WebGLRenderingContext.bufferSubData

The WebGLRenderingContext.bufferSubData() method of the WebGL API updates a subset of a buffer object's data store.

Syntax

// WebGL1: 
void gl.bufferSubData(target, offset, ArrayBuffer srcData); 
void gl.bufferSubData(target, offset, ArrayBufferView srcData); 

// WebGL2: 
void gl.bufferSubData(target, dstByteOffset, ArrayBufferView srcData, srcOffset, 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.
• When using a WebGL 2 context, the following values are available additionally:
  • 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.

offset

A GLintptr specifying an offset in bytes where the data replacement will start.

data Optional

An ArrayBuffer, SharedArrayBuffer or one of the ArrayBufferView typed array types that will be copied into the data store.

srcOffset

A GLuint specifying the element index offset where to start reading the buffer.

length Optional

A GLuint defaulting to 0.

Return value

None.

Exceptions

• A gl.INVALID_VALUE error is thrown if the data would be written past the end of the buffer or if data is null.
• A gl.INVALID_ENUM error is thrown if target is not one of the allowed enums.

Examples

Using bufferSubData

var canvas = document.getElementById('canvas');
var gl = canvas.getContext('webgl');
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, 1024, gl.STATIC_DRAW);
gl.bufferSubData(gl.ARRAY_BUFFER, 512, data);

Specifications

Specification	Status	Comment
WebGL 1.0 The definition of 'bufferSubData' in that specification.	Recommendation	Initial definition for WebGL.
OpenGL ES 2.0 The definition of 'glBufferSubData' in that specification.	Standard	Man page of the OpenGL ES 2 API.
OpenGL ES 3.0 The definition of 'glBufferSubData' in that specification.	Standard	Man page of the (similar) OpenGL ES 3 API. Adds new target buffers: gl.COPY_READ_BUFFER, gl.COPY_WRITE_BUFFER, gl.TRANSFORM_FEEDBACK_BUFFER, gl.UNIFORM_BUFFER, gl.PIXEL_PACK_BUFFER, gl.PIXEL_UNPACK_BUFFER.

Browser compatibility

See also

• WebGLRenderingContext.createBuffer()
• WebGLRenderingContext.bufferData()
• Other buffers: WebGLFramebuffer, WebGLRenderbuffer