I am creating a landscape scene, and to get clouds I scaled a cube by a lot in x/y directions and set its material as follows:
A quick render resulted in the following pattern:
It is possible to see transparent horizontal lines in the clouds. Above image was rendered with 16 samples. Higher sample counts (like 4096 or more) resulted in smoother, but still visible lines. What could be causing this? Note: a workaround by translating the vector or changing the scale (even slightly) is possible, but I'd like to know the underlaying cause.