Pbr terrain improvement

[BlackYps]

Instead of layering two textures at different scales we now sample at the same scale but with two different rotations. Then we blend between them with a relatively sharp transition to make the visual texture repetition go away.

[Garanas]

There's a tiling / square-like pattern when you're zoomed out:

[BlackYps]

It looks like that is because the textures in the atlas are bleeding into each other. This will be tricky to get rid of

[Garanas]

Ah, I see now

[BlackYps]

We can fix the bleeding once and for all if we have some texture space to spare. If we repeat each texture once, so we have a 2x2 layout of each texture and then only sample the middle, we have enough padding. Of course this doubles the texture size

[BlackYps]

I'll take the atlas bleeding issues to a separate pull request