/// <summary>
/// Create a vector that will draw one axis of the satellite's body axes.
/// </summary>
private static GraphicalVector CreateAxesVector(Platform platform, CartesianElement cartesianElement, Color color, string identifier)
{
var graphicalVector = new GraphicalVector
{
// Compute the vector for the given element in the satellite's body axes.
Vector = platform.OrientationAxes.GetVectorElement(cartesianElement),
// Specify the visual appearance of the vector.
VectorGraphics = new VectorGraphics
{
Length = 10.0,
Color = color,
},
LocationPoint = platform.LocationPoint,
};
// Set the identifier for the vector in the CZML document.
graphicalVector.Extensions.Add(new IdentifierExtension(identifier));
return(graphicalVector);
}
/// <summary>
/// Create a Platform for the requested satellite using a TLE for position.
/// The satellite will be visually represented by a labeled glTF model,
/// the satellite's orbit will be shown, and vectors will be drawn for
/// the body axes of the satellite, plus a vector indicating the direction
/// of the sun.
/// </summary>
private void CreateSatellite()
{
// Get the current TLE for the given satellite identifier.
var tleList = TwoLineElementSetHelper.GetTles(m_satelliteIdentifier, JulianDate.Now);
// Use the epoch of the first TLE, since the TLE may have been loaded from offline data.
m_epoch = tleList[0].Epoch;
// Propagate the TLE and use that as the satellite's location point.
var locationPoint = new Sgp4Propagator(tleList).CreatePoint();
m_satellite = new Platform
{
Name = "Satellite " + m_satelliteIdentifier,
LocationPoint = locationPoint,
// Orient the satellite using Vehicle Velocity Local Horizontal (VVLH) axes.
OrientationAxes = new AxesVehicleVelocityLocalHorizontal(m_earth.FixedFrame, locationPoint),
};
// Set the identifier for the satellite in the CZML document.
m_satellite.Extensions.Add(new IdentifierExtension(m_satelliteIdentifier));
// Configure a glTF model for the satellite.
m_satellite.Extensions.Add(new ModelGraphicsExtension(new ModelGraphics
{
// Link to a binary glTF file.
Model = new CesiumResource(GetModelUri("satellite.glb"), CesiumResourceBehavior.LinkTo),
// By default, Cesium plays all animations in the model simultaneously, which is not desirable.
RunAnimations = false,
}));
// Configure a label for the satellite.
m_satellite.Extensions.Add(new LabelGraphicsExtension(new LabelGraphics
{
// Use the name of the satellite as the text of the label.
Text = m_satellite.Name,
// Change the color of the label after 12 hours. This demonstrates specifying that
// a value varies over time using intervals.
FillColor = new TimeIntervalCollection <Color>
{
// Green for the first half day...
new TimeInterval <Color>(JulianDate.MinValue, m_epoch.AddDays(0.5), Color.Green, true, false),
// Red thereafter.
new TimeInterval <Color>(m_epoch.AddDays(0.5), JulianDate.MaxValue, Color.Red, false, true),
},
// Only show label when camera is far enough from the satellite,
// to avoid visually clashing with the model.
DistanceDisplayCondition = new Bounds(1000.0, double.MaxValue),
}));
// Configure graphical display of the orbital path of the satellite.
m_satellite.Extensions.Add(new PathGraphicsExtension(new PathGraphics
{
// Configure the visual appearance of the line.
Material = new PolylineOutlineMaterialGraphics
{
Color = Color.White,
OutlineWidth = 1.0,
OutlineColor = Color.Black,
},
Width = 2.0,
// Lead and Trail time indicate how much of the path to render.
LeadTime = Duration.FromMinutes(44.0).TotalSeconds,
TrailTime = Duration.FromMinutes(44.0).TotalSeconds,
}));
// Create vectors for the X, Y, and Z axes of the satellite.
m_satelliteXAxis = CreateAxesVector(m_satellite, CartesianElement.X, Color.Green, "SatelliteX");
m_satelliteYAxis = CreateAxesVector(m_satellite, CartesianElement.Y, Color.Red, "SatelliteY");
m_satelliteZAxis = CreateAxesVector(m_satellite, CartesianElement.Z, Color.Blue, "SatelliteZ");
// Create a vector from the satellite to the Sun.
// Compute the vector from the satellite's location to the Sun's center of mass.
var sunCenterOfMassPoint = CentralBodiesFacet.GetFromContext().Sun.CenterOfMassPoint;
var vectorSatelliteToSun = new VectorTrueDisplacement(m_satellite.LocationPoint, sunCenterOfMassPoint);
// Create the visual vector.
m_satelliteSunVector = new GraphicalVector
{
LocationPoint = m_satellite.LocationPoint,
Vector = vectorSatelliteToSun,
VectorGraphics = new VectorGraphics
{
Length = 5.0,
Color = Color.Yellow,
},
};
// Set the identifier for the vector in the CZML document.
m_satelliteSunVector.Extensions.Add(new IdentifierExtension("SunVector"));
// Orient the solar panels on the satellite model to point at the sun.
var satelliteYVector = m_satellite.OrientationAxes.GetVectorElement(CartesianElement.Y);
// allow only Z axis to rotate to follow sun vector. Constrain sun vector to Y, and satellite Y vector to X.
var constrainedAxes = new AxesAlignedConstrained(satelliteYVector, AxisIndicator.First, vectorSatelliteToSun, AxisIndicator.Second);
// Satellite axes are Vehicle Velocity Local Horizontal (VVLH) axes, where X is forward and Z is down,
// but Cesium model axes are Z forward, Y up. So, create an axes rotates to the Cesium model axes.
var offset = new UnitQuaternion(new ElementaryRotation(AxisIndicator.First, -Math.PI / 2)) *
new UnitQuaternion(new ElementaryRotation(AxisIndicator.Third, Math.PI / 2));
var cesiumModelAxes = new AxesFixedOffset(m_satellite.OrientationAxes, offset);
// The rotation will be from the Cesium model axes to the constrained axes.
var solarPanelRotationAxes = new AxesInAxes(constrainedAxes, cesiumModelAxes);
// Add a node transformation to rotate the SolarPanels node of the model.
m_satellite.Extensions.GetByType <ModelGraphicsExtension>().ModelGraphics.NodeTransformations = new Dictionary <string, NodeTransformationGraphics>
{
{
"SolarPanels", new NodeTransformationGraphics
{
Rotation = new AxesCesiumProperty(solarPanelRotationAxes)
}
}
};
}
