Procedural texture
A procedural texture is a computer-generated image created using an algorithm intended to create a realistic surface or volumetric representation of natural elements such as wood, marble, granite, metal, stone, and others, for use in texture mapping.
Usually, the natural look of the rendered result is achieved by the usage of fractal noise and turbulence functions. These functions are used as a numerical representation of the “randomness” found in nature.
Solid texturing is a process where the texture generating function is evaluated over at each visible surface point of the model. Traditionally these functions use Simplex noise or Perlin noise as their basis function, but some simple functions may use more trivial methods such as the sum of sinusoidal functions for instance. Solid textures are an alternative to the traditional 2D texture images which are applied to the surfaces of a model. It is a difficult and tedious task to get multiple 2D textures to form a consistent visual appearance on a model without it looking obviously tiled. Solid textures were created to specifically solve this problem.
Instead of editing images to fit a model, a function is used to evaluate the colour of the point being textured. Points are evaluated based on their 3D position, not their 2D surface position. Consequently, solid textures are unaffected by distortions of the surface parameter space, such as you might see near the poles of a sphere. Also, continuity between the surface parameterization of adjacent patches isn’t a concern either. Solid textures will remain consistent and have features of constant size regardless of distortions in the surface coordinate systems.
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