Digital Elevation Model (DEM) Terrain Displacement
Now you want to open all of the *.raw files you created with PullSDTS. When you select a *.raw file to open you are greeted with an options box. For the "Dimensions" you need to enter the Width and Height values from the quad names we saved while exporting from PullSDTS. (...971x1401...) Then you want to set:
  • Depth = 16 Bits
  • Byte Order = IBM PC

Repeat this process opening all 15 *.raw files into Photoshop. Next you need to drag the "Background" layers for each of these files into our 8100 x 8100 image we created earlier. Lay the images out so that they match the quad layout from our USGS Quad diagram. As you are dragging them over you may want to name each new layer apropriatly. I also drag them in order from the top left quad across to the bottom right quad. This way it keeps the layers neatly in order inside the new image. You will need to set the "blending mode" to Lighten for each layer. This is so that when you start butting the images the black border will disappear leaving you with only the greyscale image. This is also why we set the background color of the new image to Black.

Now you will need to zoom into the streets between your quads and move them all together. When you get in closer you will note the edges of each quad have a stair step pattern to them. These "steps" mate together and form a seamless image. After you have butted your quads together, you want to merge all of your layers into one for our final output. You will also note that we are now using less than our image size of 8100 x 8100. You always want to keep your image square and a power of 2x. So, you can crop the image size down to 6k (6144 x 6144). I find it easier to start large and then crop it down later. Save the image as a TIFF file format. The output file will be fairly large. This one should be about 215 MB which is average for a 6k, RGB16-bit TIFF file.

OK, you are finally at the point where you are ready to launch Maya and start displacing. Open Maya and create a NURBS plane with these settings:

  • scaleX = 614.4
  • scaleY = 614.4
  • scaleZ = 614.4
  • patchesU = 25
  • patchesV = 25
  • degree = Cubic

This is why we need to make sure the Photoshop image we are using for displacement remains square.
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