Mesh Distance Field quality varies greatly depending on GPU.
Per UDN Licensee:
On the GTX 670 machines we can see a very blocky, low-res result that behaves in weird ways when moving around the level in-editor. This doesn't happen on the GTX 1080 workstations.
Result: GTX 670 produces very blocky, striped artifacts on the SM_WaterPlain mesh. On GTX 970, the artifacts are present but much smoother. See attached screenshots.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-56152 in the post.