Added experimental osgTerrain::ShaderTerrain TerrainTechnique to osgterrain example to flesh out new shader based displacement mapping approach to osgTerrain databases.

Requires shader files place in OpenSceneGraph-Data/shaders from OpenSceneGraph-Data's svn/trunk to function.

Run osgterrain example with --shader command line option to select displacement mapping shader approach.



git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14458 16af8721-9629-0410-8352-f15c8da7e697