I'm trying to draw polyline in Cesium 3D model and the terrain is used by STK world terrain meshes. When I want to draw the outline of a building, the specified position and the displaying position are different (the reference image: http://i.imgur.com/Zd6yY2c.png, I click the corner of this building but the polyline is outer). I think the reason is the response place which I clicked is on the ellipsoid, not on the terrain. So my problem is, could the specified position be coincided with the displaying position? And how could I do if the answer is positive? Thanks a lot~
Polylines on terrain is on our roadmap, but there is still a lot of research to be done.
Meanwhile, you could try to query the terrain provider for the position with the correct height using the sampleTerrain function. You provide the function with an array of Cartographic points, and it returns a promise to an array of those points with an adjusted height. This example demonstrates how to use that function: http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Terrain.html&label=Showcases
Scroll to the bottom where it says ‘Sample Everest Terrain’
