Displacement and other “moving” devices will create artefacts because WM only knows the value of pixels in our extent.
Terrain overhead, a user defined distance of “extra” terrain in all directions, from which the Displacement device or other “moving” devices can get data so that “unnatural” edge handling can be prevented.
The Displacement device is somewhat limiting when creating feature defining distortion, as the terrain near the edges will often have unwanted behaviour, such as weird mirroring. When there is some overhead terrain, the device can, instead of immediately performing some sort of edge handling, creating for a much more natural looking terrain, without strange artefacts.
- Requires more RAM and CPU power, as there will be a significant amount of data stored “outside” of the extent, which needs to be stored and updated as well.
- When placing multiple “moving” devices after each other, you will eventually “run out of” overhead, bringing you back to the problem to begin with.
- Probably confusing for newcomers.
Side-effects (a probably incomplete list)
- Because there is now invisible terrain, you may get results from natural devices that come from features outside of your extent, for example, talus or deposition from a cliff you can’t see.
- The Flow Restructure device now may show some weird behaviour, as it also takes into account terrain you can’t see.
- Blurs and Expanders will have bleed from the overhead terrain.
- When normalising the terrain, your extent may not normalise as expected.
- Masking, though this creates its own artefacts as, for a magical reason, the distortion stops near the edges.
- Exporting at a larger resolution and size than planned, so you can cut away the edges where the artefacts take place.
- Using the built in distortion or Distortion Generator device to distort the terrain generators and let them do the “heavy”, terrain defining distortion and only using the Displacment device for small distoriton, though this only applies to the Displacement device.