Animated terrain models can also be created. This section shows an example of one type of terrain animation. The short (five frame) animation sequence shows a landscape as the sun moves from a position corresponding to 0900 hours to 1700 hours at a northern latitude of 45 degrees when there are twelve hours between sunrise and sunset. The animation was created in POV-RAY by taking advantage of the automatic slide generation utility within the program. POV-RAY allows variables such as the light source position to change as a function of time. It is necessary to instruct POV-RAY how to move the light source (using Cartesian coordinates) as a function of its internal clock variable in order to produce the desired effect. In this case, it was necessary to convert the time of day, latitude and distance to the "sun" to POV-RAY light source Cartesian coordinates, the origin being at the center of the image. The resulting animation sequence allows the terrain to be studied under lighting conditions corresponding to different times of the day.

Once you have prepared the slides in POV-RAY, you will need some animation software to create the .jpg (animation) file. There is a lot to choose from. A good program for beginners to try out for free is GIF Movie Gear. It is quick and easy to use for simple animations. The result of animating the slides created automatically in POV-RAY is shown at right.

I created a utility to assist in image overlay and animation. Once you have your DEM base file and overlay file (in TGA format) you can use my program DEMDRAPE2 to create a POV-RAY script file (and requisite .INI files) by following the directions on the menu. The script file will allow POV-RAY to render images like those shown in this section and the one preceding by opening the script file and clicking on 'Render/Start Rendering'.

A slight variation on this technique would animate the POV-Ray camera position as a function of time in the same manner as the light source was animated above. This would have the effect of creating a "flyby". Since there are other ways to do this using other applications that are a little easier, this is left as an "exercise for the reader".