Plant Simulation Based On Fractal Technology

As a new interdisciplinary, fractal geometry has received wide attention by the academia, since Mandelbrot proposed fractal concept in the 1970s. Fractal theory mainly describes the nature and nonlinear system objects which are not smooth and irregular, it also provides description language and theoretical basis for plant simulation. Natural plants have a wide variety, so their forms are varied, however, they mostly contain a same and self-similar physical structure rule: each independent part of form structure and the whole structure of plant possess highly similar characteristics. While fractal geometry is an important mathematical tool which can expresses this characteristics, and it provides a new concept and method for exploring the objective law and the inherent link of the complicated objects of the nature. Especially with the development of fractal theory, natural plant simulation is becoming an important research field of computer graphics. Plant simulation using fractal technology has already been one of the hot issues in modern times.In the first place, the creation and development history of fractal theory, the definition and the geometric characteristics of fractal as well as Hansdorff measurement and dimension are presented in the paper; and also plant simulation methods that are more commonly used are introduced briefly including L-System, IFS, Diffusion Limited Aggregation and Particle System. In the next place, this paper mainly aims at L-System and IFS, which is much more popular in the aspects of plant simulation, and makes an intensive study of the two plant simulation methods.In aspect of L–System: the basic principle, the classification and the algorithm design of L-System are introduced in this paper; by studying and improving the exsiting methods of the plant simulation based on L-System, the paper implements the thickness change of the trunk and branches with the level degree change. In order to make the trunk and branches which compose the plant more diverse in thickness, length, color and growth direction, flag variable and random function are added to the drawing parameters of L-System, and parameterized control of L-System are implemented, so it can make the integral form more natural and lifelike because of overcoming the deficiency of no difference of each level branches. Some work is also carried out in three-dimentional L-System using frustum of a cone to simulate the trunk and branches; by introducing the radius attenuation coefficient and the length of the attenuation coefficient,the natural characteristics of the branch that is thick at the bottom and thin at the top as well as shorter and thiner with the increase of the level are embodied, which makes three-dimentional L-System plant simulation more realistic.In aspect of IFS: the basic principle of IFS, the affine transformation,and implementation of the IFS algorithm are introduced. Adjusting the iterative probability by using random number generator, more varied plant form are embodied. The IFS algorithm in aspect of the drawing operation are studid and improved, and then the drawing line operation are midified to other graphics operation such as drawing circle, rectangle, triangle or combining of the two graphics; the method of plant simulation using IFS algorithm controlled by L-system are also studied and implented: the trunk and branches are simulated by L-System and the leaves are simulated by IFS algorithm, that is to say, the two methods are made together effectively, which can produces more natural and realistic simulation effect.At last, a thorough study has been carried out on dynamic changes in plant simulation. By making continuous changes on graphics parameters, some of the graphics parameters are continuously controlled, and then plant simulation that changes dynamically is implemented. As a result, fractal plants are generated more vividly and more in line with natural plants.