Digital Elevation Model (DEM) Terrain Displacement

You will notice that we scaled the flat NURBS plane in all 3 axis. (X, Y, and Z) The reason for this is because Maya calculates displacement as if it were a volume. If you have a flat plane and you leave it's scaleY value at 1, it will not displace properly because it only has 1 unit of volume to work with. You need to scale your plane in Y to a value at least that of your target displacement. Since we do not know that number yet, I just scale all 3 values the same amount. The reason for 614.4 is because I prefer to work in 1/10th scale. This eliminates all the potential problems Maya has when dealing with larger scaled scenes. So, since our TIFF image is 6k (6144 x 6144) it's a straight conversion to 614.4 x 614.4. The patches 25 and cubic are going to come into play when we convert the displacement to polygons later.

With your plane selected use the pull down: "Window > Rendering Editors > mental ray > Approximation Editor..." In the Approximation Editor you want to click the [Create] button next to "Displace Approx." Next click the [Edit] button and change the Presets to Fine View High Quality. This is just a default preset for the Displacement Approximation and works well for our purposes.

Create a new Lambert shader and click the "Output Connection" button located at the top of the Attribute Editor.
Then click the map button next to "Displacement Mat."
Then click the "File" button in the Create Render Node window.
Click the file tab and then map our TIFF image to the "Image Name" field.

Now you can render your image to see how things look. You will see a small amount of displacement in the image, but not quite what we are going for. Open the Attribute Editor for our file node and expand the Color Balance folder. This is where you dial-in your displacement height. Enter a value of 10 for "Alpha Gain" and then select your NURBS plane. In the Attribute Editor for your plane, expand the Tessellation folder and check the box for "Display Render Tessellation". Check the box for "Enable Advanced Tessellation" and change the Number U and V to a value of 5. What this will do is increase the number of faces your NURBS plane has based on its spanU and spanV values that we earlier set to 25. The Attribute Editor says that the "Triangle Count" will be 31250 for our plane, but that is WAY off. With your NURBS plane selected use the pull down "Modify > Convert > Displacement to Polygons". This could take a very long time depending on your machine. If your machine crashes, change the Number U and V to a lower value in the "Advanced Tessellation" section we set to 5 earlier. These numbers control how many polys Maya generates when converting the displacement to polys. Lower numbers = less polygons = less memory intensive on your machine.

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