your panoramic views, as the rendering in this colorless world
is quite fast.
Whether working with the fractal-based terrain or USGS DEM
data, we can improve on the terrain data with enhancements
that include creation of striations for sedimentary rock or
adding boulders or extreme rock outcroppings. Displacement
is the terrain simulator’s term for creating variances in the
terrain. In my scene of Virgelle Montana, the DEM data did
not have sufficient resolution to show the sedimentary stria-
tions on the sheer cliffs along the Missouri river. I was able to
add these features with the Terragen using a strata and out-
crops shader. [8]
As inspiring as even just the grayscale terrain images can be,
the real fun starts when shading is added to the scene. Shading
is the term for applying multiple layers of color to the terrain
to simulate vegetation and soils. Again Terragen employs frac-
tals to generate areas where color is placed, the color itself,
and the addition of displacements to provide a 3D simulation
of vegetation. The shading process is accomplished by layering.
Just like the real thing, we layer-in dirt and then layers of vari-
ant vegetation, depending upon the scene.
Shaders have a number of controls for how shading is applied
to your terrain surface. Slope and elevation provide key con-
trols that affect where the shading layer appears. For example,
you can filter a shader so a steep slope will not have grass and
the underlying rock color will show through.
A painted shader node provides ultimate control by allowing
you to literally draw areas on the terrain where shader lay-
ers should be applied. Control here is rather crude, but I used
Computer-generated backdrops - 7
8. The top photo shows a rendering of the raw DEM
file. The second image includes addition of fractal
displacements to fill in the surface with more realistic
texture. Finally sedimentary striations are simulated with
special fractal layers, creating additional details.
8
MRH-Jul 2014
