ExtentTessellator

Contains class functions to create a mesh or vertex array from a cartographic extent.

See:

Source:

/Source/Core/ExtentTessellator.js

Methods

Creates a mesh from a cartographic extent.

Parameters:

Name	Type	Argument	Default	Description
`description.extent`	Extent			A cartographic extent with north, south, east and west properties in radians.
`description.ellipsoid`	Ellipsoid	<optional>	Ellipsoid.WGS84	The ellipsoid on which the extent lies.
`description.granularity`	Number	<optional>	0.1	The distance, in radians, between each latitude and longitude. Determines the number of positions in the buffer.
`description.surfaceHeight`	Number	<optional>	0.0	The height from the surface of the ellipsoid.
`description.relativetoCenter`	Cartesian3	<optional>	Cartesian3.ZERO	The positions will be computed as `worldPosition.subtract(relativeToCenter)`.
`description.generateTextureCoordinates`	Boolean	<optional>	false	Whether to generate texture coordinates.

Throws:

DeveloperError : description.extent is required and must have north, south, east and west attributes.
DeveloperError : description.extent.north must be in the interval [-Pi/2, Pi/2].
DeveloperError : description.extent.south must be in the interval [-Pi/2, Pi/2].
DeveloperError : description.extent.east must be in the interval [-Pi, Pi].
DeveloperError : description.extent.west must be in the interval [-Pi, Pi].
DeveloperError : description.extent.north must be greater than extent.south.
DeveloperError : description.extent.east must be greater than extent.west.
DeveloperError : description.context is required.

Returns:

Object A mesh containing attributes for positions, possibly texture coordinates and indices from the extent for creating a vertex array. (returns undefined if no indices are found)

Example

// Create a vertex array for rendering a wireframe extent.
var mesh = ExtentTessellator.compute({
    ellipsoid : Ellipsoid.WGS84,
    extent : new Extent(
        CesiumMath.toRadians(-80.0),
        CesiumMath.toRadians(39.0),
        CesiumMath.toRadians(-74.0),
        CesiumMath.toRadians(42.0)
    ),
    granularity : 0.01,
    surfaceHeight : 10000.0
});
mesh = MeshFilters.toWireframeInPlace(mesh);
var va = context.createVertexArrayFromMesh({
    mesh             : mesh,
    attributeIndices : MeshFilters.createAttributeIndices(mesh)
});

See:

<static> computeBuffers

Creates arrays of vertex attributes and indices from a cartographic extent.

Parameters:

Name	Type	Argument	Default	Description
`description.extent`	Extent			A cartographic extent with north, south, east and west properties in radians.
`description.ellipsoid`	Ellipsoid	<optional>	Ellipsoid.WGS84	The ellipsoid on which the extent lies.
`description.granularity`	Number	<optional>	0.1	The distance, in radians, between each latitude and longitude. Determines the number of positions in the buffer.
`description.surfaceHeight`	Number	<optional>	0.0	The height from the surface of the ellipsoid.
`description.relativetoCenter`	Cartesian3	<optional>	Cartesian3.ZERO	The positions will be computed as `worldPosition.subtract(relativeToCenter)`.
`description.generateTextureCoordinates`	Boolean	<optional>	false	Whether to generate texture coordinates.
`description.interleaveTextureCoordinates`	Boolean	<optional>	false	If texture coordinates are generated, whether to interleave the positions and texture coordinates in a single buffer.

Throws:

DeveloperError : description.extent is required and must have north, south, east and west attributes.
DeveloperError : description.extent.north must be in the interval [-Pi/2, Pi/2].
DeveloperError : description.extent.south must be in the interval [-Pi/2, Pi/2].
DeveloperError : description.extent.east must be in the interval [-Pi, Pi].
DeveloperError : description.extent.west must be in the interval [-Pi, Pi].
DeveloperError : description.extent.north must be greater than extent.south. *
DeveloperError : description.extent.east must be greater than extent.west.

Returns:

Object An object with flattened arrays for vertex attributes and indices.

Examples

// Example 1:
// Create a vertex array for a solid extent, with separate positions and texture coordinates.
var buffers = ExtentTessellator.computeBuffers({
    ellipsoid : ellipsoid,
    extent : extent,
    generateTextureCoordinates : true
});

var datatype = ComponentDatatype.FLOAT;
var usage = BufferUsage.STATIC_DRAW;
var positionBuffer = context.createVertexBuffer(datatype.toTypedArray(buffers.positions), usage);
var textureCoordinateBuffer = context.createVertexBuffer(datatype.toTypedArray(buffers.textureCoordinates), usage);
attributes = [{
        index : attributeIndices.position,
        vertexBuffer : positionBuffer,
        componentDatatype : datatype,
        componentsPerAttribute : 3
    }, {
        index : attributeIndices.textureCoordinates,
        vertexBuffer : textureCoordinateBuffer,
        componentDatatype : datatype,
        componentsPerAttribute : 2
    }];
var indexBuffer = context.createIndexBuffer(new Uint16Array(buffers.indices), usage, IndexDatatype.UNSIGNED_SHORT);
var va = context.createVertexArray(attributes, indexBuffer);

// Example 2:
// Create a vertex array for a solid extent, with interleaved positions and texture coordinates.
var buffers = ExtentTessellator.computeBuffers({
    ellipsoid : ellipsoid,
    extent : extent,
    generateTextureCoordinates : true,
    interleaveTextureCoordinates : true
});

var datatype = ComponentDatatype.FLOAT;
var usage = BufferUsage.STATIC_DRAW;
var typedArray = datatype.toTypedArray(buffers.vertices);
var buffer = context.createVertexBuffer(typedArray, usage);
var stride = 5 * datatype.sizeInBytes;
var attributes = [{
        index : attributeIndices.position3D,
        vertexBuffer : buffer,
        componentDatatype : datatype,
        componentsPerAttribute : 3,
        normalize : false,
        offsetInBytes : 0,
        strideInBytes : stride
    }, {
        index : attributeIndices.textureCoordinates,
        vertexBuffer : buffer,
        componentDatatype : datatype,
        componentsPerAttribute : 2,
        normalize : false,
        offsetInBytes : 3 * datatype.sizeInBytes,
        strideInBytes : stride
    }];
var indexBuffer = context.createIndexBuffer(new Uint16Array(buffers.indices), usage, IndexDatatype.UNSIGNED_SHORT);
var vacontext.createVertexArray(attributes, indexBuffer);