Transforms

Contains functions for transforming positions to various reference frames.

Source:

/Source/Core/Transforms.js

Members

<static> earthOrientationParameters :EarthOrientationParameters

The source of Earth Orientation Parameters (EOP) data, used for computing the transformation between the Fixed and ICRF axes. By default, zero values are used for all EOP values, yielding a reasonable but not completely accurate representation of the ICRF axes.

See:

<static> iau2006XysData :Iau2006XysData

The source of IAU 2006 XYS data, used for computing the transformation between the Fixed and ICRF axes.

See:

Methods

<static> computeFixedToIcrfMatrix

Computes a rotation matrix to transform a point or vector from the Earth-Fixed frame axes (ITRF) to the International Celestial Reference Frame (GCRF/ICRF) inertial frame axes at a given time. This function may return undefined if the data necessary to do the transformation is not yet loaded.

Parameters:

Name	Type	Argument	Description
`date`	JulianDate		The time at which to compute the rotation matrix.
`result`	Matrix3	<optional>	The object onto which to store the result. If this parameter is not specified, a new instance is created and returned.

Throws:

DeveloperError : date is required.

Returns:

Matrix3 The rotation matrix, or undefined if the data necessary to do the transformation is not yet loaded.

Example

// Transform a point from the ICRF axes to the Fixed axes.
var now = new JulianDate();
var pointInFixed = new Cartesian3(...);
var fixedToIcrf = Transforms.computeIcrfToFixedMatrix(now);
var pointInInertial;
if (typeof fixedToIcrf !== 'undefined') {
    pointInInertial = fixedToIcrf.multiplyByVector(pointInFixed);
}

See:

Transforms.preloadIcrfFixed

<static> computeIcrfToFixedMatrix

Computes a rotation matrix to transform a point or vector from the International Celestial Reference Frame (GCRF/ICRF) inertial frame axes to the Earth-Fixed frame axes (ITRF) at a given time. This function may return undefined if the data necessary to do the transformation is not yet loaded.

Parameters:

Name	Type	Argument	Description
`date`	JulianDate		The time at which to compute the rotation matrix.
`result`	Matrix3	<optional>	The object onto which to store the result. If this parameter is not specified, a new instance is created and returned.

Throws:

DeveloperError : date is required.

Returns:

Matrix3 The rotation matrix, or undefined if the data necessary to do the transformation is not yet loaded.

Example

//Set the view to the inertial frame.
function updateAndRender() {
    var now = new JulianDate();
    scene.initializeFrame();
    scene.setSunPosition(Simon1994PlanetaryPositions.ComputeSunPositionInEarthInertialFrame(now));
    var icrfToFixed = Transforms.computeIcrfToFixedMatrix(now);
    if (typeof icrfToFixed !== 'undefined') {
        scene.getCamera().transform = Matrix4.fromRotationTranslation(icrfToFixed, Cartesian3.ZERO);
    }
    scene.render();
    requestAnimationFrame(updateAndRender);
}
updateAndRender();

See:

Transforms.preloadIcrfFixed

<static> computeTemeToPseudoFixedMatrix

Computes a rotation matrix to transform a point or vector from True Equator Mean Equinox (TEME) axes to the pseudo-fixed axes at a given time. This method treats the UT1 time standard as equivalent to UTC.

Parameters:

Name	Type	Argument	Description
`date`	JulianDate		The time at which to compute the rotation matrix.
`result`	Matrix3	<optional>	The object onto which to store the result.

Throws:

DeveloperError : date is required.

Returns:

Matrix3 The modified result parameter or a new Matrix3 instance if none was provided.

Example

//Set the view to in the inertial frame.
function updateAndRender() {
    var now = new JulianDate();
    scene.initializeFrame();
    scene.setSunPosition(Simon1994PlanetaryPositions.ComputeSunPositionInEarthInertialFrame(now));
    scene.getCamera().transform = Matrix4.fromRotationTranslation(Transforms.computeTemeToPseudoFixedMatrix(now), Cartesian3.ZERO);
    scene.render();
    requestAnimationFrame(updateAndRender);
}
updateAndRender();

<static> eastNorthUpToFixedFrame

Computes a 4x4 transformation matrix from a reference frame with an east-north-up axes centered at the provided origin to the provided ellipsoid's fixed reference frame. The local axes are defined as:

The x axis points in the local east direction.
The y axis points in the local north direction.
The z axis points in the direction of the ellipsoid surface normal which passes through the position.

Parameters:

Name	Type	Argument	Default	Description
`origin`	Cartesian3			The center point of the local reference frame.
`ellipsoid`	Ellipsoid	<optional>	Ellipsoid.WGS84	The ellipsoid whose fixed frame is used in the transformation.
`result`	Matrix4	<optional>		The object onto which to store the result.

Throws:

DeveloperError : origin is required.

Returns:

Matrix4 The modified result parameter or a new Matrix4 instance if none was provided.

Example

// Get the transform from local east-north-up at cartographic (0.0, 0.0) to Earth's fixed frame.
var ellipsoid = Ellipsoid.WGS84;
var center = ellipsoid.cartographicToCartesian(Cartographic.ZERO);
var transform = Transforms.eastNorthUpToFixedFrame(center);

<static> northEastDownToFixedFrame

Computes a 4x4 transformation matrix from a reference frame with an north-east-down axes centered at the provided origin to the provided ellipsoid's fixed reference frame. The local axes are defined as:

The x axis points in the local north direction.
The y axis points in the local east direction.
The z axis points in the opposite direction of the ellipsoid surface normal which passes through the position.

Parameters:

Name	Type	Argument	Default	Description
`origin`	Cartesian3			The center point of the local reference frame.
`ellipsoid`	Ellipsoid	<optional>	Ellipsoid.WGS84	The ellipsoid whose fixed frame is used in the transformation.
`result`	Matrix4	<optional>		The object onto which to store the result.

Throws:

DeveloperError : origin is required.

Returns:

Matrix4 The modified result parameter or a new Matrix4 instance if none was provided.

Example

// Get the transform from local north-east-down at cartographic (0.0, 0.0) to Earth's fixed frame.
var ellipsoid = Ellipsoid.WGS84;
var center = ellipsoid.cartographicToCartesian(Cartographic.ZERO);
var transform = Transforms.northEastDownToFixedFrame(center);

<static> pointToWindowCoordinates

Transform a point from model coordinates to window coordinates.

Parameters:

Name	Type	Argument	Description
`modelViewProjectionMatrix`	Matrix4		The 4x4 model-view-projection matrix.
`viewportTransformation`	Matrix4		The 4x4 viewport transformation.
`point`	Cartesian3		The point to transform.
`result`	Cartesian2	<optional>	The object onto which to store the result.

Throws:

DeveloperError : modelViewProjectionMatrix is required.
DeveloperError : viewportTransformation is required.
DeveloperError : point is required.

Returns:

Cartesian2 The modified result parameter or a new Cartesian2 instance if none was provided.

See:

<static> preloadIcrfFixed

Preloads the data necessary to transform between the ICRF and Fixed axes, in either direction, over a given interval. This function returns a promise that, when resolved, indicates that the preload has completed.

Parameters:

Name	Type	Description
`timeInterval`	TimeInterval	The interval to preload.

Returns:

Promise A promise that, when resolved, indicates that the preload has completed and evaluation of the transformation between the fixed and ICRF axes will no longer return undefined for a time inside the interval.

Example

var interval = new TimeInterval(...);
when(preloadIcrfFixed(interval), function() {
    // the data is now loaded
});