Recommendations for References

If you do not plan to use Mutators and plan to use materials of the reference (i.e. ApplyMaterials is True in Reference Properties), then the base layer of the PBR materials of the reference and the map should be the same.

Generally, there are two types of references:

Type 1 – "natural" references, where there is no water or objects.
Type 2 – references that contain water or objects.

There are two sets of typical values of reference properties for these types.

For Type 1, you can use the ability to completely adjust the reference to the map. I.e., you can set up the reference so that it modifies the level for itself only slightly. In this case, typical settings of the reference are the following:

Flatten = False
ApplyMaterials = False (True is also possible)
ApplyMergeMap = True (so, typically you need to specify the RefMergeMask, see RefMergeMask brush).
MergeMaterialMasks = True
ApplyDistributionMergeMap = True
WetnessBlendMode = Add (Replace is also possible)
Snow = Replace

Type #2 is the most common and universal. We recommend you to make the terrain below it rather flat to avoid sharp differences in height at the reference border. For this type, the typical settings of the reference are the following:

Flatten = True
ApplyMaterials = True
ApplyMergeMap= True (so, typically you need to specify the RefMergeMask, see RefMergeMask brush).
MergeMaterialMasks = True
ApplyDistributionMergeMap = True
WetnessBlendMode = Replace
Snow = Replace

On the map, at the location of the reference, we recommend you to remove all plants. However, if necessary, you can leave some plants on the map at the edges of the reference area.

If your reference contains a river, the river colors from the reference may override the river colors of another river on the map near it. The usage of river colors from the reference is the default behavior in this case. However, if you set the AboveReferences field of your river on the map to True, you will protect its river colors from overriding.