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I'd like to bake a normal map for a simple object, but unfortunately, after the bake, the edges of the low poly model are visible on the normal map. The image size is 1024x1024px, if I increase the size it's better, at 4096x4096px it's barely but still visible. Auto Smooth turned off for both objects and set to Smooth Shaded, also there are no sharp edges.

Is this how it should look like or there is something that I didn't take into account?

Images: 1024px normal map, image of the problem.

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  • $\begingroup$ When setting up your bake texture, did you enable 32-bit float (highly recommended)? $\endgroup$
    – Christopher Bennett
    Commented Jan 23, 2022 at 17:39
  • $\begingroup$ I tried with and also without it. The result is the same. $\endgroup$
    – Tsybe
    Commented Jan 23, 2022 at 17:47

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One option here is to add holding loops to the low poly. The triangulation won't matter if we're interpolating between vertex normals that all point in the same direction:

enter image description here

I just selected the top faces and 'i' inset. Now you can see that the artifacts in the low poly's normals disappeared. Note that they didn't go away entirely: they still exist on the edge. We've just confined the artifacts to a small enough portion of the mesh that we'll never ever notice. When we bake, that inset portion will be 100% okay:

enter image description here

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  • $\begingroup$ Thanks for your detailed answer! If I understand correctly, these edge lines on the normal map can't be removed totally, it just can be reduced to a level where it's hard to notice, right? Is it true to any normal map and just I didn't notice it yet or just to flat surfaces like in this case? $\endgroup$
    – Tsybe
    Commented Jan 24, 2022 at 0:50
  • $\begingroup$ I tried your first advice, to reduce the extrusion value. I baked a normal map with the same value you used, but unfortunately, I couldn't see any difference between this one and a map baked with a higher extrusion value. Can it be caused due to some settings? Also thanks for sharing your technique to estimate the extrusion value. The second advice works pretty well, but of course, this requires more vertices, that is in this case wouldn't mean that much, but I'd like to avoid it if it's possible and try to figure out the first option, or maybe some alternative. $\endgroup$
    – Tsybe
    Commented Jan 24, 2022 at 0:51
  • $\begingroup$ Yes, there are basically always going to be some artifacts, and the best you can do is minimize them. You make stuff to the quality you need, not to some unattainable perfect. It may be possible that I'm misunderstanding your problem; I couldn't see the issue in your pics, and focused on the issue that I could see in the file. $\endgroup$
    – Nathan
    Commented Jan 24, 2022 at 1:47
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    $\begingroup$ It might be in my head :) I'm not sure my reasoning holds up. I mean, I believe the altered normals, combined with distance to mesh, is reason for the lines. But now my thinking is that ray extrusion wouldn't do anything to fix it. I may do some more testing and edit the answer. $\endgroup$
    – Nathan
    Commented Jan 24, 2022 at 4:17
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    $\begingroup$ An alternative is an object space normal map, which is baking fine. Unfortunately, again, rebaking that to tangent gets the same issue. $\endgroup$
    – Nathan
    Commented Jan 24, 2022 at 5:35

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