull, so I'll give it a go before surrendering to DAE :-)
#34
07/13/2010 (4:17 am)
Only managed to pull half of it, the opencollada worked better than autodesk collada. And managed to find DAE2DTS in my T3D download menu.

(I have not yet figured out why an audio dll manages to keep directx from working when handling graphics convertion, but got that important one updated too!)

The normals are working now, and the animation is running, just have to touch up those normal maps, and we're back on track!

Thanks for lighting up the way eb!
#35
07/22/2010 (8:49 pm)
Speaking of lighting up the way... when I move the camera past a model exported like above (to collada and converted to dts) tiny cracks and pixels show up. -Like back in the TGEA days with constructor.
Since the surface normals are aligned and converted via Collada could it be an engine bug that causes these edge/light artefacts on skinned meshes?
I admit I try pushing the limits, but it should work...
#36
07/22/2010 (11:44 pm)
can you post pics of a few angles of the issue ?
#37
08/03/2010 (7:36 am)
Going over my model with the great zoom lens I found that 2 of my meshes were 0,001 off of the center axis which led to these specks of light! :-(

I should have checked this before working myself up to a frenzy, sorry!

Now we only have to get the model to touch the ground again and face the right way. Digging into collada importer documentation...
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