OES_draw_buffers_indexed: blendEquationiOES() method

Baseline 2022

Newly available

Since December 2022, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The blendEquationiOES() method of the OES_draw_buffers_indexed WebGL extension sets both the RGB blend and alpha blend equations for a particular draw buffer.

See OES_draw_buffers_indexed.blendEquationSeparateiOES() for setting RGB and alpha separately and WebGLRenderingContext.blendEquation() for the WebGL 1 version of this method.


blendEquationiOES(buf, mode)



An integer i specifying the draw buffer associated with the constant gl.DRAW_BUFFERi, see WebGL draw buffer constants.


A GLenum specifying how source and destination colors are combined. Accepts the same enums as the mode parameter in WebGLRenderingContext.blendEquation().

Return value

None (undefined).


  • If buf is not a valid value, a gl.INVALID_VALUE error is thrown.
  • If mode is not one of the possible values, a gl.INVALID_ENUM error is thrown.


Setting and getting blend equations

You can set the blend equations for the gl.DRAW_BUFFER0 and gl.DRAW_BUFFER1 draw buffers like this:

const ext = gl.getExtension("OES_draw_buffers_indexed");

ext.blendEquationiOES(0, gl.FUNC_ADD);
ext.blendEquationiOES(1, gl.FUNC_SUBTRACT);

To get the blend equations for the gl.DRAW_BUFFER0 and gl.DRAW_BUFFER1 draw buffers, query the BLEND_EQUATION_RGB and BLEND_EQUATION_ALPHA constants using WebGL2RenderingContext.getIndexedParameter():

// For gl.DRAW_BUFFER0
gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 0);
gl.getIndexedParameter(gl.BLEND_EQUATION_ALPHA, 0);

// For gl.DRAW_BUFFER0
gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 1);
gl.getIndexedParameter(gl.BLEND_EQUATION_ALPHA, 1);


WebGL OES_draw_buffers_indexed Extension Specification

Browser compatibility

BCD tables only load in the browser

See also