Mesh Distance Field Artifacts on Older GPUs

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.

1. Open Kite Demo on UE 4.18.3
2. Open level Forest_and_Lake
3. Create material consisting of "Distance Field Gradient" normalized and plugged into the Emissive output
4. Apply material to SM_WaterPlain
5. Move camera around lake

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.