Perfect Vision
Compatibility with Perfect Vision should be much improved (issues #4 and #18). Added an additional non-radius vision shader and simplified the shader geometry calculation. This also addresses issue #15 in a more comprehensive way.
Fix for calculating averageElevationAtGridPoint.
Fix issue #19 (default elevation). Added a method, changePixelElevationValues, that changes every pixel that is currently at a specified elevation to a different elevation. Also added a macro for easy access to this functionality. This allows, for example, the user to change the scene from the default value to some other value.