


Perlin NoisePerlin Noise, named after its inventor Ken Perlin, is a widely used texturing primitive in two and three dimensional image creation. The Perlin Noise function generates a smoothly interpolated space of pseudorandom values which can be used as the basis for the procedural generation of realistic natural textures, such as marble, clouds, grass and many others. This article demonstrates the Perlin Noise function in VB. A future article will look at using the output to generate natural textures. About Perlin NoiseThe best place to start to find out about the Perlin Noise function is this amusing presentation given by Ken Perlin, which walks through the history and description of the noise function, its uses and along the way some stunning images including a very furry "tribble". The fundamental algorithm is as follows:
A naive implementation of this algorithm has a high computational cost. Luckily, the algorithm has been investigated in terms of direct hardware implementation, which means many optimisations have been discovered. The implementation provided in this sample is a direct translation of Ken Perlin's Java Reference Implementation, published at http://mrl.nyu.edu/~perlin/noise/. If you take a look at it, you'll see that it includes the noise generation function and lookup tables to simplify each stage of the process. I would attempt to describe the function in detail, but find myself unworthy in the face of the leaps of imagination it must have taken to write this implementation, so I'll simply bow down and offer my respect! Note that one further optimisation which could be applied to this implementation is to inline the lerp and grad functions (although it is likely the improvement you'll get by doing that won't warrant the tedious difficulty of implementing it). Using Perlin NoiseThe demonstration application provides a class, cPerlin3D which contains the VB version of the code. The constructor for this class sets up the lookup table that is used to generate the noise function; then there is one function, Noise which returns the output value of the noise function for a particular coordinate in 3D space. The output value is a Double between 1 and 1, and the coordinates can be set to any value you want, as the noise function is continuous in 3D space. To demonstrate the output of the function, the sample application maps it onto a a DIB Section which is rendered onto screen. With each drawing step, the Z coordinate in 3D space is advanced, so each image is a slice through the 3D space represented by the function. Three parameters are provided to control the image that is generated:
ConclusionThis article provides an implementation of the Perlin Noise function in VB and demonstrates rendering the output to an image. Stay tuned for future articles which will look at how to use this to generate sky, marble and wood textures.


