WebGL2RenderingContext: getBufferSubData() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2021.

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

js
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

js
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

BCD tables only load in the browser

See also