Occluder

// Construct an occluder one unit away from the origin with a radius of one.
var cameraPosition = new Cartesian3.ZERO;
var occluderBoundingSphere = new BoundingSphere(new Cartesian3(0, 0, -1), 1);
var occluder = new Occluder(occluderBoundingSphere, cameraPosition);

Methods

getPosition

Returns the position of the occluder.

Returns:

Cartesian3 The position of the occluder.

getVisibility

Determine to what extent an occludee is visible (not visible, partially visible, or fully visible).

Parameters:

Name	Type	Description
occludeeBS	BoundingSphere	The bounding sphere of the occludee.

Throws:

DeveloperError : occludeeBS is required.

Returns:

Enumeration Visibility.NONE if the occludee is not visible, Visibility.PARTIAL if the occludee is partially visible, or Visibility.FULL if the occludee is fully visible.

Example

var sphere1 = new BoundingSphere(new Cartesian3(0, 0, -1.5), 0.5);
var sphere2 = new BoundingSphere(new Cartesian3(0, 0, -2.5), 0.5);
var cameraPosition = new Cartesian3(0, 0, 0);
var occluder = new Occluder(sphere1, cameraPosition);
occluder.getVisibility(sphere2); //returns Visibility.NONE

See:

• Occluder#isVisible

isBoundingSphereVisible

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

Parameters:

Name	Type	Description
occludee	BoundingSphere	The bounding sphere surrounding the occludee object.

Returns:

boolean true if the occludee is visible; otherwise false.

Example

var cameraPosition = new Cartesian3(0, 0, 0);
var littleSphere = new BoundingSphere(new Cartesian3(0, 0, -1), 0.25);
var occluder = new Occluder(littleSphere, cameraPosition);
var bigSphere = new BoundingSphere(new Cartesian3(0, 0, -3), 1);
occluder.isBoundingSphereVisible(bigSphere); //returns true

See:

• Occluder#getVisibility

isPointVisible

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

Parameters:

Name	Type	Description
occludee	Cartesian3	The point surrounding the occludee object.

Returns:

boolean true if the occludee is visible; otherwise false.

Example

var cameraPosition = new Cartesian3(0, 0, 0);
var littleSphere = new BoundingSphere(new Cartesian3(0, 0, -1), 0.25);
var occluder = new Occluder(littleSphere, cameraPosition);
var point = new Cartesian3(0, 0, -3);
occluder.isPointVisible(point); //returns true

See:

• Occluder#getVisibility

setCameraPosition

Sets the position of the camera.

Parameters:

Name	Type	Description
cameraPosition	Cartesian3	The new position of the camera.

Throws:

DeveloperError : cameraPosition is required.

<static> computeOccludeePointFromExtent

Computes a point that can be used as the occludee position to the visibility functions from an extent.

Parameters:

Name	Type	Argument	Default	Description
extent	Extent			The extent used to create a bounding sphere.
ellipsoid	Ellipsoid	<optional>	Ellipsoid.WGS84	The ellipsoid used to determine positions of the extent.

Throws:

DeveloperError : extent is required.

Returns:

Object An object containing two attributes: occludeePoint and valid which is a boolean value.

<static> fromBoundingSphere

Creates an occluder from a bounding sphere and the camera position.

Parameters:

Name	Type	Argument	Description
occluderBoundingSphere	BoundingSphere		The bounding sphere surrounding the occluder.
cameraPosition	Cartesian3		The coordinate of the viewer/camera.
result	Occluder	<optional>	The object onto which to store the result.

Throws:

• DeveloperError : occluderBoundingSphere is required.
• DeveloperError : cameraPosition is required.

Returns:

Occluder The occluder derived from an object's position and radius, as well as the camera position.

<static> getOccludeePoint

Computes a point that can be used as the occludee position to the visibility functions. Use a radius of zero for the occludee radius. Typically, a user computes a bounding sphere around an object that is used for visibility; however it is also possible to compute a point that if seen/not seen would also indicate if an object is visible/not visible. This function is better called for objects that do not move relative to the occluder and is large, such as a chunk of terrain. You are better off not calling this and using the object's bounding sphere for objects such as a satellite or ground vehicle.

Parameters:

Name	Type	Description
occluderBoundingSphere	BoundingSphere	The bounding sphere surrounding the occluder.
occludeePosition	Cartesian3	The point where the occludee (bounding sphere of radius 0) is located.
positions	Array	List of altitude points on the horizon near the surface of the occluder.

Throws:

• DeveloperError : positions is a required, non-empty array.
• DeveloperError : occluderBoundingSphere is required.
• DeveloperError : occludeePosition must have a value other than occluderBoundingSphere.center.

Returns:

Object An object containing two attributes: occludeePoint and valid which is a boolean value.

Example

var cameraPosition = new Cartesian3(0, 0, 0);
var occluderBoundingSphere = new BoundingSphere(new Cartesian3(0, 0, -8), 2);
var occluder = new Occluder(occluderBoundingSphere, cameraPosition);
var positions = [new Cartesian3(-0.25, 0, -5.3), new Cartesian3(0.25, 0, -5.3)];
var tileOccluderSphere = BoundingSphere.fromPoints(positions);
var occludeePosition = tileOccluderSphere.center;
var occludeePt = occluder.getOccludeePoint(occluderBoundingSphere, occludeePosition, positions);

<static> prototype.getRadius

Returns the radius of the occluder.

Returns:

Number The radius of the occluder.