Normal Map Black Edges

ChrisCorr

Hey there,

This must be the millionth thread on this normal map business but I couldn't find anything related to my specific problem.

I think I've done everything right, but still I get some black edges with my normal map.

https://www.dropbox.com/s/gz6tj89eyrhgaox/BlackEdgeHelp.jpg

On the left you can see the UVed model, the green edges are UV Splits. You can also see the corresponding section of the UVmap. On the right you can see the 3D models, the orange highlighted edges are where I put hard edges. And below you can see the normal map I baked and applied.

Even though I made the edges hard where I split my UV's, these edges have the black artifact.

There are just a few of these on the rest of the model, most of the edges are perfect and they are set up the exact same way with hard edges only on UV splits. Basically I made every UVSplit a hard edge, and yet only a few of these present a black edge problem.

Can someone please help me understand?

Obscura

Hi

This is how it should look like with a this low geometry. Add simple chamfers to avoid this.

Some notes:
1. The black edges won't be this visible, once you texture the model.
2. The black edges won't be this visible in motion in a gameplay.
3. Depending on the object's size, The black edges shouldn't be visible from a reasonable distance. If the object will be a big object, so the black edges would be visible from further too, then you should obviously add chamfers if those black edges are disturb you.
4. You can reduce the wideness of the black edges with sharpening the edges on the highpoly but its not recommended, use chamfers on the lp instead, or simply ignore the "issue".

5. You almost never meet with black ambient color in games or in engine scenes, so those edges wouldn't be black.

ChrisCorr

Thanks for your reply.

So I shouldn't worry about this small stuff because it won't be visible anyway? It's hard for me to just ignore these imperfections but I suppose if nobody will notice them I shouldn't care.

Obscura

Hmm. Wait. Sorry, first I thoungt you are talking about the black edges on the silhouette but I reviewed the picture and I've reread what you wrote and you did the hard edge/uvsplit thing wrong. You can have any uvsplit without smoothing split. BUT where you have a smoothing split, you need uv split too! And since you probably made smoothing splits at the 90 degrees angles, you need uvsplits there. If you don't want uv splits there (because its harder to texture) you can still add chamfers, so you wouldn't need smoothing splits at every harsh angles.

ChrisCorr

I was getting really frustrated because I thought that's exactly what I was doing. Now I just noticed that because I'm using Cinema 4D, not only does it count the edges I manually harden, but it also has an automatic smoothing based on angle, so those 89º+ angles were getting hard without me noticing.

BARDLER

Read through this thread, and watch the videos posted by EQ: http://www.polycount.com/forum/showthread.php?t=107196.

Quick explanation: On your model you have made hard edges on those harsh angles in your low poly which is a good idea. But your UVs do not match so you get that bad shading in your normal map. Where ever you have a hard edge(smoothing group split for max), you need to have a UV split on those same edges.

ChrisCorr

That's the thing, I didn't set those edges as hard, Cinema4D did that without me realizing, that's why the hard edges don't match the UV splits I made.

I fixed it by disabling Cinema 4D's automatic smoothing.

Thanks!

ng.aniki

I just wanted to precise that in this kind of situation I personally prefer to use a hard edge and split the uvs at those sharp angles.

It is a matter of taste, it has its down side (more chance of having visible discontinuity if you use some other photo texture there).

But the normal map will be a lot cleaner (not huge gradient along the entire surface), and have less chance of having visual artifact due to texture compression (The wider a gradient is, the more chance you will be able to spot the pixellised normal gradient on your model).
And it makes it easier to tweak your normal map texture afterward in photoshop. (If you use photoshop/crazybump/ndo to add details to the normal map)