The title describes the basic issue. We have two problems, the first is a source of the high quality 3D imagery, that the gEarth plugin provided. The 45° angle aerial data that both Google and Bing provide is adequate for our uses for now, but down the road we would like to upgrade to true 3D imagery that gEarth provided.
Secondly, we need a way to draw 3D objects over the top of that view, which we were able to do in gEarth using 3D KML.
Because we are hoping that Google will eventually provide access to the 3D views that gEarth once provided, our preference is develop using the gMaps API with their 45° aerial data for now with the idea that can update the '45° Aerial view' to 'Earth-view' at a later date.
We are looking at a variety of WebGL frameworks for the 3D drawing, my question is: can we use Cesium for this? It appears that we can use a variety of sources for imagery but I read also there appeared to be restrictions with Google's data.
the first is a source of the high quality 3D imagery, that the gEarth plugin provided
Cesium supports a number of standard tiled imagery formats such as TMS, WMS, OpenStreetMaps, etc. See the imagery layers tutorial for the full list. To see a few different imagery providers in Cesium, including Bing, check out the ones in the imagery selector in the top right of the basic Cesium Viewer.
I expect the selection and resolution to get better and better as time goes on given the data acquisition trends (cheaper and easier), for more info, check out a related talk we recently gave at MIT.
but down the road we would like to upgrade to true 3D imagery that gEarth provided
By 3D imagery, do you mean 3D buildings? This is on our roadmap, and we are in discussion with data providers. For example, see the attached screenshot of textured Honolulu buildings from CyberCity3D who use to provide 3D buildings for Google Earth.
we need a way to draw 3D objects over the top of that view, which we were able to do in gEarth using 3D KML.
For a list of 3D objects (geometries) that Cesium supports, check out this tutorial. Terrain-conforming vector data is also hot on our list and you can track progress in this issue: #2179.
What type of application are you working on? Can you share a link?
