CZML Multiple Ellipses and CZML Ellipsoid

Hello there,

I have two questions,

1. - Is it possible to create two objects of the same type from CZML? If I want to define multiple ellipses from CZML, is this possible?

The following is a snippet of CZML code that is used to create and display an ellipse (this is within the CZML that defines a vehicle so it will follow its position). This works fine for a single ellipse, but if I were to try to create a second ellipse this way, errors are thrown for having the same property twice (ellipse).

"ellipse" :
{
    "bearing" :
    {
        "epoch" : "2012-08-04T16:00:00Z",
        "number" : [0, 0, 3894.996219574019, 6.28318531]
    },
    "semiMajorAxis" :
    {
        "epoch" : "2012-08-04T16:00:00Z",
        "number" : [0, 30000, 3894.996219574019, 10000]
    },
    "semiMinorAxis" :
    {
        "epoch" : "2012-08-04T16:00:00Z",
        "number" : [0, 10000, 3894.996219574019, 30000]
    }
},
"polyline" :
{
    "color" :
    [{
        "interval" : "2012-08-04T16:00:00Z/2012-08-04T18:00:00Z",
        "rgba" : [255, 255, 0, 255]
    }]
},
"polygon" :
{
    "color" :
    [{
        "interval" : "2012-08-04T16:00:00Z/2012-08-04T18:00:00Z",
        "rgba" : [255, 255, 0, 255]
    }]
}

2.- Displaying an ellipsoid via CZML.

I am using the following in CZML to try to display an ellipsoid that follows a vehicle in the same way that the ellipse would. Note: The Position property is defined for the vehicle, but the "Orientation" property is not. I am under the impression that the "Orientation" property only affects geometry and not the actual vehicle. Is this required to display the ellipsoid? And if so, how is the "Orientation" property implemented? The documentation for the "axes" and "unitQuaternion" are TODO's. https://github.com/AnalyticalGraphicsInc/cesium/wiki/CZML-Content

"ellipsoid" :
{
    "show" :
    [{
        "interval" : "2012-08-04T16:00:00Z/2012-08-04T18:00:00Z",
                            "boolean" : true
    }],
    "radii" :
    {
        "cartesian" : [40000, 40000, 40000]
    },
    "material" :
    {
        "solidColor" :
        {
            "color" :
            {
                "rgba" : [255, 255, 0, 255]
            }
        }
    }
},

Sorry for the delayed reply.

  1. The answer to your first question is, not yet but we are thinking about it. So while you can have a polyline and ellipsoid on a single object ID, you can’t currently have two ellipsoids on a single object.

  2. Orientation is required for Ellipsoids because they are represented in 3D space. I’m no expert on Quaternions, but I did fine this slide-deck on them that you might find useful: http://graphics.ucsd.edu/courses/cse169_w05/CSE169_04.ppt There’s also an ancient Gamasutra article on them: http://www.gamasutra.com/view/feature/3278/ I think we will eventually offer some easier ways to define orientation (Euler Angles/Yaw-Pitch-Roll/etc…) but these representations have issues when it comes to interpolation. I’ll write up an issue so we revisit the topic in the near future.

Matt -

Apologize for the bump on an old thread; but has the stance on multiple instances of one type of primitive on a single entity changed?

For example, I would ideally specify an array of EllipseGeometries against a single Entity. I haven’t seen any concrete examples of anyone doing so and my experiments have not been successful, so I figure this is still the case but wanted to double-check. :slight_smile:

Thank you.

  • Chris

Hello Chris,

Sorry, the Entity API doesn’t support that kind of behavior.

-Hanah