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Normal Mapping problems

ZBrush Usage Questions
#1

Hello everyone,

I am working on a model right now, and I’m having some issues with the normal maps. I wasn’t sure if anyone here has encountered this problem before, but I was hoping someone may be able to help me out.

What I have is a model I created in 3ds max 2009; the character is symetrical with mirrored UV coordinates. I have all the textures applied (diffuse, spec and normal) and when I place one light in the scene everything looks great. But when I turn another light on in the scene from the opposite direction I get a nasty seam in the normal map. This wouldn’t be a problem if I was doing a simple image as I’d just render out seperate lighting and composite it in post, but this is a real-time character and when I import it into the Unreal engine I see that nasty steam.

I’ve tried everything I can think of to fix it; removing the alpha channel from the normal map, smudging the edges out and nothing seems to help at all. I even went so far as to draw a white dot on the normal map texture and render it out in max to see what it does, and it seems that it’s rendering one side as ‘white’ and the other as ‘black’.

Does anyone have any idea as to what is causing this problem…or more importantly how I can fix it. I have been doing this for a while and never encountered this problem before.

I’ve included some pictures to show what exactly is going on.

Thanks in advance,
Jamie

The model with 2 lights
http://m3tz.wc3server.com/help/2.jpg
The model with 1 light
http://m3tz.wc3server.com/help/3.jpg
The model in Ued
http://m3tz.wc3server.com/help/4.jpg
The dots
http://m3tz.wc3server.com/help/5.jpg

#2

can we see the uvs? if u have overlapping uvs then that’s bad, if not u can try redoing the uvs to try and hide the seams

#3

http://m3tz.wc3server.com/help/6.jpg

yeah, they are overlapped UVs. (basically the model was split in half, then mirrored and the seam was welded)

#4

Did you inverted the normals of the faces??

#5

Nope, didn’t do that. I even tried going into max (just now) and flipping them (and unifying them too) but that didn’t fix it.

#6

Fliping them for render time…

#7

are you sure you made a Tangent Space normal map?

#8

Yep, I double checked that I made a tangent space normal map.

I’ve tried flipping the normals and whatnot but all that does is turn that part of the mesh inside out come render time :confused:

EDIT
I just went through and played with the settings of the normal map (in max) changing it to local, screen, and world just to see what would happen. When I change it to local the seam disapears, however, all the other seams appear and the model looks all wacky.

I thought that was kinda wierd so I thought I’d better share the results in case it helps.

#9

i’m actually surprised ZBrush didn’t crash when creating a normal map for a model with overlapping UVs. this isn’t supported, and i would understand why you would get seams on layered UVs with a tangent map. you’re not going to get good results with any app like that… yes with diffuse maps and such, but not tangent space normal maps.

#10

I decided to just go through and redo the UV maps…

One cool thing though is I can use zBrush to project the old texture maps. Just import the model, subdivide (I can get to 24million polys on this computer but ran into a problem projecting so I will have to play with some settings). Import the texture, click the TXT>COL button to project the texture to polypaint. Then import the new UV mapped model and subdivide to the same level and add it as a subtool. Click PROJECT ALL and export the texture after clicking the COL>TXT button.

Man I love this program.