I recently received an email recommending the scene rendering application called Terragen. This program is absolutely the best application for displaying terrain models as stunning photorealistic images.

Terragen requires its elevation data in .ter format. This format is similar but not the same as the TGA format that POV-Ray accepts. Its elevation values are represented as a series of two byte integers rather than the three byte format the POV-Ray uses. Also, it is not possible to view a .ter file using Paintshop Pro or other graphics program.

In order to provide data for Terragen, I modified SDTS2POV so that it output .ter files instead of TGA files. I named this program SDTSTER4. It accepts USGS 7.5' DEM files and outputs a .ter file that can be used as input to Terragen. I provided a prompt that allows the user to input an elevation scale factor. Try 30 to start and adjust from there.

When you convert and open the file you should see a familiar-looking grayscale image in the Landscape and Image windows. Hit the "render preview" button and the grayscale will be converted to a 3D elevation model. There are several very nice features of Terragen. The first thing that you will notice is the presence of a sky. Terragen has the ability to easily add a realistic sky sphere section to the image. The second thing you will notice is the interesting surfacing algorithm. A very realistic looking surface is rendered such that it does not look faceted no matter how close the viewpoint gets to the surface. The surface texture is very realistic as well. Terragen allows placement of a visible "sun" that casts shadows both from the terrain and from the clouds.

I added some color to the image by applying one of the supplied surface maps. I chose the grass and snow surface and modified the snow in order to create a more or less distinct snow line on the mountains. I could have done better by constructing a tree line as well, but I have not figured out how to do this yet. Regardless, the results are pretty good considering my lack of experience with the program.

My test image is shown at the upper right. The grayscale image from which it was generated appears below. The scribes on the grayscale image depicts the camera location and field of view.