Mirror normal map problem

Fomori

Hi all. This is my second attempt at a model using the high poly > low poly > normal map workflow (so go easy on me) and I really wanted to optimize the texture space on this axe model.

I've been reading up on mirroring the normal maps and seen this problem around. The solution I found is here:

http://www.polycount.com/forum/showthread.php?t=51088

But that doesn't work for me (see my images below). I'm pretty sure I've followed it closely and I even tried the green channel after the red. I've also moved the mirrored UVs one unit across which I've read you are supposed to do before baking. As you can see from my maps I'm trying to mirror along the x axis as well as the y to save as much UV space as possible.

Clearly it looks like parts of the normal map are inverted, look at the eyes, wings and the big dark patch. Some parts look ok though. Any help sorting out the problem areas I've pointed to would be a great help. Thanks.

Fomori

Ok, the darkness at the edges of the blade seems to be a smoothing group issue. Everything was one smoothing group but I changed the edges to have their own. But still have the problem with the normal map mirror......

Ben Apuna

Did you rebake after fixing the smoothing groups?

Did you use a mirror modifier to mirror the geometry? I've heard that those can invert the face normals (or something like that), and that a symmetry modifier is better for mirroring.

For mirroring normal maps all you need to do is move the mirrored UVs one unit over then bake. Do not delete half of your mesh before baking. One other thing, make sure that the mesh triangulation is mirrored as well.

Fomori

Ben Apuna wrote: »

Did you use a mirror modifier to mirror the geometry? I've heard that those can invert the face normals (or something like that), and that a symmetry modifier is better for mirroring.

One other thing, make sure that the mesh triangulation is mirrored as well.

Ah, I didn't use the symmetry modifier. I cloned the polys I wanted to mirror, mirrored them and welded them back onto the model. Will try the symmetry modifier now and report back.

By the mesh "triangulation" you mean the hidden edges on 4 sided polys yes? So when you go to edge mode and hit "turn" you can see the triangulation?

Ben Apuna

Yeah the hidden edges. Max is so awesome with that turn thing, I wish other apps had that ability.

Fomori

Well, bit of a strange one. I've tried it with the symmetry modifier and I still have the same problem. But I decided to throw it into Marmoset and the mirror seems to be functioning fine. A bit perplexed now.....

eld

Split both halves into their own smoothinggroups, so that you'll get a hard edge where the mirror-seam goes, bake it like that aswell, that should remove any mirroring artifacts.

Fomori

That did seem to help the look on the actual model eld. Thanks.

Still can't get it looking right in Max though, maybe I just haven't set the viewport shader up properly. But looks fine in Marmoset which I want to render in anyway, so will go with that.

Don't know why, or if others do this, but I noticed that the normal map baked with the whole model as one smoothing group looked better than the normal baked with certain smoothing groups separated (put onto a model with separate smoothing groups). The normal map with separate smoothing groups had black outlines in Marmoset (this wasn't pixel bleeding or whatever as the map had the blue fill).

EarthQuake

You need to have UV seams where your hard edges(smoothing groups) are, or else you will get "seam" type artifacts.

Scruples

Try the 3 point shader for max, http://www.polycount.com/forum/showthread.php?t=72861 .