OES_draw_buffers_indexed: blendFuncSeparateiOES() 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 blendFuncSeparateiOES() method of the OES_draw_buffers_indexed WebGL extension defines which function is used when blending pixels for RGB and alpha components separately for a particular draw buffer.

See OES_draw_buffers_indexed.blendFunciOES() for setting RGB and alpha together and WebGLRenderingContext.blendFuncSeparate() for the WebGL 1 version of this method.

Syntax

js
blendFuncSeparateiOES(buf, srcRGB, dstRGB, srcAlpha, dstAlpha)

Parameters

buf

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

srcRGB

A GLenum specifying a multiplier for the red, green and blue (RGB) source blending factors. Accepts the same enums as the srcRGB parameter in WebGLRenderingContext.blendFuncSeparate().

dstRGB

A GLenum specifying a multiplier for the red, green and blue (RGB) destination blending factors. Accepts the same enums as the dstRGB parameter in WebGLRenderingContext.blendFuncSeparate().

srcAlpha

A GLenum specifying a multiplier for the alpha source blending factor. Accepts the same enums as the srcAlpha parameter in WebGLRenderingContext.blendFuncSeparate().

dstAlpha

A GLenum specifying a multiplier for the alpha destination blending factor. Accepts the same enums as the srcAlpha parameter in WebGLRenderingContext.blendFuncSeparate().

Return value

None (undefined).

Exceptions

  • If buf is not a valid value, a gl.INVALID_VALUE error is thrown.
  • If srcRGB, dstRGB, srcAlpha or dstAlpha are not one of the possible values, a gl.INVALID_ENUM error is thrown.
  • The same blending limitations as for WebGLRenderingContext.blendFuncSeparate() 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

The following sets the blend functions for the draw buffers gl.DRAW_BUFFER0 (call where buf is 0) and gl.DRAW_BUFFER1 (call where buf is 1).

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

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

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