Creating Vegetation on a Large Scale

Shadows for 2D Trees
Creating realistic shadows for 2D trees can be quite challenging if not approached carefully. Even using a good approach can have dire consequences when specific details in implementation are not taken into consideration. There are four types of shadows that can be used in conjunction with 2D trees. Each has advantages and disadvantages and which method you use depends greatly on the same things discussed earlier, which also drive which type of vegetation you create; RAM, rendering time, scene complexity, etc. Though there is no official title to any of these shadows types, we will use the following terms to delineate the different types-

• 3D Shadows
• Opacity Mapped Shadows
• Project Light Shadows
• Image Shadows

3D Shadows
The most realistic type of shadow that can be used for a 2D tree is the shadow of a 3D tree. Unfortunately, it's also the least efficient and most time-consuming method. To implement, simply place a 3D tree at the center of a 2D tree, disable the Visible to Camera and Visible to Reflection options and disable the Cast Shadows option of the 2D tree. The images below show an example of a 2D tree using the shadow of a 3D tree. The 3D tree that was used was the Generic Oak from the 3ds Max Foliage feature. Even with the branches and trunk disabled, this particular tree can have from 5k to 8k faces, depending on which seed value you use. Although this is a relatively small number of faces for a scene of over a million faces, it would not be practical to use a large number of these trees to make 3D shadows because as few as 200 could add an additional one million faces to your scene.

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