Here is a short account on how I managed to use available topographic data to generate realisitic terrain in 3DSMax. I’m sure there are other ways to do it, maybe better, but this is just intended to save time to some who try to do the same stuffs.
USA National Elevation Datasets
Use the download by bounding box option and then select what you want to download, in this case most likely ‘land cover’, ‘elevation’ and ‘orthoimagery’.
When asked about data types, Elevation should be asked as ‘GridFloat’, with 1/3 arc second if available.
Get the links by email and download all that.
To process these data, specially elevation, you will need a free software called MicroDEM. This tool will translate the ‘raw’ data into usable greyscale images.
After unzipping all you downloaded, open the .FLT files one at a time inside MicroDEM. If asked to ‘Open as 16bit integers’, click ‘NO’, because we want to have the floating point data. Before you convert anything, you will need to go into Options>Import/Export, and change the GeoTiff grid save option to 4 byte real, in order to have a floating point format being opened and saved, that will later become an .EXR file.
Go to Overlay>Manage Overlays options and deactivate ‘grids’.
Go to Modify>Elevation and ask for ‘Gray scale’.
You can then File>Save DEM>GeoTIFF to output the conversion.
Don’t use the ‘Save image’ or ‘Save map as image’ options, they will destroy the floating point info.
Repeat if you have more than one DEM file to process.
Open the .TIF files in Photoshop. If all went well you should have a fully white picture, and it should says Gray/32 in the title bar, which means we are in floating point mode.
Go to Image>Mode>RGB Color to activate RGB, it is useless, but PhotoShopwill not let you save as .EXR otherwise.
Above your white layer, create an ‘Exposure’ adjustment layer, and tweaks its exposure settings until you get the elevation informations back in the visible range of colors. For me it is around -12. Do not change Offset or Gamma.
If you have multiple .TIF files, use the same setting for each.
Then save each image as .EXR
You can now load these .EXR files directly as displacement map inside your favorite 3D package.
Here you can see the result with the Grand Canyon.