I was reading the Unity manual on trees and one of the claims made is as follows:
Unity uses optimisations (eg, billboarding for distant trees) to maintain good rendering performance...
I was planning on doing my own billboarding for a game I'm building anyway, so knowing that I'm going to gain a performance advantage is good to know. However, when I tried looking a little deeper at how billboarding is done in Unity, I found these sources:
http://wiki.unity3d.com/index.php?title=CameraFacingBillboard http://answers.unity3d.com/questions/20697/how-to-create-billboarding-planes.html http://answers.unity3d.com/questions/52656/how-i-can-create-an-sprite-that-always-look-at-the.html
Which all show that the way to do billboarding is to do a transform on the object each frame to make it face the camera. (I can't find much about billboarding in the official Unity documentation).
How does billboarding affect performance? Why would there be a performance boost if you have to transform "dense forests with thousands of trees" before each frame? Does unity have a native billboarding shader built in? If not, wouldn't billboarded sprites require, at the very least, the same amount of rendering power as other objects being drawn in a 3D scene?