WebGLRenderingContext: bufferSubData() method

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

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

Syntax

bufferSubData(target, offset)
bufferSubData(target, offset, srcData)

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.

    When using a {{domxref("WebGL2RenderingContext", "WebGL 2 context", "", 1)}} , 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.

• dstByteOffset

  • : A {{domxref("WebGL_API/Types", "GLintptr")}}  specifying an offset in bytes where the data replacement will start.

• srcData {{optional_inline}} 

  • : An {{jsxref("ArrayBuffer")}} , {{jsxref("SharedArrayBuffer")}} , a {{jsxref("DataView")}} , or a {{jsxref("TypedArray")}}  that will be copied into the data store.

• srcOffset

  • : A {{domxref("WebGL_API/Types", "GLuint")}}  specifying the element index offset where to start reading the buffer.

• length {{optional_inline}} 

  • : A {{domxref("WebGL_API/Types", "GLuint")}}  defaulting to 0.

Return value

None ({{jsxref("undefined")}} ).

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

const canvas = document.getElementById("canvas");
const gl = canvas.getContext("webgl");
const buffer = gl.createBuffer();
const data = new Float32Array([1, 2, 3, 4]);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, 1024, gl.STATIC_DRAW);
gl.bufferSubData(gl.ARRAY_BUFFER, 512, data);

Specifications

{{Specifications}} 

Browser compatibility

{{Compat}} 

See also

• {{domxref("WebGL2RenderingContext.bufferSubData()")}} 
• {{domxref("WebGLRenderingContext.createBuffer()")}} 
• {{domxref("WebGLRenderingContext.bufferData()")}} 
• Other buffers: {{domxref("WebGLFramebuffer")}} , {{domxref("WebGLRenderbuffer")}}