So I noticed while starting to make a BeamNG map of Death Valley (the real life one), the heightmap abruptly cut off from ~100ish feet to 0 feet elevations, and negative elevations were not even included. So apparently, parts of terrains with negative elevations will be flat.
Ofcourse a heightmap is not capable of negative elevations. Its simply not what its capable of showing. Its only a grayscale with a range from 0 to 1, with 1 being white, 0 being black, and everything in between as the rest of the grayscale. If you want negative elevations, you're going to need to do the heightmap with the lowest point being 0, and align the terrain in game to be at the correct elevation. If that doesn't work then Idk what to tell you. As for your other issue, I can't seem to figure out what you mean by the heightmap cuts off 0-100 foot elevations.
If you have a professional program that's properly configured, your lowest elevation should always be '0' . Doesn't matter what your average or highest/lowest point REALLY is in regards to real terrain on Earth, It needs to be set in the program and the game to start at 0. You can then use an altimeter, and find out how much you need to lower the terrain in the editor after importing to make it work in-game. So basically, if your height of the area is -400m to +460m, you'd work it as if it was 0~860 meters in elevation. Black will always be the lowest portion of the height map and white or light grey will always be the highest portions. Your height map of death valley may need bathymetric data included to go below 0 elevation, otherwise it will just be 'black' and hence flat - even though there's no water there, Sea level is generally considered elevation of 0. Bathymetric data is generally given to map out the bottom of bodies of water, otherwise height-maps are made and the surface is 'flat' where the water surface usually is. Then with that data 0 would still be the lowest point in-game in the height-map even though that may correspond to say -250m or whatever the floor of Death Valley is. The data from 0~100ft elevation (36 meters, IIRC), would get cut-off if the instrument used to record the data wasn't that good.
