Context

Members

<constant> options :Object

Returns the read-only options used to create this context. The webgl property corresponds to the WebGLContextAttributes object used to create the WebGL context. Default values are shown in the code example below.

options.webgl.alpha defaults to false, which can improve performance compared to the standard WebGL default of true. If an application needs to composite Cesium above other HTML elements using alpha-blending, set options.webgl.alpha to true.

options.webgl.failIfMajorPerformanceCaveat defaults to true, which ensures a context is not successfully created if the system has a major performance issue such as only supporting software rendering. The standard WebGL default is false, which is not appropriate for almost any Cesium app.

The other options.webgl properties match the WebGL defaults for WebGLContextAttributes.

options.allowTextureFilterAnisotropic defaults to true, which enables anisotropic texture filtering when the WebGL extension is supported. Check Context#getTextureFilterAnisotropic. Setting this to false will improve performance, but hurt visual quality, especially for horizon views.

Example

{
  webgl : {
    alpha : false,
    depth : true,
    stencil : false,
    antialias : true,
    premultipliedAlpha : true,
    preserveDrawingBuffer : false
    failIfMajorPerformanceCaveat : true
  },
  allowTextureFilterAnisotropic : true
}

Methods

clear

Executes the specified clear command.

Parameters:

Name	Type	Argument	Description
clearCommand	ClearCommand	<optional>	The command with which to clear.
passState	PassState	<optional>	The state for the current rendering pass.

See:

• ClearCommand

createCubeMap

DOC_TBA. options.source can be {ImageData}, {HTMLImageElement}, {HTMLCanvasElement}, or {HTMLVideoElement}.

Throws:

• RuntimeError : When options.pixelDatatype is FLOAT, this WebGL implementation must support the OES_texture_float extension.
• DeveloperError : options.source requires positiveX, negativeX, positiveY, negativeY, positiveZ, and negativeZ faces.
• DeveloperError : Each face in options.sources must have the same width and height.
• DeveloperError : options requires a source field to create an initialized cube map or width and height fields to create a blank cube map.
• DeveloperError : Width must equal height.
• DeveloperError : Width and height must be greater than zero.
• DeveloperError : Width and height must be less than or equal to the maximum cube map size.
• DeveloperError : Invalid options.pixelFormat.
• DeveloperError : options.pixelFormat cannot be DEPTH_COMPONENT or DEPTH_STENCIL.
• DeveloperError : Invalid options.pixelDatatype.

Returns:

CubeMap DOC_TBA.

See:

• Context#createTexture2D
• Context#createTexture2DFromFramebuffer
• Context#createSampler

createFramebuffer

Creates a framebuffer with optional initial color, depth, and stencil attachments. Framebuffers are used for render-to-texture effects; they allow us to render to textures in one pass, and read from it in a later pass.

Parameters:

Name	Type	Argument	Description
options	Object	<optional>	The initial framebuffer attachments as shown in the examplebelow. The possible properties are colorTextures, colorRenderbuffers, depthTexture, depthRenderbuffer, stencilRenderbuffer, depthStencilTexture, and depthStencilRenderbuffer.

Throws:

• DeveloperError : Cannot have both color texture and color renderbuffer attachments.
• DeveloperError : Cannot have both a depth texture and depth renderbuffer attachment.
• DeveloperError : Cannot have both a depth-stencil texture and depth-stencil renderbuffer attachment.
• DeveloperError : Cannot have both a depth and depth-stencil renderbuffer.
• DeveloperError : Cannot have both a stencil and depth-stencil renderbuffer.
• DeveloperError : Cannot have both a depth and stencil renderbuffer.
• DeveloperError : The color-texture pixel-format must be a color format.
• DeveloperError : The depth-texture pixel-format must be DEPTH_COMPONENT.
• DeveloperError : The depth-stencil-texture pixel-format must be DEPTH_STENCIL.
• DeveloperError : The number of color attachments exceeds the number supported.

Returns:

Framebuffer The created framebuffer.

Example

// Create a framebuffer with color and depth texture attachments.
var width = context.getCanvas().clientWidth;
var height = context.getCanvas().clientHeight;
var framebuffer = context.createFramebuffer({
  colorTextures : [context.createTexture2D({
    width : width,
    height : height,
    pixelFormat : PixelFormat.RGBA
  })],
  depthTexture : context.createTexture2D({
    width : width,
    height : height,
    pixelFormat : PixelFormat.DEPTH_COMPONENT,
    pixelDatatype : PixelDatatype.UNSIGNED_SHORT
  })
});

See:

• Context#createTexture2D
• Context#createCubeMap
• Context#createRenderbuffer

createIndexBuffer

Creates an index buffer, which contains typed indices in GPU-controlled memory.

An index buffer can be attached to a vertex array to select vertices for rendering. Context.draw can render using the entire index buffer or a subset of the index buffer defined by an offset and count.

Parameters:

Name	Type	Description
typedArrayOrSizeInBytes	ArrayBufferView | Number	A typed array containing the data to copy to the buffer, or a Number defining the size of the buffer in bytes.
usage	BufferUsage	Specifies the expected usage pattern of the buffer. On some GL implementations, this can significantly affect performance. See BufferUsage.
indexDatatype	IndexDatatype	The datatype of indices in the buffer.

Throws:

• RuntimeError : IndexDatatype.UNSIGNED_INT requires OES_element_index_uint, which is not supported on this system.
• DeveloperError : The size in bytes must be greater than zero.
• DeveloperError : Invalid usage.
• DeveloperError : Invalid indexDatatype.

Returns:

IndexBuffer The index buffer, ready to be attached to a vertex array.

Example

// Example 1. Create a stream index buffer of unsigned shorts that is
// 16 bytes in size.
var buffer = context.createIndexBuffer(16, BufferUsage.STREAM_DRAW,
    IndexDatatype.UNSIGNED_SHORT);

////////////////////////////////////////////////////////////////////////////////

// Example 2. Create a static index buffer containing three unsigned shorts.
var buffer = context.createIndexBuffer(new Uint16Array([0, 1, 2]),
    BufferUsage.STATIC_DRAW, IndexDatatype.UNSIGNED_SHORT)

See:

• Context#createVertexArray
• Context#createVertexBuffer
• Context#draw
• VertexArray
• glGenBuffer
• glBindBuffer with ELEMENT_ARRAY_BUFFER
• glBufferData with ELEMENT_ARRAY_BUFFER

createPickFramebuffer

DOC_TBA

See:

• Scene#pick

createPickId

Creates a unique ID associated with the input object for use with color-buffer picking. The ID has an RGBA color value unique to this context. You must call destroy() on the pick ID when destroying the input object.

Parameters:

Name	Type	Description
object	Object	The object to associate with the pick ID.

Throws:

RuntimeError : Out of unique Pick IDs.

Returns:

Object A PickId object with a color property.

Example

this._pickId = context.createPickId({
  primitive : this,
  id : this.id
});

See:

• Context#getObjectByPickColor

createRenderbuffer

DOC_TBA.

Parameters:

Name	Type	Argument	Description
options	Object	<optional>	DOC_TBA.

Throws:

• DeveloperError : Invalid format.
• DeveloperError : Width must be greater than zero.
• DeveloperError : Width must be less than or equal to the maximum renderbuffer size.
• DeveloperError : Height must be greater than zero.
• DeveloperError : Height must be less than or equal to the maximum renderbuffer size.

Returns:

createRenderbuffer DOC_TBA.

See:

• Context#createFramebuffer

createRenderState

Validates and then finds or creates an immutable render state, which defines the pipeline state for a DrawCommand or ClearCommand. All inputs states are optional. Omitted states use the defaults shown in the example below.

Parameters:

Name	Type	Argument	Default	Description
renderState	Object	<optional>	undefined	The states defining the render state as shown in the example below.

Throws:

• RuntimeError : renderState.lineWidth is out of range.
• DeveloperError : Invalid renderState.frontFace.
• DeveloperError : Invalid renderState.cull.face.
• DeveloperError : scissorTest.rectangle.width and scissorTest.rectangle.height must be greater than or equal to zero.
• DeveloperError : renderState.depthRange.near can't be greater than renderState.depthRange.far.
• DeveloperError : renderState.depthRange.near must be greater than or equal to zero.
• DeveloperError : renderState.depthRange.far must be less than or equal to zero.
• DeveloperError : Invalid renderState.depthTest.func.
• DeveloperError : renderState.blending.color components must be greater than or equal to zero and less than or equal to one
• DeveloperError : Invalid renderState.blending.equationRgb.
• DeveloperError : Invalid renderState.blending.equationAlpha.
• DeveloperError : Invalid renderState.blending.functionSourceRgb.
• DeveloperError : Invalid renderState.blending.functionSourceAlpha.
• DeveloperError : Invalid renderState.blending.functionDestinationRgb.
• DeveloperError : Invalid renderState.blending.functionDestinationAlpha.
• DeveloperError : Invalid renderState.stencilTest.frontFunction.
• DeveloperError : Invalid renderState.stencilTest.backFunction.
• DeveloperError : Invalid renderState.stencilTest.frontOperation.fail.
• DeveloperError : Invalid renderState.stencilTest.frontOperation.zFail.
• DeveloperError : Invalid renderState.stencilTest.frontOperation.zPass.
• DeveloperError : Invalid renderState.stencilTest.backOperation.fail.
• DeveloperError : Invalid renderState.stencilTest.backOperation.zFail.
• DeveloperError : Invalid renderState.stencilTest.backOperation.zPass.
• DeveloperError : renderState.viewport.width must be greater than or equal to zero.
• DeveloperError : renderState.viewport.width must be less than or equal to the maximum viewport width.
• DeveloperError : renderState.viewport.height must be greater than or equal to zero.
• DeveloperError : renderState.viewport.height must be less than or equal to the maximum viewport height.

Example

var defaults = {
    frontFace : WindingOrder.COUNTER_CLOCKWISE,
    cull : {
        enabled : false,
        face : CullFace.BACK
    },
    lineWidth : 1,
    polygonOffset : {
        enabled : false,
        factor : 0,
        units : 0
    },
    scissorTest : {
        enabled : false,
        rectangle : {
            x : 0,
            y : 0,
            width : 0,
            height : 0
        }
    },
    depthRange : {
        near : 0,
        far : 1
    },
    depthTest : {
        enabled : false,
        func : DepthFunction.LESS
     },
    colorMask : {
        red : true,
        green : true,
        blue : true,
        alpha : true
    },
    depthMask : true,
    stencilMask : ~0,
    blending : {
        enabled : false,
        color : {
            red : 0.0,
            green : 0.0,
            blue : 0.0,
            alpha : 0.0
        },
        equationRgb : BlendEquation.ADD,
        equationAlpha : BlendEquation.ADD,
        functionSourceRgb : BlendFunction.ONE,
        functionSourceAlpha : BlendFunction.ONE,
        functionDestinationRgb : BlendFunction.ZERO,
        functionDestinationAlpha : BlendFunction.ZERO
    },
    stencilTest : {
        enabled : false,
        frontFunction : StencilFunction.ALWAYS,
        backFunction : StencilFunction.ALWAYS,
        reference : 0,
        mask : ~0,
        frontOperation : {
            fail : StencilOperation.KEEP,
            zFail : StencilOperation.KEEP,
            zPass : StencilOperation.KEEP
        },
        backOperation : {
            fail : StencilOperation.KEEP,
            zFail : StencilOperation.KEEP,
            zPass : StencilOperation.KEEP
        }
    },
    sampleCoverage : {
        enabled : false,
        value : 1.0,
        invert : false
     },
    dither : true
};

// Same as just context.createRenderState().
var rs = context.createRenderState(defaults);

See:

• DrawCommand
• ClearCommand

createSampler

DOC_TBA

Throws:

• DeveloperError : Invalid sampler.wrapS.
• DeveloperError : Invalid sampler.wrapT.
• DeveloperError : Invalid sampler.minificationFilter.
• DeveloperError : Invalid sampler.magnificationFilter.

See:

• Context#createTexture2D
• Context#createCubeMap

createShaderProgram

Creates a shader program given the GLSL source for a vertex and fragment shader.

The vertex and fragment shader are individually compiled, and then linked together to create a shader program. An exception is thrown if any errors are encountered, as described below.

The program's active uniforms and attributes are queried and can be accessed using the returned shader program. The caller can explicitly define the vertex attribute indices using the optional attributeLocations argument as shown in example two below.

Parameters:

Name	Type	Argument	Default	Description
vertexShaderSource	String			The GLSL source for the vertex shader.
fragmentShaderSource	String			The GLSL source for the fragment shader.
attributeLocations	Object	<optional>	undefined	An optional object that maps vertex attribute names to indices for use with vertex arrays.

Throws:

• RuntimeError : Vertex shader failed to compile.
• RuntimeError : Fragment shader failed to compile.
• RuntimeError : Program failed to link.

Returns:

ShaderProgram The compiled and linked shader program, ready for use in a draw call.

Example

// Example 1. Create a shader program allowing the GL to determine
// attribute indices.
var vs = 'attribute vec4 position; void main() { gl_Position = position; }';
var fs = 'void main() { gl_FragColor = vec4(1.0); }';
var sp = context.createShaderProgram(vs, fs);

////////////////////////////////////////////////////////////////////////////////

// Example 2. Create a shader program with explicit attribute indices.
var vs = 'attribute vec4 position;' +
         'attribute vec3 normal;' +
         'void main() { ... }';
var fs = 'void main() { gl_FragColor = vec4(1.0); }';
var attributes = {
    position : 0,
    normal   : 1
};
sp = context.createShaderProgram(vs, fs, attributes);

See:

• Context#draw
• Context#createVertexArray
• Context#getShaderCache
• glCreateShader
• glShaderSource
• glCompileShader
• glCreateProgram
• glAttachShader
• glLinkProgram
• glGetShaderiv
• glGetActiveUniform
• glGetUniformLocation
• glGetUniform
• glBindAttribLocation
• glGetActiveAttrib
• glGetAttribLocation

createTexture2D

DOC_TBA. options.source can be {ImageData}, {HTMLImageElement}, {HTMLCanvasElement}, or {HTMLVideoElement}.

Throws:

• RuntimeError : When options.pixelFormat is DEPTH_COMPONENT or DEPTH_STENCIL, this WebGL implementation must support WEBGL_depth_texture.
• RuntimeError : When options.pixelDatatype is FLOAT, this WebGL implementation must support the OES_texture_float extension.
• DeveloperError : options requires a source field to create an initialized texture or width and height fields to create a blank texture.
• DeveloperError : Width must be greater than zero.
• DeveloperError : Width must be less than or equal to the maximum texture size.
• DeveloperError : Height must be greater than zero.
• DeveloperError : Height must be less than or equal to the maximum texture size.
• DeveloperError : Invalid options.pixelFormat.
• DeveloperError : Invalid options.pixelDatatype.
• DeveloperError : When options.pixelFormat is DEPTH_COMPONENT, options.pixelDatatype must be UNSIGNED_SHORT or UNSIGNED_INT.
• DeveloperError : When options.pixelFormat is DEPTH_STENCIL, options.pixelDatatype must be UNSIGNED_INT_24_8_WEBGL.
• DeveloperError : When options.pixelFormat is DEPTH_COMPONENT or DEPTH_STENCIL, source cannot be provided.

Returns:

Texture DOC_TBA.

See:

• Context#createTexture2DFromFramebuffer
• Context#createCubeMap
• Context#createSampler

createTexture2DFromFramebuffer

Creates a texture, and copies a subimage of the framebuffer to it. When called without arguments, the texture is the same width and height as the framebuffer and contains its contents.

Parameters:

Name	Type	Argument	Default	Description
pixelFormat	PixelFormat	<optional>	PixelFormat.RGB	The texture's internal pixel format.
framebufferXOffset	PixelFormat	<optional>	0	An offset in the x direction in the framebuffer where copying begins from.
framebufferYOffset	PixelFormat	<optional>	0	An offset in the y direction in the framebuffer where copying begins from.
width	PixelFormat	<optional>	canvas.clientWidth	The width of the texture in texels.
height	PixelFormat	<optional>	canvas.clientHeight	The height of the texture in texels.

Throws:

• DeveloperError : Invalid pixelFormat.
• DeveloperError : pixelFormat cannot be DEPTH_COMPONENT or DEPTH_STENCIL.
• DeveloperError : framebufferXOffset must be greater than or equal to zero.
• DeveloperError : framebufferYOffset must be greater than or equal to zero.
• DeveloperError : framebufferXOffset + width must be less than or equal to getCanvas().clientWidth.
• DeveloperError : framebufferYOffset + height must be less than or equal to getCanvas().clientHeight.

Returns:

Texture A texture with contents from the framebuffer.

Example

// Create a texture with the contents of the framebuffer.
var t = context.createTexture2DFromFramebuffer();

See:

• Context#createTexture2D
• Context#createCubeMap
• Context#createSampler

createTextureAtlas

Creates a new texture atlas with this context.

Parameters:

Name	Type	Argument	Default	Description
options.pixelFormat	PixelFormat	<optional>	PixelFormat.RGBA	The pixel format of the texture.
options.borderWidthInPixels	Number	<optional>	1	The amount of spacing between adjacent images in pixels.
options.initialSize	Cartesian2	<optional>	new Cartesian2(16.0, 16.0)	The initial side lengths of the texture.
options.images	Array	<optional>	undefined	Array of Image to be added to the atlas. Same as calling addImages(images).
options.image	Image	<optional>	undefined	Single image to be added to the atlas. Same as calling addImage(image).

Returns:

TextureAtlas The new texture atlas.

See:

• TextureAtlas

createVertexArray

Creates a vertex array, which defines the attributes making up a vertex, and contains an optional index buffer to select vertices for rendering. Attributes are defined using object literals as shown in Example 1 below.

Parameters:

Name	Type	Argument	Default	Description
attributes	Array	<optional>	undefined	An optional array of attributes.
indexBuffer	IndexBuffer	<optional>	undefined	An optional index buffer.

Throws:

• DeveloperError : Attribute must have a vertexBuffer.
• DeveloperError : Attribute must have a componentsPerAttribute.
• DeveloperError : Attribute must have a valid componentDatatype or not specify it.
• DeveloperError : Attribute must have a strideInBytes less than or equal to 255 or not specify it.
• DeveloperError : Index n is used by more than one attribute.

Returns:

VertexArray The vertex array, ready for use with drawing.

Example

// Example 1. Create a vertex array with vertices made up of three floating point
// values, e.g., a position, from a single vertex buffer.  No index buffer is used.
var positionBuffer = context.createVertexBuffer(12, BufferUsage.STATIC_DRAW);
var attributes = [
    {
        index                  : 0,
        enabled                : true,
        vertexBuffer           : positionBuffer,
        componentsPerAttribute : 3,
        componentDatatype      : ComponentDatatype.FLOAT,
        normalize              : false,
        offsetInBytes          : 0,
        strideInBytes          : 0 // tightly packed
    }
];
var va = context.createVertexArray(attributes);

////////////////////////////////////////////////////////////////////////////////

// Example 2. Create a vertex array with vertices from two different vertex buffers.
// Each vertex has a three-component position and three-component normal.
var positionBuffer = context.createVertexBuffer(12, BufferUsage.STATIC_DRAW);
var normalBuffer = context.createVertexBuffer(12, BufferUsage.STATIC_DRAW);
var attributes = [
    {
        index                  : 0,
        vertexBuffer           : positionBuffer,
        componentsPerAttribute : 3,
        componentDatatype      : ComponentDatatype.FLOAT
    },
    {
        index                  : 1,
        vertexBuffer           : normalBuffer,
        componentsPerAttribute : 3,
        componentDatatype      : ComponentDatatype.FLOAT
    }
];
var va = context.createVertexArray(attributes);

////////////////////////////////////////////////////////////////////////////////

// Example 3. Creates the same vertex layout as Example 2 using a single
// vertex buffer, instead of two.
var buffer = context.createVertexBuffer(24, BufferUsage.STATIC_DRAW);
var attributes = [
    {
        vertexBuffer           : buffer,
        componentsPerAttribute : 3,
        componentDatatype      : ComponentDatatype.FLOAT,
        offsetInBytes          : 0,
        strideInBytes          : 24
    },
    {
        vertexBuffer           : buffer,
        componentsPerAttribute : 3,
        componentDatatype      : ComponentDatatype.FLOAT,
        normalize              : true,
        offsetInBytes          : 12,
        strideInBytes          : 24
    }
];
var va = context.createVertexArray(attributes);

See:

• Context#createVertexArrayFromGeometry
• Context#createVertexBuffer
• Context#createIndexBuffer
• Context#draw

createVertexArrayFromGeometry

Creates a vertex array from a geometry. A geometry contains vertex attributes and optional index data in system memory, whereas a vertex array contains vertex buffers and an optional index buffer in WebGL memory for use with rendering.

The geometry argument should use the standard layout like the geometry returned by BoxGeometry.

creationArguments can have four properties:

• geometry: The source geometry containing data used to create the vertex array.
• attributeLocations: An object that maps geometry attribute names to vertex shader attribute locations.
• bufferUsage: The expected usage pattern of the vertex array's buffers. On some WebGL implementations, this can significantly affect performance. See BufferUsage. Default: BufferUsage.DYNAMIC_DRAW.
• vertexLayout: Determines if all attributes are interleaved in a single vertex buffer or if each attribute is stored in a separate vertex buffer. Default: VertexLayout.SEPARATE.

If creationArguments is not specified or the geometry contains no data, the returned vertex array is empty.

Parameters:

Name	Type	Argument	Default	Description
creationArguments	Object	<optional>	undefined	An object defining the geometry, attribute indices, buffer usage, and vertex layout used to create the vertex array.

Throws:

• RuntimeError : Each attribute list must have the same number of vertices.
• DeveloperError : The geometry must have zero or one index lists.
• DeveloperError : Index n is used by more than one attribute.

Example

// Example 1. Creates a vertex array for rendering a box.  The default dynamic draw
// usage is used for the created vertex and index buffer.  The attributes are not
// interleaved by default.
var geometry = new BoxGeometry();
var va = context.createVertexArrayFromGeometry({
    geometry           : geometry,
    attributeLocations : GeometryPipeline.createAttributeLocations(geometry),
});

////////////////////////////////////////////////////////////////////////////////

// Example 2. Creates a vertex array with interleaved attributes in a
// single vertex buffer.  The vertex and index buffer have static draw usage.
var va = context.createVertexArrayFromGeometry({
    geometry           : geometry,
    attributeLocations : GeometryPipeline.createAttributeLocations(geometry),
    bufferUsage        : BufferUsage.STATIC_DRAW,
    vertexLayout       : VertexLayout.INTERLEAVED
});

////////////////////////////////////////////////////////////////////////////////

// Example 3.  When the caller destroys the vertex array, it also destroys the
// attached vertex buffer(s) and index buffer.
va = va.destroy();

See:

• Context#createVertexArray
• Context#createVertexBuffer
• Context#createIndexBuffer
• GeometryPipeline.createAttributeLocations
• ShaderProgram

createVertexBuffer

Creates a vertex buffer, which contains untyped vertex data in GPU-controlled memory.

A vertex array defines the actual makeup of a vertex, e.g., positions, normals, texture coordinates, etc., by interpreting the raw data in one or more vertex buffers.

Parameters:

Name	Type	Description
typedArrayOrSizeInBytes	ArrayBufferView | Number	A typed array containing the data to copy to the buffer, or a Number defining the size of the buffer in bytes.
usage	BufferUsage	Specifies the expected usage pattern of the buffer. On some GL implementations, this can significantly affect performance. See BufferUsage.

Throws:

• DeveloperError : The size in bytes must be greater than zero.
• DeveloperError : Invalid usage.

Returns:

VertexBuffer The vertex buffer, ready to be attached to a vertex array.

Example

// Example 1. Create a dynamic vertex buffer 16 bytes in size.
var buffer = context.createVertexBuffer(16, BufferUsage.DYNAMIC_DRAW);

////////////////////////////////////////////////////////////////////////////////

// Example 2. Create a dynamic vertex buffer from three floating-point values.
// The data copied to the vertex buffer is considered raw bytes until it is
// interpreted as vertices using a vertex array.
var positionBuffer = context.createVertexBuffer(new Float32Array([0, 0, 0]),
    BufferUsage.STATIC_DRAW);

See:

• Context#createVertexArray
• Context#createIndexBuffer
• glGenBuffer
• glBindBuffer with ARRAY_BUFFER
• glBufferData with ARRAY_BUFFER

draw

Executes the specified draw command.

Parameters:

Name	Type	Argument	Description
drawCommand	DrawCommand		The command with which to draw.
passState	PassState	<optional>	The state for the current rendering pass

Throws:

• DeveloperError : drawCommand.offset must be omitted or greater than or equal to zero.
• DeveloperError : drawCommand.count must be omitted or greater than or equal to zero.
• DeveloperError : Program validation failed.
• DeveloperError : Framebuffer is not complete.

Example

// Example 1.  Draw a single triangle specifying only required arguments
context.draw({
    primitiveType : PrimitiveType.TRIANGLES,
    shaderProgram : sp,
    vertexArray   : va,
});

////////////////////////////////////////////////////////////////////////////////

// Example 2.  Draw a single triangle specifying every argument
context.draw({
    primitiveType : PrimitiveType.TRIANGLES,
    offset        : 0,
    count         : 3,
    framebuffer   : fb,
    shaderProgram : sp,
    vertexArray   : va,
    renderState   : rs
});

See:

• Context#createShaderProgram
• Context#createVertexArray
• Context#createFramebuffer
• Context#createRenderState

getAlphaBits

Returns the number of alpha bits per component in the default framebuffer's color buffer. The minimum is eight.

The alpha channel is used for GL destination alpha operations and by the HTML compositor to combine the color buffer with the rest of the page.

Returns:

Number The number of alpha bits per component in the color buffer.

See:

• glGet with ALPHA_BITS.

getAntialias

Returns true if the WebGL context supports antialiasing. By default antialiasing is requested, but it is not supported by all systems.

Returns:

Boolean true if antialiasing is supported.

getBlueBits

Returns the number of blue bits per component in the default framebuffer's color buffer. The minimum is eight.

Returns:

Number The number of blue bits per component in the color buffer.

See:

• glGet with BLUE_BITS.

getCanvas

Returns the canvas assoicated with this context.

Returns:

HTMLCanvasElement The canvas assoicated with this context.

getDefaultCubeMap

Returns a cube map, where each face is a 1x1 RGBA texture initialized to [255, 255, 255, 255]. This can be used as a placeholder cube map while other cube maps are downloaded.

Returns:

getDefaultTexture

Returns a 1x1 RGBA texture initialized to [255, 255, 255, 255]. This can be used as a placeholder texture while other textures are downloaded.

Returns:

getDepthBits

Returns the number of depth bits per pixel in the default bound framebuffer. The minimum is 16 bits; most implementations will have 24 bits.

Returns:

Number The number of depth bits per pixel in the default bound framebuffer.

See:

• glGet with DEPTH_BITS.

getDepthTexture

Returns true if WEBGL_depth_texture is supported. This extension provides access to depth textures that, for example, can be attached to framebuffers for shadow mapping.

Returns:

Boolean true if WEBGL_depth_texture is supported; otherwise, false.

See:

• WEBGL_depth_texture

getDrawBuffers

Returns true if the WEBGL_draw_buffers extension is supported. This extensions provides support for multiple render targets. The framebuffer object can have mutiple color attachments and the GLSL fragment shader can write to the built-in output array gl_FragData. A shader using this feature needs to explicitly enable the extension with #extension GL_EXT_draw_buffers : enable.

Returns:

Boolean true if WEBGL_draw_buffers is supported; otherwise, false.

See:

• WEBGL_draw_buffers

getDrawingBufferHeight

Returns the drawingBufferWidth of the underlying GL context.

Returns:

Number The value in the drawingBufferWidth property of the underlying GL context.

See:

• drawingBufferWidth

getDrawingBufferWidth

Returns the drawingBufferHeight of the underlying GL context.

Returns:

Number The value in the drawingBufferHeight property of the underlying GL context.

See:

• drawingBufferHeight

getElementIndexUint

Returns true if the OES_element_index_uint extension is supported. This extension allows the use of unsigned int indices, which can improve performance by eliminating batch breaking caused by unsigned short indices.

Returns:

Boolean true if OES_element_index_uint is supported; otherwise, false.

See:

• OES_element_index_uint

getFloatingPointTexture

Returns true if OES_texture_float is supported. This extension provides access to floating point textures that, for example, can be attached to framebuffers for high dynamic range.

Returns:

Boolean true if OES_texture_float is supported; otherwise, false.

See:

• OES_texture_float

getFragmentDepth

Returns true if the EXT_frag_depth extension is supported. This extension provides access to the gl_FragDepthEXT built-in output variable from GLSL fragment shaders. A shader using these functions still needs to explicitly enable the extension with #extension GL_EXT_frag_depth : enable.

Returns:

Boolean true if EXT_frag_depth is supported; otherwise, false.

See:

• EXT_frag_depth

getGreenBits

Returns the number of green bits per component in the default framebuffer's color buffer. The minimum is eight.

Returns:

Number The number of green bits per component in the color buffer.

See:

• glGet with GREEN_BITS.

getId

Returns a unique ID for this context.

Returns:

String A unique ID for this context.

getLogShaderCompilation

DOC_TBA

See:

• Context#setLogShaderCompilation

getMaximumAliasedLineWidth

Returns the maximum aliased line width, in pixels, supported by this WebGL implementation. It will be at least one.

Returns:

Number The maximum aliased line in pixels.

See:

• Context#getMinimumAliasedLineWidth
• glGet with ALIASED_LINE_WIDTH_RANGE.

getMaximumAliasedPointSize

Returns the maximum aliased point size, in pixels, supported by this WebGL implementation. It will be at least one.

Returns:

Number The maximum aliased point size in pixels.

See:

• Context#getMinimumAliasedPointSize
• glGet with ALIASED_POINT_SIZE_RANGE.

getMaximumColorAttachments

Returns the maximum number of color attachments supported.

Returns:

Number The maximum number of color attachments supported.

getMaximumCombinedTextureImageUnits

Returns the maximum number of texture units that can be used from the vertex and fragment shader with this WebGL implementation. The minimum is eight. If both shaders access the same texture unit, this counts as two texture units.

Returns:

Number The maximum supported texture image units.

See:

• Context#getMaximumTextureImageUnits
• Context#getMaximumVertexTextureImageUnits
• glGet with MAX_COMBINED_TEXTURE_IMAGE_UNITS.

getMaximumCubeMapSize

Returns the approximate maximum cube mape width and height supported by this WebGL implementation. The minimum is 16, but most desktop and laptop implementations will support much larger sizes like 8,192.

Returns:

Number The approximate maximum cube mape width and height.

See:

• Context#createCubeMap
• Context#getMaximumTextureSize
• glGet with MAX_CUBE_MAP_TEXTURE_SIZE.

getMaximumDrawBuffers

Returns the maximum number of simultaneous outputs that may be written in a fragment shader.

Returns:

Number The maximum number of draw buffers supported.

getMaximumFragmentUniformVectors

Returns the maximum number of vec4, ivec4, and bvec4 uniforms that can be used by a fragment shader with this WebGL implementation. The minimum is 16.

Returns:

Number The maximum number of vec4, ivec4, and bvec4 uniforms that can be used by a fragment shader.

See:

• Context#getMaximumVertexUniformVectors
• glGet with MAX_FRAGMENT_UNIFORM_VECTORS.

getMaximumRenderbufferSize

Returns the maximum renderbuffer width and height supported by this WebGL implementation. The minimum is 16, but most desktop and laptop implementations will support much larger sizes like 8,192.

Returns:

Number The maximum renderbuffer width and height.

See:

• Context#createRenderbuffer
• glGet with MAX_RENDERBUFFER_SIZE.

getMaximumTextureFilterAnisotropy

DOC_TBA

See:

• Context#getTextureFilterAnisotropic

getMaximumTextureImageUnits

Returns the maximum number of texture units that can be used from the fragment shader with this WebGL implementation. The minimum is eight.

Returns:

Number The maximum number of texture units that can be used from the fragment shader.

See:

• Context#getMaximumCombinedTextureImageUnits
• Context#getMaximumVertexTextureImageUnits
• glGet with MAX_TEXTURE_IMAGE_UNITS.

getMaximumTextureSize

Returns the approximate maximum texture width and height supported by this WebGL implementation. The minimum is 64, but most desktop and laptop implementations will support much larger sizes like 8,192.

Returns:

Number The approximate maximum texture width and height.

See:

• Context#createTexture2D
• Context#getMaximumCubeMapSize
• glGet with MAX_TEXTURE_SIZE.

getMaximumVaryingVectors

Returns the maximum number of vec4 varying variables supported by this WebGL implementation. The minimum is eight. Matrices and arrays count as multiple vec4s.

Returns:

Number Returns the maximum number of vec4 varying variables.

See:

• glGet with MAX_VARYING_VECTORS.

getMaximumVertexAttributes

Returns the maximum number of vec4 vertex attributes supported by this WebGL implementation. The minimum is eight.

Returns:

Number The maximum number of vec4 vertex attributes.

See:

• Context#createVertexArray
• glGet with MAX_VERTEX_ATTRIBS.

getMaximumVertexTextureImageUnits

Returns the maximum number of texture units that can be used from the vertex shader with this WebGL implementation. The minimum is zero, which means the GL does not support vertex texture fetch.

Returns:

Number The maximum number of texture units that can be used from the vertex shader.

See:

• Context#getMaximumCombinedTextureImageUnits
• Context#getMaximumTextureImageUnits
• glGet with MAX_VERTEX_TEXTURE_IMAGE_UNITS.

getMaximumVertexUniformVectors

Returns the maximum number of vec4, ivec4, and bvec4 uniforms that can be used by a vertex shader with this WebGL implementation. The minimum is 16.

Returns:

Number The maximum number of vec4, ivec4, and bvec4 uniforms that can be used by a vertex shader.

See:

• Context#getMaximumFragmentUniformVectors
• glGet with MAX_VERTEX_UNIFORM_VECTORS.

getMaximumViewportHeight

Returns the maximum supported height of the viewport. It will be at least as large as the visible height of the associated canvas.

Returns:

Number The maximum supported height of the viewport.

See:

• Context#getMaximumViewportHeight
• glGet with MAX_VIEWPORT_DIMS.

getMaximumViewportWidth

Returns the maximum supported width of the viewport. It will be at least as large as the visible width of the associated canvas.

Returns:

Number The maximum supported width of the viewport.

See:

• Context#getMaximumViewportHeight
• glGet with MAX_VIEWPORT_DIMS.

getMinimumAliasedLineWidth

Returns the minimum aliased line width, in pixels, supported by this WebGL implementation. It will be at most one.

Returns:

Number The minimum aliased line in pixels.

See:

• Context#getMaximumAliasedLineWidth
• glGet with ALIASED_LINE_WIDTH_RANGE.

getMinimumAliasedPointSize

Returns the minimum aliased point size, in pixels, supported by this WebGL implementation. It will be at most one.

Returns:

Number The minimum aliased point size in pixels.

See:

• Context#getMaximumAliasedPointSize
• glGet with ALIASED_POINT_SIZE_RANGE.

getObjectByPickColor

Gets the object associated with a pick color.

Parameters:

Name	Type	Description
The	Color	pick color.

Returns:

Object The object associated with the pick color, or undefined if no object is associated with that color.

Example

var object = context.getObjectByPickColor(pickColor);

See:

• Context#createPickId

getRedBits

Returns the number of red bits per component in the default framebuffer's color buffer. The minimum is eight.

Returns:

Number The number of red bits per component in the color buffer.

See:

• glGet with RED_BITS.

getRenderer

Returns the name of the renderer/configuration/hardware platform. For example, this may be the model of the video card, e.g., 'GeForce 8800 GTS/PCI/SSE2', or the browser-dependent name of the GL implementation, e.g. 'Mozilla' or 'ANGLE.'

Returns:

String The name of the renderer.

See:

• glGetString with RENDERER.
• ANGLE

getShaderCache

DOC_TBA

See:

• Context#createShaderProgram

getShadingLanguageVersion

Returns the version or release number for the shading language of the form WebGL<space>GLSL<space>ES<space><version number><space><vendor-specific information>.

Returns:

String The version or release number for the shading language.

See:

• glGetString with SHADING_LANGUAGE_VERSION.

getStandardDerivatives

Returns true if the OES_standard_derivatives extension is supported. This extension provides access to dFdx, dFdy, and fwidth functions from GLSL. A shader using these functions still needs to explicitly enable the extension with #extension GL_OES_standard_derivatives : enable.

Returns:

Boolean true if OES_standard_derivatives is supported; otherwise, false.

See:

• OES_standard_derivatives

getStencilBits

Returns the number of stencil bits per pixel in the default bound framebuffer. The minimum is eight bits.

Returns:

Number The number of stencil bits per pixel in the default bound framebuffer.

See:

• glGet with STENCIL_BITS.

getTextureFilterAnisotropic

DOC_TBA

Returns:

Boolean true if EXT_texture_filter_anisotropic is supported; otherwise, false.

See:

• EXT_texture_filter_anisotropic

getThrowOnWebGLError

DOC_TBA

See:

• Context#setThrowOnWebGLError

getUniformState

DOC_TBA

getValidateFramebuffer

DOC_TBA

See:

• Context#setValidateFramebuffer

getValidateShaderProgram

DOC_TBA

See:

• Context#setValidateShaderProgram

getVendor

Returns the company responsible for the WebGL implementation.

Returns:

String The company responsible for the WebGL implementation.

See:

• glGetString with VENDOR.

getVersion

Returns the WebGL version or release number of the form <WebGL><space><version number><space><vendor-specific information>.

Returns:

String The WebGL version or release number.

See:

• glGetString with VERSION.

getVertexArrayObject

Returns true if the OES_vertex_array_object extension is supported. This extension can improve performance by reducing the overhead of switching vertex arrays. When enabled, this extension is automatically used by VertexArray.

Returns:

Boolean true if OES_vertex_array_object is supported; otherwise, false.

See:

• OES_vertex_array_object

readPixels

DOC_TBA

Throws:

• DeveloperError : readState.width must be greater than zero.
• DeveloperError : readState.height must be greater than zero.

setLogShaderCompilation

DOC_TBA

See:

• Context#getLogShaderCompilation

setThrowOnWebGLError

DOC_TBA

Performance:

DOC_TBA: slow.

See:

• Context#setValidateFramebuffer
• Context#setValidateShaderProgram
• Context#getThrowOnWebGLError

setValidateFramebuffer

DOC_TBA

Performance:

DOC_TBA: slow.

See:

• Context#setValidateShaderProgram
• Context#getValidateFramebuffer

setValidateShaderProgram

DOC_TBA

Performance:

DOC_TBA: slow.

See:

• Context#setValidateFramebuffer
• Context#getValidateShaderProgram