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January 2010 Viewpoint n n n n random patterns, dirt, sand, grass, clouds, or grains have some dis- tinct structure to them, we need to be able to produce the matching procedural texture of similar-sized random features. e first solution to this problem was proposed by Ken Perlin as early as 1983, just about the time when the movie Tron was released. Later, in 1997, Perlin received a Technical Achievement Award from the Academy of Motion Picture Arts and Sciences for his contributions to pro- cedural noise textures. Variations of so-called Perlin Noise are still commonly used; they are easy to control for artists and are able to produce realistic aesthetics. (For further information on Perlin Noise, v isit When computing pseudo-random signals, we always start with an initial seed number. is single value—and the production steps, of course—completely determine the whole sequence. Is this a problem for us? Not at all! One benefit is the minimal memory requirement to store such random textures, regardless of resolution. e other critical aspect is repeatability. Imagine that we create a complex particle simula- tion with a turbulent dynamic field driven by a 3D noise texture. If the signal were truly random, we would have to save the complete simula- tion to disk, as the final sequence would look different each time we ran it. However, by initializing the noise generation with the same seed number, it is guaranteed that the virtual leaves blown by our turbulent wind will move the same each time we run the sim. But what if the client picks up on a single particle moving in a strange way? We can simply enter a different seed number and have a brand-new simulation with a turbulence of similar "statistical" properties. While photographed dirt textures are images that need to be mapped into the surface of 3D models, the basis of the Perlin (and almost all other) noise is a pseudo-random signal that fills the 3D space. Using 3D, or volumetric procedural textures, we can completely avoid texture mapping as each point of the surface is mapped to a texture coordinate, without introducing any mapping artifacts. It is like inserting the ob- ject into a 3D cloud of noise and slicing out the final texture with the surfaces: ere will not be any seams or areas of different resolution. Another key property of Perlin Noise is that the sizes of the random variations are roughly the same. While a single layer of the texture may appear a bit too uniform, combining several layers, or octaves, of vari- ous characteristic sizes results in a very rich, realistic look. In doing this, we maintain complete control over the frequencies in the deterministic random signal. n High�Performance CameraTracking Use SynthEyes for animated critter insertion,»xing shaky shots, virtual set extensions, making 3D movies, architectural previews, accident reconstruction, virtual product placement, face and body capture, and more. 32-bitonly�$399 Windows-32�/Windows-64�/�OSX-32/OS�X-64 See the website for details of the latest version! Perlin Noise textures of one, two, and four octaves are used to displace the surface of the spheres.

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