Why Does My Surface Appear Half Dark After Applying It to the Model?

[mrsneuna]

I created a custom surface and applied it to my model, but part of the surface appears darker than the other side. As you can see in the image, the same material looks half dark and half normal. Why is this happening, and how can I fix it

Operating system used: Windows 11

[Laszlo Nagy]

Does it change if you move the Sun around? I would try to change the Sun Azimuth by 90 degree increments in the 3D Projection Settings Dialog, and see if that has any effect on this.

[mrsneuna]

I already tried changing the sun azimuth and adjusting the sun position, but the dark area on the surface remains the same. It seems like the shading stays in the same place regardless of the sun direction.

[Barry Kelly]

It looks to be just that one column that is affected?

If so, what happens if you change the material.

Is the new material affected in the same way?

Or if you move that column, does it still remain half dark?

Barry.

[Gunnar]

Have you tried turning off Sun Shadows?