camera.flyto -- preserve z value

CesiumJS
1

I'm trying to do a camera flyto but not change the z value. If I have a hard-coded z value, like this, I'm fine.

viewer.camera.flyTo({
          destination : Cesium.Cartesian3.fromDegrees( longitude, latitude, 10e6)
});

But what if I don't know what the current z value is, what do I use? I've tried viewer.camera.position.z, but the camera always zooms in noticeably if use that.

2

Thanks for posting your question and solution! I’m sure others in the community will find this thread helpful.

The flyTo does take a “maximumHeight” option, but if you want to just keep it at the height it currently is, setting the current camera height to the destination height is a good way to do this. So you could do:

// Get the camera height
var cameraHeight = camera.positionCartographic.height;
// Here position is a Cartesian3 of the camera destination

var cartographicDesination = Cesium.Cartographic.fromCartesian(position);

// Override its height
cartographicDesination.height = cameraHeight;
// Set it back to a Cartesian3, then fly to this destination

position = Cesium.Cartographic.toCartesian(cartographicDesination);

``

I’ve modified the 3D Tiles Interactivity Sandcastle to do this, here’s a link. If you select “Zoom to feature” and then right click anywhere, the camera will move to that building without changing its height.

3

I'm trying to do a camera flyto but not change the z value. If I have a hard-coded z value, like this, I'm fine.

viewer.camera.flyTo({
          destination : Cesium.Cartesian3.fromDegrees( longitude, latitude, 10e6)
});

But what if I don't know what the current z value is, what do I use? I've tried viewer.camera.position.z, but the camera always zooms in noticeably if use that.

--------

Firgured out the answer right before I posted this, so here it is for anyone else who needs to do this:

Use viewer.camera._positionCartographic.height for the z-value of the destination and you will preserve the z-value when you fly to the destination. I have not tested this extensively, so I don't know if this works when you change your orientation. My camera is looking straight down and the orientation is remaining constant.

4

It’s more obvious what this does in the original example:

https://cesiumjs.org/Cesium/Build/Apps/Sandcastle/?src=3D%20Tiles%20Interactivity.html

If you comment it out, you can see the camera will zoom right through the building, instead of stop a little before.

That’s a good catch with that little hop. This happens because flyTo tries to maintain a minimum distance to the ground. Setting the maximumHeight to the destination height should remove that.