Terrain and sky disappear with camera height near zero

[pjcozzi]

Discussion, code example, and partial workaround: https://groups.google.com/forum/#!topic/cesium-dev/87rvANHNnjs

Terrain tiles are horizon culled (which also affects subsurface). The sky command is executed so the shader is most likely returning an alpha of zero.

[pjcozzi]

They start to disappear at about ~1 meter height.

[whalleyms]

Same problem here. In the geographic area where I am doing most of my simulation the undulation value is -31.99m and most of the terrain is at or near sea level. That means that the reported WGS84 altitude at MSL is -32. The problem above limits me to rendering scenes at altitudes above ~33m. Since I'm using Cesium as a graphics head for a helicopter simulation this is a real show-stopper.

[pjcozzi]

Also reported here: https://groups.google.com/forum/#!topic/cesium-dev/CQ_jovXcXsk

[WarpDrive]

Only relatively flat tiles disappear. https://groups.google.com/d/msg/cesium-dev/OON3DghJS-4/csZA-Q6pF5gJ

[pjcozzi]

CC #2415

[pjcozzi]

It's easy to reproduce this, by zooming to the "Dead Sea" and then zooming in a bit more.

[pjcozzi]

@bagnell can you look at this and #2415 in time for 1.14?

[pjcozzi]

@bagnell can you please reply to the Cesium forum threads in this issue, and let them know that this fix will be in Cesium 1.14 on October 1?