EllipsoidalOccluder

new EllipsoidalOccluder(ellipsoid, cameraPosition)

Determine whether or not other objects are visible or hidden behind the visible horizon defined by an Ellipsoid and a camera position. The ellipsoid is assumed to be located at the origin of the coordinate system. This class uses the algorithm described in the Horizon Culling blog post.
Name Type Description
ellipsoid Ellipsoid The ellipsoid to use as an occluder.
cameraPosition Cartesian3 optional The coordinate of the viewer/camera. If this parameter is not specified, EllipsoidalOccluder#cameraPosition must be called before testing visibility.
Example:
// Construct an ellipsoidal occluder with radii 1.0, 1.1, and 0.9.
var cameraPosition = new Cesium.Cartesian3(5.0, 6.0, 7.0);
var occluderEllipsoid = new Cesium.Ellipsoid(1.0, 1.1, 0.9);
var occluder = new Cesium.EllipsoidalOccluder(occluderEllipsoid, cameraPosition);
Source: Core/EllipsoidalOccluder.js, line 41

Members

cameraPosition :Cartesian3

Gets or sets the position of the camera.
Source: Core/EllipsoidalOccluder.js, line 75

ellipsoid :Ellipsoid

Gets the occluding ellipsoid.
Source: Core/EllipsoidalOccluder.js, line 65

Methods

computeHorizonCullingPoint(directionToPoint, positions, result) → Cartesian3

Computes a point that can be used for horizon culling from a list of positions. If the point is below the horizon, all of the positions are guaranteed to be below the horizon as well. The returned point is expressed in the ellipsoid-scaled space and is suitable for use with EllipsoidalOccluder#isScaledSpacePointVisible.
Name Type Description
directionToPoint Cartesian3 The direction that the computed point will lie along. A reasonable direction to use is the direction from the center of the ellipsoid to the center of the bounding sphere computed from the positions. The direction need not be normalized.
positions Array.<Cartesian3> The positions from which to compute the horizon culling point. The positions must be expressed in a reference frame centered at the ellipsoid and aligned with the ellipsoid's axes.
result Cartesian3 optional The instance on which to store the result instead of allocating a new instance.
Returns:
The computed horizon culling point, expressed in the ellipsoid-scaled space.
Source: Core/EllipsoidalOccluder.js, line 156

computeHorizonCullingPointFromRectangle(rectangle, ellipsoid, result) → Cartesian3

Computes a point that can be used for horizon culling of an rectangle. If the point is below the horizon, the ellipsoid-conforming rectangle is guaranteed to be below the horizon as well. The returned point is expressed in the ellipsoid-scaled space and is suitable for use with EllipsoidalOccluder#isScaledSpacePointVisible.
Name Type Description
rectangle Rectangle The rectangle for which to compute the horizon culling point.
ellipsoid Ellipsoid The ellipsoid on which the rectangle is defined. This may be different from the ellipsoid used by this instance for occlusion testing.
result Cartesian3 optional The instance on which to store the result instead of allocating a new instance.
Returns:
The computed horizon culling point, expressed in the ellipsoid-scaled space.
Source: Core/EllipsoidalOccluder.js, line 251

computeHorizonCullingPointFromVertices(directionToPoint, vertices, stride, center, result) → Cartesian3

Computes a point that can be used for horizon culling from a list of positions. If the point is below the horizon, all of the positions are guaranteed to be below the horizon as well. The returned point is expressed in the ellipsoid-scaled space and is suitable for use with EllipsoidalOccluder#isScaledSpacePointVisible.
Name Type Default Description
directionToPoint Cartesian3 The direction that the computed point will lie along. A reasonable direction to use is the direction from the center of the ellipsoid to the center of the bounding sphere computed from the positions. The direction need not be normalized.
vertices Array.<Number> The vertices from which to compute the horizon culling point. The positions must be expressed in a reference frame centered at the ellipsoid and aligned with the ellipsoid's axes.
stride Number 3 optional
center Cartesian3 Cartesian3.ZERO optional
result Cartesian3 optional The instance on which to store the result instead of allocating a new instance.
Returns:
The computed horizon culling point, expressed in the ellipsoid-scaled space.
Source: Core/EllipsoidalOccluder.js, line 203

isPointVisible(occludee) → Boolean

Determines whether or not a point, the occludee, is hidden from view by the occluder.
Name Type Description
occludee Cartesian3 The point to test for visibility.
Returns:
true if the occludee is visible; otherwise false.
Example:
var cameraPosition = new Cesium.Cartesian3(0, 0, 2.5);
var ellipsoid = new Cesium.Ellipsoid(1.0, 1.1, 0.9);
var occluder = new Cesium.EllipsoidalOccluder(ellipsoid, cameraPosition);
var point = new Cesium.Cartesian3(0, -3, -3);
occluder.isPointVisible(point); //returns true
Source: Core/EllipsoidalOccluder.js, line 107

isScaledSpacePointVisible(occludeeScaledSpacePosition) → Boolean

Determines whether or not a point expressed in the ellipsoid scaled space, is hidden from view by the occluder. To transform a Cartesian X, Y, Z position in the coordinate system aligned with the ellipsoid into the scaled space, call Ellipsoid#transformPositionToScaledSpace.
Name Type Description
occludeeScaledSpacePosition Cartesian3 The point to test for visibility, represented in the scaled space.
Returns:
true if the occludee is visible; otherwise false.
Example:
var cameraPosition = new Cesium.Cartesian3(0, 0, 2.5);
var ellipsoid = new Cesium.Ellipsoid(1.0, 1.1, 0.9);
var occluder = new Cesium.EllipsoidalOccluder(ellipsoid, cameraPosition);
var point = new Cesium.Cartesian3(0, -3, -3);
var scaledSpacePoint = ellipsoid.transformPositionToScaledSpace(point);
occluder.isScaledSpacePointVisible(scaledSpacePoint); //returns true
Source: Core/EllipsoidalOccluder.js, line 129