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WebGL2RenderingContext: getBufferSubData() method

The WebGL2RenderingContext.getBufferSubData() method of the WebGL 2 API reads data from a buffer binding point and writes them to an ArrayBuffer or SharedArrayBuffer.

Syntax

getBufferSubData(target, srcByteOffset, dstData)
getBufferSubData(target, srcByteOffset, dstData, dstOffset)
getBufferSubData(target, srcByteOffset, dstData, dstOffset, length)

Parameters

target

A GLenum specifying the binding point (target). Possible values:

gl.ARRAY_BUFFER: Buffer containing vertex attributes, such as vertex coordinates, texture coordinate data, or vertex color data.
gl.ELEMENT_ARRAY_BUFFER: Buffer used for element indices.
gl.COPY_READ_BUFFER: Buffer for copying from one buffer object to another.
gl.COPY_WRITE_BUFFER: Buffer for copying from one buffer object to another.
gl.TRANSFORM_FEEDBACK_BUFFER: Buffer for transform feedback operations.
gl.UNIFORM_BUFFER: Buffer used for storing uniform blocks.
gl.PIXEL_PACK_BUFFER: Buffer used for pixel transfer operations.
gl.PIXEL_UNPACK_BUFFER: Buffer used for pixel transfer operations.

srcByteOffset

A GLintptr specifying the byte offset from which to start reading from the buffer.

dstData

A TypedArray or a DataView object to copy the data to. If dstData is a DataView then dstOffset and length are interpreted in bytes, otherwise dstData's element type is used.

dstOffset Optional

A GLuint specifying the element index offset to start writing in dstData.

length Optional

A GLuint specifying the number of elements to copy. If this is 0 or not specified, getBufferSubData will copy until the end of dstData.

Return value

None (undefined).

Exceptions

An INVALID_VALUE error is generated if:

offset + returnedData.byteLength would extend beyond the end of the buffer
returnedData is null
offset is less than zero.

An INVALID_OPERATION error is generated if:

zero is bound to target
target is TRANSFORM_FEEDBACK_BUFFER, and any transform feedback object is currently active.

Examples

const buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);

const arrBuffer = new ArrayBuffer(
  vertices.length * Float32Array.BYTES_PER_ELEMENT,
);
gl.getBufferSubData(gl.ARRAY_BUFFER, 0, new Float32Array(arrBuffer));

Specifications

Specification
WebGL 2.0 Specification # 3.7.3

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`SharedArrayBuffer_as_param`	60	79	79	No	47	No	60	60	79	44	No	8.0
`getBufferSubData`	56	79	51	No	43	15	58	58	51	43	15	7.0