WebGL2RenderingContext: getBufferSubData() method

{{APIRef("WebGL")}} {{AvailableInWorkers}} 

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

Syntax

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

Parameters

• target

  • : A {{domxref("WebGL_API/Types", "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 {{domxref("WebGL_API/Types", "GLintptr")}}  specifying the byte offset from which to start reading from the buffer.

• dstData

  • : A {{jsxref("TypedArray")}}  or a {{jsxref("DataView")}}  object to copy the data to. If dstData is a {{jsxref("DataView")}}  then dstOffset and length are interpreted in bytes, otherwise dstData’s element type is used.

• dstOffset {{optional_inline}} 

  • : A {{domxref("WebGL_API/Types", "GLuint")}}  specifying the element index offset to start writing in dstData.

• length {{optional_inline}} 

  • : A {{domxref("WebGL_API/Types", "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 ({{jsxref("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

{{Specifications}} 

Browser compatibility

{{Compat}} 

See also

• {{domxref("WebGLRenderingContext.bufferData()")}} 
• {{domxref("WebGLRenderingContext.bufferSubData()")}} 
• {{domxref("WebGLRenderingContext.getBufferParameter()")}} 
• {{domxref("WebGL2RenderingContext.copyBufferSubData()")}}