How do I fix this very rough sort of lighting in Eevee?

Question

I am making a simple render consisting of cubes and the lighting looks like this and forms weird edges and triangles on the faces, and it looks horrible on renders. I don't know how to fix this nor do I know what I did to undo it

Answer 1

In Eevee, this could be either having too few render samples, or messed up Shadow settings.

Render samples

The default 16 samples should be enough already, make sure you have at least that.

Shadow Settings

The two main things here that you should check are Soft Shadows and Cube Size.

Shadows are basically a calculated and stored in a picture file in Eevee. Soft Shadows will "smoothen the pixels":

Cube Size is the size in pixel of the captured shadows. Bigger is better, but heavier.

If you use the default parameter, most scenes should be fine, but you can go higher on more complex scenes.