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- = The Tree System
- :revnumber: 2.0
- :revdate: 2020/07/15
- Here you will learn how to use the tree system.
- == SimpleTreeTest.java
- There's a file in the demo-project named SimpleTreeTest. There's a method in it named *setupForester()* where you can see how a tree system is set up. If you haven't already done so, you might also want
- to check out the SimpleGrassTest.java file, because it contains a lot more information on certain other, important topics regarding the forester lib in general.
- The basic procedure is this:
- 1) Create a Forester object, and initialize it.
- 2) Use it to create a tree-loader.
- 3) Use the treeloader to create a map-provider.
- 4) Use the treeloader to create one tree-layer for each type of tree.
- 5) Tweak everything until it fits your app.
- 6) Make sure you call forester.update() each frame.
- == PhysicsTest.java
- There's another file in the demo project called PhysicsTest.java. In that file you can see how collision-shapes are added to the trees.
- When you create a tree-layer through *treeLoader.createTreeLayer(Spatial spat, boolean usePhysics)*, you supply the model and a boolean whether or not to use physics. If you want to enable collision physics, look in that file how it's done.
- There are some general principles:
- 1) In order to enable collision physics _at all_, you first need to set up a physics space. There's a great tutorial available in the tutorials section of the jME wiki: xref:tutorials:beginner/hello_physics.adoc[jme3:beginner:hello_physics].
- 2) If you want to enable physics with the forester, you need to provide the physics space to the Forester object. This is shown in the PhysicsTest.java file.
- 3) Once that is done, you need to provide a collision shape with your model, obviously. This can be done in several ways. You can do it through the jMP scene composer, or programmatically.
- When a model is supplied to a tree-layer, and physics is enabled, the model will be checked for collision shapes. The shape is then removed from the model, and added to the tree-layer instead.
- The reason for this is that the trees are lumped together in a process called geometry-batching. It is commonly used to reduce the number of drawing-calls for groups of objects that are very similar.
- What this means in practice is that your model is not just duplicated and spread out across the scene, they are in fact baked together into one single mesh (per "`block`"). This process is also used for collision shapes. They are all compounded into one large collision shape, then added to this newly created clump of vertices. Basically.
- *In short* - there are a couple of instances when the collision physics system may fail:
- - If you do not supply a physics space to the forester, no physics will be enabled.
- - If you do not check "`true`" for enable physics when creating the tree-layer.
- - If you do not supply a collision mesh to the model.
- == The tree data system (Basic)
- *Basics*
- At the core of tree placement is the class *TreeData*. It contains five floats representing a tree - x,y,z-coords, rotation, scale. This means a tree-layer just needs to keep one copy of the model, rather then many instances that differ only in transformation.
- Tree data is stored in TreeDataLists, which are basically arraylists.
- *Using tree data*
- In the SimpleTreeTest.java is an example of how to set up a treeloader to use density maps to generate tree-data through the *MapGrid* data-provider. You do not have to worry about this stuff if you use density maps.
- There will be info here on how to use the alternative *DataGrid* data-provider later.
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