Density Functions

The basic structure of participating media is defined by density functions $f(x)$ which return a scalar density value for each point $x$ in space. Different kinds of density functions exist. Procedural density functions are based on arithmetic expressions. Arbitrary expressions can be used - constant, linear, quadratic and so on, as well as turbulence, noise or other solid texturing functions. Excellent results can be achieved by using procedural density functions to render natural phenomena. Density functions may also be based on volume data sets, which are created by a large number of different methods and applications. Just to name a few: Computed Tomography (CT), Magnetic Resonance Imaging (MRI), finite elements simulations, sampled geological or meteorological quantities, ...