Can I calculate forward/backward transformation from geolocation(lat/lon/height) to screen X,Y?

CesiumJS
1

Hi,

I want to know what geolocation point(lat/lon/height) is shown on the screen X,Y without user clicking event.
And also, want to know if each geolocation point is visible now or hidden behind the ridge.

Such calculation is possible?

2

Hi Ko-hei,

Yes! You can get the Cartesian3 (3D scene space position) from a given (x, y) pixel coordinates using Scene.pickPosition. Here’s some example code: http://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Picking.html&label=Showcases

Create a ray from your current camera position to the 3d point of interest, then use pick http://cesiumjs.org/Cesium/Build/Documentation/Globe.html?classFilter=globe#pick (which takes a ray) to return the first entity along that ray. If pick gives you the expected entity, then it’s visible. Otherwise, if its a different entity or undefined, it’s occluded.

Hope that helps!

  • Rachel
3

Hi Rachel,

Great! I will try, thank you!

Kohei

4

Hi Kohei,

The point to point visibility issue is a little more complicated than I described, so here’s a code example: http://cesiumjs.org/Cesium/Apps/Sandcastle/?src=Hello%20World.html&label=Showcases&gist=822f432f2955dc9d57dee6d42f3632a6

Let me know if you need any clarifications – hope that helps!

  • Rachel