This is a very old thread but there don’t seem to be any others, so going to necromance here for the benefit of others searching.
I didn’t see any UV artifacts, but also had a small landscape (so UV precision is less of an issue) - and didn’t test on a wide variety of devices.
Performance is another issue - Landscape performance on ‘previous gen’ mobile is not good (to be expected, really).
Nexus 7 (2013) - Adreno 320.
UE4 4.9 LDR mobile mode.
Very small landscape - 187x187 verts (31x31 quads, 3x3 components). Collisions disabled. Stretched over a relatively large area (90000x90000 unreal units).
Unlit opaque material (LDR), 3 samplers (base texture, detail textures in RGB channels, lerped by static colors in each landscape layer, combined for final result).
Using landscape layer nodes in a material (vert colors internally?) even on an unlit material can easily double the time spent in the render thread.
Suspect this relates to the tile based rendering of mobile hardware (one extra pass per landscape layer?).
Using an ‘standard’ unlit material with no landscape material nodes works best.
Use customised UV’s in the second (index1) and third slot (index 2) to tile textures - using UV slot 0 as a customised UV does not work on device (bound to landscape chunk UV’s internally?).
Multiplying UV’s of an existing custom UV per pixel for additional detail textures seems to perform OK.
Divide your UV coordinate by the number of vertices in the height map to get a 1:1 mapping (ie. UV divide 187 in above scenerio covers entire landscape once with no repetition).
Getting landscape materials to look good with these limitations is “rather challenging”.
As I had a small landscape area, I was forcing LODing to occur by increasing ‘Landscape -> LOD -> LOD Distance Factor’ from 1.0 to 3.0.
Don’t do this. While it reduces the number of triangles in a scene, it has a large performance hit - it can actually be quicker just to render the triangles than to recompute LOD’s each frame.
I had a 33ms max per frame target (30fps).
In the above scenerio, this landscape LODing was costing up to 18ms a frame depending on the view (more than the rest of the game thread including running as a server).
Hope this helps someone else out there save time…