OES_draw_buffers_indexed: blendFunciOES() 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 blendFunciOES() method of the OES_draw_buffers_indexed WebGL extension defines which function is used when blending pixels for a particular draw buffer.

See OES_draw_buffers_indexed.blendFuncSeparateiOES() for setting RGB and alpha components separately and WebGLRenderingContext.blendFunc() for the WebGL 1 version of this method.

Syntax

js
blendFunciOES(buf, src, dst)

Parameters

buf

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

src

A GLenum specifying a multiplier for the source blending factors. Accepts the same enums as the sfactor parameter in WebGLRenderingContext.blendFunc().

dst

A GLenum specifying a multiplier for the destination blending factors. Accepts the same enums as the dfactor parameter in WebGLRenderingContext.blendFunc().

Return value

None (undefined).

Exceptions

  • If buf is not a valid value, a gl.INVALID_VALUE error is thrown.
  • If src or dst are not one of the possible values, a gl.INVALID_ENUM error is thrown.
  • The same blending limitations as for WebGLRenderingContext.blendFunc() apply: If a constant color and a constant alpha value are used together as source and destination factors, a gl.INVALID_ENUM error is thrown.

Examples

Setting and getting blend functions

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

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

ext.blendFunciOES(0, gl.ONE, gl.ONE);
ext.blendFunciOES(1, gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);

To get the blend functions for the gl.DRAW_BUFFER0 and gl.DRAW_BUFFER1 draw buffers, query the BLEND_SRC_RGB, BLEND_SRC_ALPHA, BLEND_DST_RGB, and BLEND_DST_ALPHA constants using WebGL2RenderingContext.getIndexedParameter():

js
// For gl.DRAW_BUFFER0
gl.getIndexedParameter(gl.BLEND_SRC_RGB, 0);
gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 0);
gl.getIndexedParameter(gl.BLEND_DST_RGB, 0);
gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 0);

// For gl.DRAW_BUFFER0
gl.getIndexedParameter(gl.BLEND_SRC_RGB, 1);
gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 1);
gl.getIndexedParameter(gl.BLEND_DST_RGB, 1);
gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 1);

Specifications

Specification
WebGL OES_draw_buffers_indexed Extension Specification

Browser compatibility

BCD tables only load in the browser

See also