Growth simulation
Introduction
Vorest is a software or computer program in development designed by researchers from the Polytechnic University of Madrid Carlos Vilas Arias and Manuel Abellanas in 2007. It was created to emulate the evolution of forests. To simulate forest growth, this program is based on the Voronoi Diagram.
Description
The model used by the program is classified within the group of individual tree models (sigle-tree models), and is based on the fact that the growth of any tree can be explained based on the area of influence it occupies around it. This area of influence will increase or decrease depending on certain factors such as competition from surrounding trees, and can be appropriately modeled as a region in a weighted Voronoi Diagram. The calculation of generalized Voronoi Diagrams with weights (additive or multiplicative) or with different distance functions for each generator is a complicated task and in many cases expensive, from a computational point of view. In the case at hand, it is not the vertices or edges of the diagram that are interesting to know, but rather the area of their regions. For this reason and since the forestry application allows a certain tolerance in the calculation, the application does not carry out the exact calculation of Voronoi Diagrams. On the contrary, it focuses on the representation of these structures based on the visualization of the lower envelope of the distance functions to the generators, which by using the implemented tools can be done in a completely interactive manner. Once represented, it allows us to obtain the diagram obtained as the set of regions of influence of a series of studied trees. However, the usefulness of the application is not limited to the mere interactive visualization of the diagrams, but rather allows for a continuous simulation of the expected growth process for the trees loaded in the program. That is, starting from an initial given by the user (either from random data, manually generated data or real data loaded from an external file in HTML format), it is possible to advance in time, thus obtaining a prediction of the growth of the studied trees. The visual information offered by the application has two fundamental aspects.
Distance Function Editor
Firstly, it allows to represent the Voronoi Diagram that models the areas of influence of each of the trees loaded in the program, at the determined moment of their growth, being possible to use both predefined metrics of the application (Euclidean metric L-1, L-infinity) and distance functions defined by the user (by using the integrated editor of distance functions). On the other hand, it allows us to generate a more or less representation of the real appearance that could be expected of the trees studied in their natural environment, that is, the application is capable of generating a three-dimensional scene with a sufficiently high degree of detail (although in any case far from what we could consider a photorealistic level) of the appearance that the forest would present in reality. In this scene the user could use everything from textures to improve the appearance of the ground, to configuring the representation of a SkyBox, which allows a basic but effective three-dimensional background effect, all guided by a clear and simple interface of the application. It is important that users would not need specific computer knowledge to generate the appearance of each of the species they are going to work with. Vorest uses the free-use POV-Tree application to support the generation of forests. By using this application, three-dimensional POV-Ray maps can be generated that represent in a more or less realistic way the tree species studied by the user. The documentation on it is clear and abundant, and in any case its handling does not entail excessive complications, being simple and intuitive, and completely visual. Vorest greatly facilitates work with this type of three-dimensional Maya files, abstracting the user from the complexity that underlies their loading and manipulation, and allowing them to concentrate all their efforts on the process of defining species, adjusting the parameters of each one and defining in a completely visual way the color of the trunk and leaves, or the color with which dead trees of a given species would be represented. Finally, the application would allow the inclusion of a multitude of simultaneous species generated by the user in the simulation process.