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.
| 参数名称 | 类型 | 描述信息 | ||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
options |
object |
可选
An object with the following properties:
|
使用示例:
const frustum = new Cesium.PerspectiveOffCenterFrustum({
left : -1.0,
right : 1.0,
top : 1.0,
bottom : -1.0,
near : 1.0,
far : 100.0
});参考:
成员(属性)
Defines the bottom clipping plane.
-
默认值:
undefined
The distance of the far plane.
-
默认值:
500000000.0
readonly infiniteProjectionMatrix : Matrix4
Gets the perspective projection matrix computed from the view frustum with an infinite far plane.
Defines the left clipping plane.
-
默认值:
undefined
The distance of the near plane.
-
默认值:
1.0
readonly projectionMatrix : Matrix4
Gets the perspective projection matrix computed from the view frustum.
The projection matrix will be recomputed if any frustum parameters have changed.
Defines the right clipping plane.
-
默认值:
undefined
Defines the top clipping plane.
-
默认值:
undefined
方法
Returns a duplicate of a PerspectiveOffCenterFrustum instance.
| 参数名称 | 类型 | 描述信息 |
|---|---|---|
result |
PerspectiveOffCenterFrustum | 可选 The object onto which to store the result. |
返回值:
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.
| 参数名称 | 类型 | 描述信息 |
|---|---|---|
position |
Cartesian3 | The eye position. |
direction |
Cartesian3 | The view direction. |
up |
Cartesian3 | The up direction. |
返回值:
A culling volume at the given position and orientation.
使用示例:
// Check if a bounding volume intersects the frustum.
const cullingVolume = frustum.computeCullingVolume(cameraPosition, cameraDirection, cameraUp);
const intersect = cullingVolume.computeVisibility(boundingVolume);
Compares the provided PerspectiveOffCenterFrustum componentwise and returns
true if they are equal, false otherwise.
| 参数名称 | 类型 | 描述信息 |
|---|---|---|
other |
PerspectiveOffCenterFrustum | 可选 The right hand side PerspectiveOffCenterFrustum. |
返回值:
true if they are equal, false otherwise.
Compares the provided PerspectiveOffCenterFrustum componentwise and returns
true if they pass an absolute or relative tolerance test,
false otherwise.
| 参数名称 | 类型 | 默认值 | 描述信息 |
|---|---|---|---|
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. |
返回值:
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.
| 参数名称 | 类型 | 描述信息 |
|---|---|---|
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. |
返回值:
The modified result parameter or a new instance of
Cartesian2 with the pixel's width and height in the x and y properties, respectively.
Throws:
-
DeveloperError : drawingBufferWidth must be greater than zero.
-
DeveloperError : drawingBufferHeight must be greater than zero.
-
DeveloperError : pixelRatio must be greater than zero.
使用示例s:
// Example 1
// Get the width and height of a pixel.
const pixelSize = camera.frustum.getPixelDimensions(scene.drawingBufferWidth, scene.drawingBufferHeight, 1.0, scene.pixelRatio, new Cesium.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.
const position = camera.position;
const direction = camera.direction;
const toCenter = Cesium.Cartesian3.subtract(primitive.boundingVolume.center, position, new Cesium.Cartesian3()); // vector from camera to a primitive
const toCenterProj = Cesium.Cartesian3.multiplyByScalar(direction, Cesium.Cartesian3.dot(direction, toCenter), new Cesium.Cartesian3()); // project vector onto camera direction vector
const distance = Cesium.Cartesian3.magnitude(toCenterProj);
const pixelSize = camera.frustum.getPixelDimensions(scene.drawingBufferWidth, scene.drawingBufferHeight, distance, scene.pixelRatio, new Cesium.Cartesian2());