It is virtual impossible to do this by hand with a modeling tool. Procedural techniques have been established for this problem. A small set of so called production rules define the topology and geometry of objects in a recursive way. Though they primarily were introduced to simulate the growth of plants by A. Lindenmayer and were extended by P. Prusinkiewicz for that purpose, they are also capable to generate a plenty of other objects that have a more or less repetitive structure. Beside plants objects like linear fractals, terrain, shells, crystals or even buildings belong to this class.
Productions specify how symbols are replaced in the current string.
In this way pL-systems produce a code that describes how geometric primitives are assembled to approximate a natural scene with sufficient detail. This is done before rendering. The code is then interpreted to obtain a geometric representation of the scene, which is necessary for the renderer. Thereby a huge number of linear transformations are applied to primitives, which puts them to the proper shape and position. This process is known as Turtle Graphics .