3D graphics eBook - Course Materials Repository

Procedural texture 121
Procedural texture
A procedural texture is a computer generated image created
using an algorithm intended to create a realistic
representation of natural elements such as wood, marble,
granite, metal, stone, and others.
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
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 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
A procedural floor grate texture generated with the texture
editor Genetica [1] .
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. [2]
Cellular texturing
Cellular texturing differs from the majority of other procedural texture generating techniques as it does not depend
on noise functions as its basis, although it is often used to complement the technique. Cellular textures are based on
feature points which are scattered over a three dimensional space. These points are then used to split up the space
into small, randomly tiled regions called cells. These cells often look like “lizard scales,” “pebbles,” or “flagstones”.
Even though these regions are discrete, the cellular basis function itself is continuous and can be evaluated anywhere
in space. [3]
Genetic textures
Genetic texture generation is highly experimental approach for generating textures. It is a highly automated process
that uses a human to completely moderate the eventual outcome. The flow of control usually has a computer
generate a set of texture candidates. From these, a user picks a selection. The computer then generates another set of
textures by mutating and crossing over elements of the user selected textures [4] . For more information on exactly
how this mutation and cross over generation method is achieved, see Genetic algorithm. The process continues until
a suitable texture for the user is generated. This isn't a commonly used method of generating textures as it’s very
difficult to control and direct the eventual outcome. Because of this, it is typically used for experimentation or
abstract textures only.