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Terrain surfaces - a users guide:

In this tutorial we're going to look at controlling how GenesisIV renders terrain surfaces. GenesisIV offers considerable control of surface rendering, which is useful when attempting to replicate real-world landscapes.


We'll use a model of Australia's Uluru (or Ayres Rock) for this demonstration. Note that most of these images are not intended to be particularly photorealistic, rather they illustrate effects of changing parameters.


  

The first image shows the model set up with fairly simple settings, as illustrated by the Terrain Fractalization Editor. We'll use a fractalization level of 2 throughout, with the Tree Line position set at the base of the rock, hence the lower terrain type - Valley - which appears below the tree line can be set as a mixture of green and brown colours. The roughness setting adds large scale distortion to the surface and is useful here to give an impression of a rough scrub.

The edge fuzzyness setting controls how much the three basic terrains mix together (here valley, middle and hilltop corresponding to below treeline, treeline to snowline, and above snowline), and will be left unaltered, as will the bias setting which mixes the two colours - you may wish to experiment.

All the distribution parameters except coverage are unused for the basic terrains, and coverage is only used if a child surface is present (see below).

 
The middle terrain type is set to mix orange/pink colours corresponding to Uluru's sandstones. We've made this slightly smoother - by lowering the roughness - than the scrubland around the rock.  
The hilltop terrain is similar to the middle terrain. Although this terrain type occurs above our 'snow level' setting this is just a useful way of dividing the landscape into three and doesn't have to be an actual snowline.  
 
Our next step is to roughen up the middle surface slightly. Here we've increased the Roughness setting for the middle terrain from 3.0 to 20.0. This adds some additional texture to the surface by distorting the terrain grid.

Because of the edge fuzzyness apart from an increase in roughness around the cliffs, the ground scrub texture also shows a few more orange bumps.		  
In addition to distorting the surface, we can also use the bumpiness, shininess and specularity parameters to change the surface texture. Here we're increased bumpiness for the middle terrain from 0.0 to 0.6, which adds detailed shading to the rocks. Shininess and specularity in this image are both set to 0.0.  
The shininess and specularity settings lighten the surface by adding highlights. In this image bumpiness has been left at 0.6, shininess set to 0.6 and specularity set to 0.3.  
 

Colors and texture information may also be applied to terrain areas. If you're unfamiliar with terrain areas you may like to check out this tutorial which discusses them in the context of adding vegetation.

This image shows a simple polygon terrain area added to the scrubland in front of Uluru. It's been rendered using a garish orange/brown combination to highlight it's position.

  
Surface 1 - the surface used for the polygon, is here shown in the Terrain Layer Editor. Note that as well as overriding colors we can choose to override surface properties, either in combination with colours or as an alternative.  
Here the default colors are used, but the surface bumpiness, specularity and shininess increased significantly, hence giving a much more heavily textured area. Note that in this case the roughness has been set to the same value as the valley terrain, and hence there is no difference in gross surface shape.  
 

Child Surfaces can be added to the standard three terrains. In this example we've added a bright orange child surface to the middle terrain (named band) and set it to appear for slopes between 30 and 60 degrees.

For contrast we've also increased the amount of green slighly on the scrubland in this image.

  
The relevent area of the terrain area is shown here. Note that because the coverage rating is set to 0.35, and the coverage weighting for the middle terrain was 0.1, the Band terrain is mixed in with the middle terrain at a ratio of ~3.5:1 where coverage meets the slope criteria.  
Child surfaces may also be limited by altitude. In this example the min and max altitude settings have been enable, with the result that the orange terrain is confined to a much smaller area than before,  
Altitude settings for this image.  

Generally we wouldn't want such obvious effects as show in the last two landscapes, so here we've reduced the coverage weighting to 0.15, increased the edge fuzzyness to 0.3 and the slope fuzzyness to 0.4. All other settings are as before.

The result is that the band is less pronounced, and spread more widely across the rock.

  
 
Finally, we've shown the image with the sun at a lower angle.