An Example of DEM Import and Procedural Enhancement

Most files in DEM format are taken from contour maps. This means that these DEMS result in a step-like terrain when imported into MojoWorld, but we can hide and enhance that with procedural data. This example imports a DEM into a plain MojoWorld and uses a single procedural texture leaf to reduce the step-like effects of DEM data.

A note on formats and vertical scaling

The automatic vertical scaling on imports of terrain data takes into account the area of the Parameter Bomb into which the terrain data is imported. The import process finds the highest and lowest point of the terrain being imported and then scales that to be equal to half the width of the Parameter Bomb object. That may or may not be close to accurate, so the 'Height Scale' parameter will probably need to be interactively tweaked to get the desired results. One instance where the vertical scaling seems to get things quite wrong is with some SDTS DEMs. For example, this quick render shows two terrain imports that are each 10 Km square. The terrain on the left is a DEM, the terrain on the right is an SDTS DEM:

This next image is after the Height Scale and Height Offset on both have been extensively tweaked. Now they both look much more like terrains. For the plain DEM, the Height Scale was reduced. For the SDTS DEM, the Height Scale was significantly increased and the Height Offset was set to a very large negative number:

There doesn't appear to be a lot of vertical exaggeration in this render, but this is from an altitude of 10 Km. These next two shots show the two terrains from an altitude of about 20 meters:

Those are both without any extra procedural data added in.

A Specific Example

This first render is a plain planet with a Parameter Bomb that has an X Size of 9000 meters and a Y Size of 12000 meters (approximating the area covered by a single 7.5 minute DEM, though actual exact sizes will vary across all DEMs depending on the latitude range they cover). The DEM has been imported and no other parameters changed. Note the step-like terrain:

In the terrain texture created by the import process, create a second texture leaf by clicking on the ghosted circle-T. Click the circle-T again to open the texture leaf's kickstand. Name it something like 'procedural detail'.

 

The scaling of the added detail will depend on how large the Parameter Bomb is. A general rule is that the procedural detail should have a Largest Feature Size no more than a few percent of the size of the shortest dimension of the Parameter Bomb.

There are two different approaches to the output and blending of the procedural data. One is the Add method, where the procedural data leaf is added to the bitmap leaf. In this case, the procedural data should output values that range between plus and minus about half the height of the step features in the bitmap that are to be masked by the procedural data. The second is the Multiply method, where the procedural data leaf is a multiplier of the bitmap leaf. In this case, the Input Curve in the Output Control should be set up to keep values between 0.8 and 1.2. This following example:

was created from the first example using the Multiply method. The Input Curve on the procedural data leaf looks like this:

 

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