L3DT Users' Community

Most DEM's available only cover the above water elevations.

How can we use L3DT to produce some elevation data for the underwater parts of these elevation maps/heightfields without affecting the above water parts we are happy with??

In theory it must be possible with lots of work, but can L3DT do this easier ?

Any thoughts ?

You would need some basic DEM reference that had the ocean data included (or sculpt some rough ocean basins into the data you have).

I would save a copy of the DEM w/ocean-data in a L3DT project, and erode with the usual Import as Design Map workflow to generate detail at the desired horizontal resolution.

Then, use the new "Merge Heightmaps" features (see that thread) and a suitable mask to blend that into your original data (everything above 0m would be black, and the edge into the negative altitudes would fade through a gradient, depending on how you want to blend the shorelines). You would want to play with blending modes and mask gradients to see what would look alright.

The locatation in question is rather remote and and it was hard enough getting a standard dem with above water features, below water I have found is near impossible.

Creating my own is a possibility but would take quite some time due to the nature of the coastline.

For those wondering, its South Georgia, South Atlantic ! (Not USA)

I don't want to insult your intelligence, but what you are looking for is bathymetry (wikipedia link here). If you do a search for that term in your area of interest, you may get lucky....

I agree with what Telarus suggests to create your own bathymetry, though. Work from what you have, create erosion for the underwater areas, create a mask (to protect the land areas) and then combine the two heightfield maps.

One thing I wish was possible was to create a mask and then run the erosion effects. This would be great for many applications, not just the example here. Hopefully it's in Aaron's "To Do" list for vers 3.0.

Allan