Fluids: Liquids and Gases - Computer Animation: Algorithms and Techniques - page 266

A GUI used to control cloud formation B Example clouds

FIGURE 8.13
(A) An example of cloud dynamics GUI and (B) example images created in Maya TM .( 1999 Rchi Gartha.)

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heart of Ebert's volumetric approach are implicitly defined density functions that provide high-level
organization of the cloud, combined with turbulence functions that provide the fine detail.
The implicit function used here is really a sum of individual spherical implicit functions. Each of
these spherical functions maps a point in space to a density based on the point's distance from the
sphere's center and a density function. One property of the density function is that it is one at its center
and monotonically decreases to zero at its outermost edge, which is called its radius of influence .