AnalyticalGraphicsInc/cesium — pull request #557 by bagnell (2013-03-08 21:22:16+00:00)
Title: Fix Billboard.computeScreenSpacePosition.

`Billboard.computeScreenSpacePosition` was using the projection matrix and viewport transformation of the `UniformState`. The last primitive rendered and the number of frustums could cause the uniform to be in an unexpected state. The projection matrix would be that of the last frustum and the viewport transformation changed to be that of the last primitive's render state.