Help! Green Normal Map Part is Shading Black!

VanessaCeline

So, I have been trying to go around and understand normal maps recently. This is what I understood: 

• Every sharp beveled edge or edges with a 90 degree angle need to have a split edge in the uv map. 
• The edges mentioned above should also have hard smoothing.
• Every UV Island needs to preferably have it s own smoothing group.

The mesh I have, low poly, as well as the high poly I used for baking, are from ZBrush. I first got them into 3Ds Max to scale them properly. They are scaled at the same time so they should fit pretty well with each other. But what I am actually wondering about, because the mesh looks fine without a material in most places (2-3 small exceptions), but with a material applied, the shading starts being weird in the green parts:

• Why does the green part show up black in the shading of the material?
• What did I do wrong and how can I get the edges beveled nicely in the normal map? I was thinking of doing that in photoshop but I can't really go ahead and do it with the clone stamp tool since it needs to be a straight line...

Mink

"Why does the green part show up black in the shading of the material?"

A normal map perturbs the "normal" direction of a pixel. In substance painter, the shading of a pixel in its realtime rendered view is determined by a lot of factors. Basecolor, roughness, and Metalness. And the panoramic image that makes up the lighting. With metallic materials, light doesn't spread, and a non rough metallic surface will only show color when the light reflected into it also has that color light. 


The green normal map means that those pixels are perturbed to be facing downwards, despite the faces not being downward facing, that's now normal maps work. This is your bevel. Those green pixela are facing straight down. The bottom of youe HDRI sphere is black. There's nothing wrong.

rollin

Can you post a pic of the high and low poly model beside and superimposed?
I guess they don't match close enough and that's why the normal-delta becomes too big which looks "strange" 

VanessaCeline

@Mink well... the model is kind of upside down in substance painter, i thought it might be because of the light, but this problem also shows up in unity. I checked on a metal material i have at home, and you are right, but at the same time i feel like the effect is perhaps a bit to intense and spread on my bake.

VanessaCeline

@rollin here's the screenshot. I know that for some reason it does not align perfectly (it was a zbrush export from subdivisions, they should both have the same pivot i believe), but, the problem with the green lines / black shading occurs on almost all sides with beveled edges, even if the model is slightly inwards, or slightly outwards, also if i change the settings for the bage in substance painter it is the same, no matter what settings i choose. Shouldn't it at least change some of that effect if i change the settings? It only goes away if i set the values to 0.001 but then nothing bakes basically.. 

rollin

Is 'green' always shading black? even if you look at the spot from very shallow or steep angles? If you look from below up, is it really still shading black?

Anyway. My advise is to:
- fist make one UV-shell, one smoothing group of the objects shown.
- Straighten the uv shell.
- Then make sure the high and low are _really_ lining up when being baked.
- Bake in another app for comparison

VanessaCeline

@rollin What app would you suggest for that? I wanted to try marmoset but my high poly makes in crash, since it's too high poly probably I have subdivision levels so i could get it down more. 

rollin

I don't know what software you have at hand but e.g. xnormal can bake very large meshes if your hardware is powerful enough.