However, every time I add a surface, the lines pop up on the previous surface, sort of like a see-through, in spite of all kinds of opacity is turned all the way up. Furthermore, it only does it from certain angles. The tutorial doesn’t say anything about this problem, and I have no idea how to fix it, it’s driving me nuts.
Indeed, in tutorial, he is using 2D layers as Stroke Depth Order.
Camera movement is not a 360 degrees rotation.
He is just fixing order of strokes by using Stroke > Arrange menu for main viewpoint.
Or he is using mask.
If you want an occlusion of strokes related to their position in 3D space, you have to change Stroke Depth Order to 3D Location, in Strokes panel of Grease Pencil properties tab.
But as consequences, order of Layers will stop to have an importance and Fills overlapping, at same plane in space, may look bad.
That can be fixed easily by maintaining a slight offset between drawn planar surfaces.
