Class: PerspectiveFrustum

PerspectiveFrustum

new PerspectiveFrustum()

The cone of sight is defined by six planes. Each plane is represented by a Cartesian object, where the x, y, and z components define the unit vector perpendicular to the plane, and the w component is the distance from the plane to the origin/camera position.

Name Type Default Description
options.fov Number optional

The angle of field of view (FOV), measured in radians.
options.aspectRatio Number optional

The aspect ratio of cone width to height.
options.near Number 1.0 optional

Distance near the plane.
options.far Number 500000000.0 optional

Distance from the far plane.
options.xOffset Number 0.0 optional

The offset in the X direction.
options.yOffset Number 0.0 optional

The offset in the Y direction.
See:
Example
var frustum = new SuperMap3D.PerspectiveFrustum({
    fov : SuperMap3D.Math.PI_OVER_THREE,
    aspectRatio : canvas.clientWidth / canvas.clientHeight
    near : 1.0,
    far : 1000.0
});

Members

aspectRatioNumber

The aspect ratio of the visual cone

Default Value:
undefined

farNumber

Distance from the far plane

Default Value:
500000000.0

fovNumber

The angle of field of view (FOV), measured in radians. If the width is greater than the height, this angle will be used as the horizontal field of view angle; Otherwise, it will be considered as a vertical field of view angle.

Default Value:
undefined

readonly fovyNumber

Obtain the angle of the vertical field of view in radians.

Default Value:
undefined

readonly infiniteProjectionMatrixMatrix4

The perspective projection matrix calculated from the frustum on an infinite plane.

See:

nearNumber

Distance near the plane

Default Value:
1.0

readonly projectionMatrixMatrix4

Obtain the perspective projection matrix calculated from the frustum of the view.

See:

xOffsetNumber

The offset in the X direction.

Default Value:
0.0

yOffsetNumber

The offset in the Y direction.

Default Value:
0.0

Methods

static pack(value, array, startingIndex){Array.<Number>}

Store the provided instance in the provided array.

Name Type Default Description
value PerspectiveFrustum

Instances to be stored
array Array.<Number>

Array for storing instances
startingIndex Number 0 optional

The index position of the starting packaged element in the array.
Returns:
Type Description
Array.<Number> Packaged array

static unpack(array, startingIndex, result){PerspectiveFrustum}

Retrieve an instance from the packaged array.

Name Type Default Description
array Array.<Number>

Packaged array
startingIndex Number 0 optional

The starting index of the element to be unpacked.
result PerspectiveFrustum optional

An instance object used to store results.
Returns:
Type Description
PerspectiveFrustum If the modified result parameters are not provided, return a new perspective projection cone instance.

clone(result){PerspectiveFrustum}

Return a copy of the PerspectiveFrustum instance.

Name Type Description
result PerspectiveFrustum optional

The object that stores the results.
Returns:
Type Description
PerspectiveFrustum The modified result parameters, or a new PerspectiveFrustum instance (if not provided).

computeCullingVolume(position, direction, up){CullingVolume}

Create a cropped body for this viewing cone.

Name Type Description
position Cartesian3

Viewpoint position.
direction Cartesian3

Direction of gaze.
up Cartesian3

Upward direction.
Returns:
Type Description
CullingVolume A cropped object in a given position and direction.
Example
// Check if a bounding volume intersects the frustum.
var cullingVolume = frustum.computeCullingVolume(cameraPosition, cameraDirection, cameraUp);
var intersect = cullingVolume.computeVisibility(boundingVolume);

equals(other){Boolean}

Compare the components of the provided PerspectiveFrustum, return true if they are equal, otherwise return false.

Name Type Description
other PerspectiveFrustum optional

The Perspective Frustum on the right.
Returns:
Type Description
Boolean If they are equal, it is true; otherwise, it is false.

equalsEpsilon(other, relativeEpsilon, absoluteEpsilon){Boolean}

If the provided PerspectiveFrustum components meet the inspection criteria for absolute or relative tolerances, return true; otherwise, return false.

Name Type Default Description
other PerspectiveFrustum

A perspective projection cone for comparison.
relativeEpsilon Number

The relative epsilon tolerance value used for equality testing.
absoluteEpsilon Number relativeEpsilon optional

The absolute epsilon tolerance value used for equality testing.
Returns:
Type Description
Boolean If this object and other objects are within the provided epsilon range, return true; otherwise, return false.

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

Returns the width and height of pixels in meters.

Name Type Description
drawingBufferWidth Number

Draw the width of the buffer.
drawingBufferHeight Number

Draw the height of the buffer.
distance Number

The distance to the near plane, measured in meters.
result Cartesian2

The object that stores the results.
Throws:

  • DrawingBufferWidth must be greater than 0.

    Type
    DeveloperError

  • DrawingBufferHeight must be greater than 0.

    Type
    DeveloperError
Returns:
Type Description
Cartesian2 The modified result parameter or a new instance of Cartesian2 contains the width and height of the pixel in its x and y attributes, respectively.
Examples
// Example 1
// Get the width and height of a pixel.
var pixelSize = camera.frustum.getPixelDimensions(scene.drawingBufferWidth, scene.drawingBufferHeight, 1.0, 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, new SuperMap3D.Cartesian2());