Vegetation
GenesisII draws vegetation in 3D using LSystem models. Any number of plants may be defined.

An LSystem is a rule like description of a 3d form. Rules are defined in plain text in a .ls files which and simply contain descriptions of parts and how they should be assembled together. We use the syntax defined by Laurens LaprΘ for his LParser system (http://www.xs4all.net/~ljlapre/) and you can use any of the tools or files available from his website to define plants for GenesisII. We particularly recommend the freeware LParser editor created by Bryan Smith and available at http://www.thinkpiece.com/downloads/lsystem.asp for creating files.

Vegetation Editor

Plants

Plant list: List the plants available. Click New to add a plant. Select a plant to edit it's properties.

Properties

• Name: An arbitrary name assigned to each plant. Does not have to be unique - although this is recommended.
• Source Files: LSystem ls files containing the plant definition. You need to define 3 files for each plant corresponding to the level of detail that should be drawn for objects in the far distance, middle ground and nearby. We supply example sets for 'conifer' and 'oak' trees with the GenesisII download and more are available from our site. See the notes below for more discussion of this.
• Set Vegetation Directory: Sets directory path for vegetation LSystem files.
• Colors: The LSystem file definition uses a set of 16 colors that can be used to drawn the model. We supply the 'standard' LParser defaults but you may edit these as you wish (to produce an autumnal or winter scene perhaps). Color sets may be saved and loaded.

Some Notes

An L-System is a rule like description of a 3d form. It contains descriptions of parts and how they should be assembled together. The description is applied to itself a number of times (= recursion levels) so fractal and recursive forms are very easy to describe in an L-system. That's why they are used a lot for plants and natural looking organic forms. By increasing the recursion level the form slowly 'grows' and becomes more complex.

It is not necessary to understand the details of how an LSystem object is defined to use vegetation in GenesisII - we include some sample files with the download and additional selections are available from our website which you can just plug these directly into the program. However LSystems are fascinating to experiment with and we highly recommend downloading files from Laurens LaprΘ's site. GenesisII can render any LParser file that defines the object in polygons only - i.e. user-defined shapes such as blobs are not allowed. In practise this is not a significant restriction for our purposes.

If you define your own LSystem files you should also ensire that the file definition includes some randomness else you will create a forest of identical trees. The sample files include with GenesisII are examples of this technique.

Finally, why do we require you to define 3 files for each plant? (at far, mid and near resolution). Well, we've always believed that GenesisII should be an 'Open' system that can use and incorporate material defined outside itself as much as possible. As landscapes can contain a lot of vegetation it is necessary to use simpler models for more distant plants if render times are to be kept to realistic values. However with an LSystem simplifying the model is not always straightforward (for example reducing the number of generations for instance might give you just a tree trunk and no leaves rather than a simpler tree) and programming this in automatically would impose greater restrictions on the types of models that can be used. Rather than do this we ask you to perform this step and not compromise flexibility.