Create a Forest

Creating a forest or something similar, with hundreds or possibly even thousands of items, can seem like a daunting task. However, thanks to Blender's particle system, it is actually pretty simple. Figure 1 shows a mountain I created using the ANT landscape generator, a nice Blender Add-On. ANT stands for Another Noise Tool, just in case you were wondering. So, I want to add a forest to my mountain, but I certainly don't want to spend a week populating it by hand. Particles to the rescue.

Figure 1

Figure 1 also shows the tree that I'm going to replicate across the mountain. This was made using Sapling, another terrific Add-On that is now part of the Blender standard builds. I've just given the tree basic colours, but of course you'd need to texture it and the mountain properly for a final render.

The first thing to do is to select the mountain and then create a Particle system for it. This is done simply by clicking on the Particles icon in the Properties window and selecting the + sign, as in Figure 2. Make sure Type is set to Emitter and not Hair. Note that all the following screenshots are of the various Particles panels.

Figure 2

Figure 3 shows the next panel down, the Emission panel. Amount is simply the number of trees, in this case 1000. Start and End should both be at 1, so that the particles (trees) remain static. Lifetime should be the length of your animation. If you go to the Render window in the Properties panel, there is a panel in there that has the Frame Range. In this case, the final frame is set to 250, so I set my particle lifetime to 250, so they don't disappear if I am animating. Emit from is set to Verts, or vertices. This means my trees will simply originate from various vertices on the model. Random should probably be ticked most of the time, because it gives, well, a nice randomness to the placement of the particles. De-selecting Random will order all the trees in rows.

Figure 3

Figure 4 shows the Rotation panel. Set this to None for objects like trees. You can experiment with the other settings in this panel. If you set the value to Normal, you'll end up with a flattened forest.

Figure 4

Figure 5 shows the Render panel. Emitter must be ticked, or the mountain won't render, as it is the emitter object. Make sure the Object button is selected, or the trees won't render. Dupli Object Tells Blender to use an object instead of particles. Click on the input box there and a pop-up menu will appear, as in Figure 5. Select the object that is going to be rendered. In this case of course, it's Tree. The Size value allows you to scale the object up or down, and the Random Size option, which in this screenshot is obscured by the drop-down menu, allows for random scaling of the objects. That's the basics. Figure 6 shows a render of the mountain covered in trees.

Figure 5

Figure 6

This technique can be used for all sorts of situations. You can use it to spread rubble around a scene, create a boulder field, spread flowers through a meadow, the list goes on. You do need to be careful about how many polygons the objects contain, because if you need a lot of them, your computer can quickly grind to a halt.