Back faces of model doesn't receive light with normal map

Support Lighting and Rendering
1

Hello, this is my first post here after hours of digging through the internet and not finding any solution for the weird problem i encountered. I’m trying to achieve a painterly effect by following this tutorial: https://youtu.be/s8N00rjil_4?si=v6Shvpf-BNWSStJD .
Basically, the tutorial exports and manually edit the normals for the effect. For the most part, the process turned out fine and i was really happy with the result. That’s until i turned to the back…

dfv
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For some reason the back of the model is hard-blocked with a clear edge, everything is total black. I have a blue back light but the turtle neck doesn’t pick up any light from that source either.
The tutorial said to change the color space to Non-color, but i found that sRGB still works and produce a better look. I tried changing it to Non-color, but the problem persists. I tried color picking from the front to paint over the back on the normal map and the lighting still updates, which means there has to be something wrong with the blue color for some reason.
Does anyone have any clue on why it is the case?

2

Welcome!

The normal map in the screenshot seems to be an “object space normal map”. Did you try to plug it into the material like you would any regular normal map (tangent space)? Because that’s not going to work. You would have to set the normal map node to object space.

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Unfortunately I wasn’t able to include a screenshot of my node setup, but yes, i just plugged the image texture right into the normals of a principled bsdf node. When i put a normal map node between them, the result came out very weird in both object space and tangent space. I don’t know if it’s because my blender is not updated enough (3.6), but either way, thanks for your reply. I kinda just gave up and move on with the rest of the scene since the back won’t be visible anyway.

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