When you select "paint ground" in the editor you can not then select "paint ground + shift" to remove the painted ground image. This procedure produces a ghost image. See attachments
The only sequence I can find around this problem is to place mud or sediment over the ghost image then use the "paint ground + shift" and paint over the mud or sediment image. The puts the terrain area back to the original.
Windows pro 8.1 with 8.1 update,64 bit|AMD FX-6200 Six-core-3.80 Ghz |CPU PASSMARK 6,142 |Memory 10GB |NVIDIA GEFORCE GTX 660 SC |GPU PASSMARK 4,114
