Normal map seam for games

westsidazrhidaz

Hi guys I have a problem, i have 2 fps arms that uvs overlap each other, so both arm had the same texture so i decided to take a bunch of uvs and detach em and put em some place i had left on the map.(got that?) then i baked the textures so it has no seam at all, and it worked of course. But then when i bake the normal map texture(i put it in the diffuse slot) there is no seam on the texture but when i render there is. I really have problems understanding why uv seams is so hard on normal maps. heres some pics






thx for your help.

Hito

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...take a bunch of uvs and detach em and put em some place i had left on the map.(got that?)

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Nope. Can you be more specific?

from those two pics, it looks like part of the arm has normal baked on and part of the arm doesn't. Assuming that is the forearm in the picture.

from your description, it sounds to me like you've unwrapped the arms, overlapped their UV patches, then moved one arm's UV patch to another part of the UV map.

If you want both arms to share the same textures one arm has to be moved exactly 1 unit in the U or V axis. Otherwise it won't get the same texture.

westsidazrhidaz

first, thx for trying to help



ok those are forearm pads, and both share the same texture because both pads uvs are overlapped to get maximum space. it looks to symmetrical when you look at it, so i took a couple of polygons in the uvs, detached em and moved em somewhere i had place left over.so both pads uvs are still overlapping except for 4 polys that i detached(thats why i baked, so i get no seam). This way i can put some different textures on those 4 polys that are not overlapping to break the symmetry. The images i showed are the same map, one in diffuse slot, one in normal slot where it should be. its only to show theres no seam.


thx again.

MoP

i reckon it's probably just a bug with the way the renderer works (are you using Max or Maya, or what?)

have you tried viewing it in a game engine? my guess is it'll probably look ok...

Mongrelman

Perhaps the slight rotation of the patch is causing the error. Try only moving it down and baking again to see if that helps.

westsidazrhidaz

i just brought it into roboblitz, its very subtle without specular, but with it, you clearly see the seam. i tried without rotating the patch, same thing.

wow, im out of guess now, i tried straightening the uv borders too, i tried removing the padding in rtt, i tried putting 128.128.255 as background for antialiasing. and i gotta say, normal maps pwned me big time.pff i guess im gonna have to keep em all overlapped. if anyone has achieved what im trying to do, could you tell me how you did it plz.

thx for your help btw guys

edit:oh i forgot, heres an insane link http://discussion.autodesk.com/thread.jspa?threadID=547847 form alan noon.

Eric Chadwick

To fix the seams, the game renderer needs to import the vertex tangent data created by the normalmap baker, not just the mesh and map. The tangent info is needed to solve the lighting properly.

More info here.
http://wiki.cgsociety.org/index.php/Normal_Bump#UV_Coordinates

Joao Sapiro

Eric thanks for that read !

westsidazrhidaz

yea thx real interesting, though i regenerate the normal map with the changed uv so the tangent data is correct, and still in max i see a seam, maybe its the shaders, i know there was some problems with shaders and uv seams in max.

Eric Chadwick

Which shader are you using? Can't recall which Max shader works, but I do know the scanline renderer does use the tangents properly. I have heard Xnormal imports Max's tangents properly, you might try shading it in there instead of in Max.

westsidazrhidaz

I meant real time shaders, there was a know problem with max 7 and i dont know if it carried on to 9. but anyway, i generated the normal map from scratch again but this time i straightened the uv borders of the patch, and in scanline renderer it works great. Then i import in roboblitz and i can see the patch seam again. There is something i dont get with the vertex tangent data, it doesnt change the geometry proprieties, does it?

Eric Chadwick

Yes it does. At bake time the tangents are created and stored in the vertex data, similar to how UVs are stored. Make sure your exporter exports that data, Roboblitz imports that data, and the game uses that data to render.

Does UE3 include a normalmapper? I would think that would be the best way to avoid seams. IIRC the Doom III normalmapper worked well with that game, though you'd still get mirror seams along the midline.

Ged

I was also wondering about this, I imported my old fzero ship into roboblitz editor and it looks pretty cool with all the post effects and stuff, but the seams are slightly visible and definitely alot more visible than in max. An important thing I nearly missed was that when you import the normal map you have to change the filetype it exports with from tc_default to tc_normalmap. If you forget this and import as default the map does really strange things, bad lighting and seams etc

westsidazrhidaz

No i dont think robolitz got a normal map tool, and even though gears of war gets on the shelves tomorrow, im pretty sure its gonna be a level editor only, so, the sdk will probably get out with unreal tournament. But im starting to think if i could do 2 1k texture(instead of 1 2k map) and put each arm as a single object? do you guys think that would wok.

edit: oh and btw thx for that tip ged didnt know that, thx

Ged

oh its from jesse moodys site, follow this and if you still get horrible seams and lighting then I dont know whats wrong http://www.artbyjessemoody.com/ue3_tut1.html

westsidazrhidaz

Ive decided to place back the patch where it was so no seam there, then i followed his tut,regenerated the arms normal maps so the vertex data is correct and still have seams, anyway, maybe i need to wait for the sdk tools.




edit: Now that i think about it, i have the book character modeling by ballistic, and in there one of epic artists shows the workflow used for gears of war, he uses 3dsmax render to text and i dont remember seeing any seams in gears of war. So maybe its just me.

Eric Chadwick

It looks like Jesse is using the ASCII exporter in his tutorial, but I don't think that supports tangent data.

Rick Stirling

Quick thing - it's not a smoothing group issue, is it?

westsidazrhidaz

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It looks like Jesse is using the ASCII exporter in his tutorial, but I don't think that supports tangent data.

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yea he uses .ase files. so i guess i should wait for the sdk then, and its not the smoothing groups. thx guys, ill check what i can do and if i find a way ill let you know.

Sage

I think the ase export from max lets you save the normals, so you might have to turn that on.

Alex

MoP

While Max might be able to save the normal data to ASE, it's another matter of whether the editor will load that data. It's possible that the editor just ignores normal data assigned to the file.

FAT_CAP

There is a specular seam issue with some versions of the Unreal 3 editor - my guess is that is what you are seeing inside Roboblitz- not a seam from the normal map.

If the specular map is just a flat colour then there can be noticable seams on objects in certain lighting conditions - try breaking up the spec map with some noise as a test to see if this fixes the problem inside Roboblitz.

westsidazrhidaz

yea it is a flat color, it was only to get seam noticeable, im going to buy gears of war and try it in their editor instead. thx for the info guys

FAT_CAP

WEll if only a flat colour specular map shows the seam as noticeable then don't use a flat specular map?!?!!?