I’ve been digging around through Cesium source, docs, and group posts to get a better grasp on how to implement various application requirements based on Cesium’s current features. I’ve previously implemented things using Google Earth, so I’ve been trying to put together a mental mapping of GE concepts to Cesium concepts.
There’s two particular scenarios that I’m not sure about at the moment. The first is being able to define altitudes in terms of “AGL” (“Above Ground Level”). The GE equivalent would be AltitudeMode.ALTITUDE_RELATIVE_TO_GROUND. Looking at the Cesium.Cartographic class, the “height” parameter is defined as “The height, in meters, above the ellipsoid.” I interpret that to be equivalent to MSL (“Mean Sea Level” / AltitudeMode.ABSOLUTE). Am I correct that Cesium does not have any particular support for AGL altitudes right now? (I’m assuming not, especially since terrain support was just added.) I’m particularly looking to be able to show billboards and polylines whose positions are automatically rendered appropriately above terrain. It’d be great if the polylines would automatically flow up and over the terrain mid-segment, but I’d settle for just having the specifically-entered points be rendered at the right places.
The other related thing I’m looking to do is query Cesium about terrain elevation at a given lat/lon. I see a previous discussion from earlier this month that says some people have put something together, but no indication that that feature has made it into Cesium’s source yet. Anyone know if that ability is coming soon?