GeoPositionInterpolator node

This implements the GeoPositionInterpolator node. The geovalue_changed output field contains the interpolated geo-coordinates. The value_changed output field provides scene coordinates. Scene coordinates are geocentric coordinates adjusted for a GeoOrigin when provided. The node introduces an additional SFBool field called "onGreatCircle". It lets a user choose between linear and great circle type interpolation. Great circles give the shortest path between two points on the globe. The onGreatCircle field is set to false by default for performance and compatibility reasons. This means by default the node will use linear interpolation to interpolate between coordinates. At small distances a great circle is closely approximated by a straight line but at larger angular distances there is a significant difference.

Here is an example which is based on http://www.web3d.org/x3d/content/examples/Basic/Geospatial/A2_AnimatedGeoViewpoint.x3d and exercises most of the functionality of the node:

https://googledrive.com/host/0BwIhFzkLaQ9XeDJmV2JMRU9uSkU/A2_AnimatedGeoViewpoint_vAP.html

Also see discussion on mailing list.