Earth-centered view in ICRF frame

[emackey]

There should be a way to get a view similar to the Home view, centered on the Earth, in the ICRF frame instead of Earth-fixed.

[mramato]

The code to do this is actually trivial (see the below snippet). But I'm not sure how we would implement it in widget form (because it's not a one-off thing and depends on state). It's also highly specific to space-based visualization, so I'm not sure the majority of people would care. It's certainly something Cesium Viewer will be able to do at some point, but the new Viewer widget will probably not. It's also probably going to be part of a larger system and not just a click button for "inertial view". That being said, I'm just thinking out loud and open for ideas.

//Put this in an onTick callback and execute every frame.
var mode = this.scene.mode;
var camera = this.scene.getCamera();
if (mode === SceneMode.SCENE3D) {
  this.icrfTransform = Transforms.computeIcrfToFixedMatrix(currentTime, this.icrfTransform);
  if (typeof this.icrfTransform !== 'undefined') {
      Matrix4.fromRotationTranslation(this.icrfTransform, Cartesian3.ZERO, camera.transform);
  }
}

[pjcozzi]

This is also in the Camera Sandcastle example now.

https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Apps/Sandcastle/gallery/Camera.html#L150

Should we close this?

[emackey]

Stored views depend on this. The code examples above have the 1 frame lag bug on the selectionIndicator.

[mramato]

There are also bugs in the sandcastle example (panning the mouse for instance). The only "real" way to add ICRF support is to build it into the camera itself. We had some discussion of this in #1789. I would leave this open until we have complete out of the box support.