Class: PerspectiveOffCenterFrustum

PerspectiveOffCenterFrustum

new PerspectiveOffCenterFrustum(options)

The viewing frustum is defined by 6 planes. Each plane is represented by a Cartesian4 object, where the x, y, and z components define the unit vector normal to the plane, and the w component is the distance of the plane from the origin/camera position.

Name Type Description
options Object 可选

An object with the following properties:

Name Type Default Description
left Number 可选

The left clipping plane distance.
right Number 可选

The right clipping plane distance.
top Number 可选

The top clipping plane distance.
bottom Number 可选

The bottom clipping plane distance.
near Number 1.0 可选

The near clipping plane distance.
far Number 500000000.0 可选

The far clipping plane distance.
See:
Example
var frustum = new SuperMap3D.PerspectiveOffCenterFrustum({
    left : -1.0,
    right : 1.0,
    top : 1.0,
    bottom : -1.0,
    near : 1.0,
    far : 100.0
});

Members

bottomNumber

Defines the bottom clipping plane.

Default Value:
undefined

farNumber

The distance of the far plane.

Default Value:
500000000.0

readonly infiniteProjectionMatrixMatrix4

Gets the perspective projection matrix computed from the view frustum with an infinite far plane.

See:

leftNumber

Defines the left clipping plane.

Default Value:
undefined

nearNumber

The distance of the near plane.

Default Value:
1.0

readonly projectionMatrixMatrix4

Gets the perspective projection matrix computed from the view frustum.

See:

Defines the right clipping plane.

Default Value:
undefined

topNumber

Defines the top clipping plane.

Default Value:
undefined

Methods

clone(result){PerspectiveOffCenterFrustum}

Returns a duplicate of a PerspectiveOffCenterFrustum instance.

Name Type Description
result PerspectiveOffCenterFrustum 可选

The object onto which to store the result.
Returns:
Type Description
PerspectiveOffCenterFrustum The modified result parameter or a new PerspectiveFrustum instance if one was not provided.

computeCullingVolume(position, direction, up){CullingVolume}

Creates a culling volume for this frustum.

Name Type Description
position Cartesian3

The eye position.
direction Cartesian3

The view direction.
up Cartesian3

The up direction.
Returns:
Type Description
CullingVolume A culling volume at the given position and orientation.
Example
// Check if a bounding volume intersects the frustum.
var cullingVolume = frustum.computeCullingVolume(cameraPosition, cameraDirection, cameraUp);
var intersect = cullingVolume.computeVisibility(boundingVolume);

equals(other){Boolean}

Compares the provided PerspectiveOffCenterFrustum componentwise and returns true if they are equal, false otherwise.

Name Type Description
other PerspectiveOffCenterFrustum 可选

The right hand side PerspectiveOffCenterFrustum.
Returns:
Type Description
Boolean true if they are equal, false otherwise.

equalsEpsilon(other, relativeEpsilon, absoluteEpsilon){Boolean}

Compares the provided PerspectiveOffCenterFrustum componentwise and returns true if they pass an absolute or relative tolerance test, false otherwise.

Name Type Default Description
other PerspectiveOffCenterFrustum

The right hand side PerspectiveOffCenterFrustum.
relativeEpsilon Number

The relative epsilon tolerance to use for equality testing.
absoluteEpsilon Number relativeEpsilon 可选

The absolute epsilon tolerance to use for equality testing.
Returns:
Type Description
Boolean true if this and other are within the provided epsilon, false otherwise.

getPixelDimensions(drawingBufferWidth, drawingBufferHeight, distance, pixelRatio, result){Cartesian2}

Returns the pixel's width and height in meters.

Name Type Description
drawingBufferWidth Number

The width of the drawing buffer.
drawingBufferHeight Number

The height of the drawing buffer.
distance Number

The distance to the near plane in meters.
pixelRatio Number

The scaling factor from pixel space to coordinate space.
result Cartesian2

The object onto which to store the result.
Throws:

  • drawingBufferWidth must be greater than zero.

    Type
    DeveloperError

  • drawingBufferHeight must be greater than zero.

    Type
    DeveloperError

  • pixelRatio must be greater than zero.

    Type
    DeveloperError
Returns:
Type Description
Cartesian2 The modified result parameter or a new instance of Cartesian2 with the pixel's width and height in the x and y properties, respectively.
Examples
// Example 1
// Get the width and height of a pixel.
var pixelSize = camera.frustum.getPixelDimensions(scene.drawingBufferWidth, scene.drawingBufferHeight, 1.0, scene.pixelRatio, new SuperMap3D.Cartesian2());
// Example 2
// Get the width and height of a pixel if the near plane was set to 'distance'.
// For example, get the size of a pixel of an image on a billboard.
var position = camera.position;
var direction = camera.direction;
var toCenter = SuperMap3D.Cartesian3.subtract(primitive.boundingVolume.center, position, new SuperMap3D.Cartesian3());      // vector from camera to a primitive
var toCenterProj = SuperMap3D.Cartesian3.multiplyByScalar(direction, SuperMap3D.Cartesian3.dot(direction, toCenter), new SuperMap3D.Cartesian3()); // project vector onto camera direction vector
var distance = SuperMap3D.Cartesian3.magnitude(toCenterProj);
var pixelSize = camera.frustum.getPixelDimensions(scene.drawingBufferWidth, scene.drawingBufferHeight, distance, scene.pixelRatio, new SuperMap3D.Cartesian2());