Thanks Scott. Let me answer in-line:
Currently, Cesium generally supports a single central body in a scene
(the scene's "globe").
And how could I tell it to be Venus, Neptune or whatever other body?
By changing the ellipsoid parameters (i.e. using a custom Ellipsoid
object), as I mentioned in my previous email, to change the shape of the
You could even turn off the globe visually, and then consider the reference
frame of the scene as the solar system barycenter and position ellipsoids
in that coordinate system.
Other bodies can be rendered using an EllipsoidPrimitive (as done with the
Moon) or as a custom billboard (as done with the Sun),
What do you mean by "as done with the Moon" or "with the Sun"? Do you have
specific examples at hand?
The Moon and Sun are rendered by default in the Cesium scene, in their
correct locations. (there's a Vectors sandcastle example that can help
find their location in the sky to see what they look like)
You can look in their source files to see how they are implemented.
The Moon is simpler, a basic textured ellipsoid. The Sun uses a custom
shader to get the visual flare effect.
You're right that CZML doesn't specify the body that data is defined in,
but generally it is all loaded relative to the scene's body, which defines
the reference frame for cartesian coordinates specified in the CZML file.
So if I understood correctly, given a CZML there's no way to know which
body it originated from. Is that correct? Perhaps there is some metadata
that I can use for that? Even some simple parameters like the gravitational
parameter or the radius would suffice.
CZML supports custom properties, which you could use to include whatever
value of those properties and reconfigure the display accordingly.