Black lines on simple plane mesh

As you see on this model, which is three planes joined together, there are some faint black lines going through through the middle of all three planes.

However, I made two UV maps in blender which both look like this:

Given that I’m using a material that’s nothing but a white basecolor with white emission, I don’t understand what it is that could be making these weird lighting effects. All my other meshes render just fine with those sorts of UV maps, so I’m unsure what’s happened to this one…

Hi!

Can I ask what is the size of your lightmap?
Also… because its one continuos plane I would have my lightmap one (!!) island as the shape of the plane!! Like a top flat map!

Good luck! :slight_smile:

The lightmap resolution is currently 4, but I’ve tried many others and the result is the same.
What does it mean to have the lightmap as one island? I’m not very familiar with UV mapping, so I don’t understand what that means.

Hi!

I think 4 is way too low!! …but if you say you still get the same at 128… :S
Lightmap uvs (2nd uv channel): have the same shape as the mesh in 1 piece…

If you set the material to 2 sided?

It appears you’re right! I tried changing the angle of the lighting, and that changes the position and amount of stripes. Some angles have none of them. Turning off dynamic shadows also removes the stripes, so I don’t think there’s any doubt. If you post this as an answer, I can mark this as resolved.

I would bet that stripes, as displayed on the screenshot at least, are result of dynamic shadow filtering with a light shining at glancing angles on the surface.

These artifacts are commonly known as shadow acne. You can slightly reduce it by increasing shadow bias setting on your directional light. More in depth info about the cause of these and ways to deal with it can be found in this forum thread and in this article.