When use pickPosition, if it picks a primitive but not 3d tile, the position's altitude is too high.

1. A concise explanation of the problem you're experiencing.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

4. The Cesium version you're using, your operating system and browser.

I believe this was answered here:

https://github.com/AnalyticalGraphicsInc/cesium/issues/7628

See also this issue with some more tips, particular in Hannah’s last comment:

https://github.com/AnalyticalGraphicsInc/cesium/issues/7602

Let me know if that doesn’t answer your question!