Draping an Image over Terrain

You can drape an image over terrain using POV-Ray, a free raytracing application.

Step 1) In MacDEM use the "Export Elevation Data to POV TARGA..." menu option to create a TARGA elevation file and a POV-Ray scene file.

Step 2) Using Display Settings, turn off Lighting. All shadows should disappear. Select the desired palette. In this example, the "Atlas" palette was used.

Step 3) Use the "Export Image to TARGA..." menu option to create an image of the DEM without shadows. (The shadows will be created later when POV-Ray renders the scene.) In this example the file "kokohead_elev.tga" was created. This is the image that will be draped over the terrain.

Step 4) You can edit the image created in step 3 to draw in roads or other features. Or you can use it as a guide for scaling, aligning, and cropping another image. Make sure you don't change the size of the image. And make sure you don't edit the TARGA file created in step 1. The image below shows the kokohead_elev.tga file after drawing an arbitrary red line on it in Photoshop.

Step 5) In the POV scene file created in step 1 you will find this code:

//UNCOMMENT the next 4 lines and set the file name to drape an image
//pigment {
//   image_map { tga "YOUR_FILE_NAME_HERE.tga" once interpolate 2 }
//   rotate <90,0,0>
//}

Uncomment the four lines of the pigment directive, and put the name of the file (created in step 3) where indicated. In this example the result was:

//UNCOMMENT the next 4 lines and set the file name to drape an image
pigment {
   image_map { tga "kokohead_elev.tga" once interpolate 2 }
   rotate <90,0,0>
}

Step 6) Render the scene in POV-Ray. Below is the result of this example. Note that the gray edges could be eliminated by converting the voids to zero prior to saving the draped image in step 3. However, this probably would create a blue strip in the mountains along the left edge. A better solution would be to crop the DEM to eliminate the void data prior to step 1.