How to create irrigated terraces with Geomorph

Using the "lift edges" tool and a "water map"

Geomorph 0.40 provides a "lift edges" tool  which allows, when used with the terraces tool , the creation of terraces looking like those irrigated for agriculture.

We use here the technique of the "water map", also featured in the "Eroded terrain with river" and in the "Giant Causeway" examples. Two copies of the same height field are superimposed with Povray, the first one whose edges are raised (the "main terrain") and which has a grass-like texture, the second one (the "water map") with a water-like texture and which was left flat.

A new terraces.pov scene is provided for this purpose. It takes as input the "water field" previously saved as hf_water.png and the height field you are working on, whatever name it has.

The example shown was created in these steps:

Step 1 - Create a standard "Subdivision 2" terrain . The example uses a 512x512 map.

Step 2 - Decrease its contrast by -30 with the "Brightness / contrast" tool . Black areas produce edges looking too high; white areas can produce overflow.

Step 3 - Create the terraces . 6 levels where used in the example, with a smoothing radius of 2 and an artifact removal radius of 12 pixels. "Removing the artifacts" means removing the peaks which appear too narrow, at the higher level.

Step 4 - Clone the terrain using "Copy under a new name" in the menu bar, name the clone hf_water.png.

Step 5 - Crest the water map using the "Crests" tool with the default parameter of 3 steps, so that the water map does not "stick out" under the terraces.

Step 6 - Raise the edges of the terraces with the "Lift edges" tool . Here the default radius of 20 was used, with a level of 15.

Step 7 - You may smooth the terraces with the "Smooth" tool , depending on the look you want. Here a smoothing radius of 4 was used.

Step 8 - Render with terraces.pov.

Like in the 2 other tutorials featuring water maps, the X and Z scales in the terraces.pov scene file can be stretched to improve the result. Here, a scaling factor of 1.7x was used.


Written in January 2007

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