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Digital Elevation Model (DEM) Terrain Displacement
Digital Elevation Model (DEM) Terrain Displacement
DezFX, updated 2006-02-25 10:23:33 UTC 146,012 views  Rating:
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In this tutorial you will learn how to create the image seen below using displacement in Mental Ray for Maya.

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Mt. Rainier

To follow along with this tutorial you will need the following software installed on your machine:

* Note: You can use an older version of Photoshop, but you will be limited to 8-bit TIFF file output. With Photoshop CS you can export 16-bit TIFF files for finer displacement.

We are going to be building a digital version of Mount Rainier using satellite digital elevation maps (DEM) and displacement inside of Maya with the Mental Ray plug-in. One key factor to remember while following this tutorial is ORGANIZATION! There will be a LOT of information covered here and you can get lost really quickly. Keeping things like file names and subfolders organized will help you keep things manageable along the way.

DEMs are greyscale photographs taken by satellites in orbit of the Earth capturing terrain elevation values. These DEMs are broken down into approximately 6.5 mile by 7.5 mile sections called quads.

Before we get started you will need to create two (free) accounts to gather the images needed for this project. One account will be at the USGS Quads site which will be used to determine what quads make up the area we will be building. The other account will be at the Geocomm website which is where we will be downloading the quads from. You have the option of setting up a pay account at Geocomm. When you pay for a premium account you get a faster connection speed for downloading. Or you can just use a free account and the downloads will take longer. The typical connection speed is limited to 3-5 KB/sec for the free account. I am not 100% sure if the download speed is based on IP address or your log on account. When I download with several machines, that are behind a single IP address router, the total speed is spread over each download and you can achieve blazing speeds of 0.2 KB/sec. So, I just find it better to let one download have all the bandwidth and find something else to do while you are downloading. The average file size is 2-4 MB usually resulting in around 10 min to download each quad. The other option would be to have Geocomm burn the DEM data to a CD and mail it to you for a fee.

The quads are sorted by county on the Geocomm site so you will also need to locate the county names for your target location. I usually do a search on Google for " county map" and within the first few hits I can find a good image to go with. This is the county map image I found for Washington State.

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Sometimes, as with this project, your quads may span two or more counties depending on their location. This is where it's helpful to have a map of what counties butt up next to each other.

After you have your counties image, go to the USGS Quad finder site and under the "1:24k Search" navigate down to Washington in the list and click it.

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This is where you will need to have an account created. When you locate the section of quads we will be needing you will find that some of our quads are located in Pierce County and some are in Lewis County.

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I've added the red line and county names to our map for illustration. This is where your research skills come into play in determining county lines.