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EllipsoidalOccluder

EllipsoidalOccluder

new

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.

Parameters:
Name Type Argument 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:

Members

:Cartesian3

Gets or sets the position of the camera.

:Ellipsoid

Gets the occluding ellipsoid.

Methods

Determines whether or not a point, the occludee, is hidden from view by the occluder.

Parameters:
Name Type Description
occludee Cartesian3 The point to test for visibility.
Returns:
boolean 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

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.

Parameters:
Name Type Description
occludeeScaledSpacePosition Cartesian3 The point to test for visibility, represented in the scaled space.
Returns:
boolean 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

<static>

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.

Parameters:
Name Type Argument 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 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:
Cartesian3 The computed horizon culling point, expressed in the ellipsoid-scaled space.

<static>

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.

Parameters:
Name Type Argument 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:
Cartesian3 The computed horizon culling point, expressed in the ellipsoid-scaled space.

<static>

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.

Parameters:
Name Type Argument 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 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 <optional>
 3
center Cartesian3 <optional>
 Cartesian3.ZERO
result Cartesian3 <optional>
 The instance on which to store the result instead of allocating a new instance.
Returns:
Cartesian3 The computed horizon culling point, expressed in the ellipsoid-scaled space.