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OES_draw_buffers_indexed: blendEquationSeparateiOES() method

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

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

Syntax

js

blendEquationSeparateiOES(buf, modeRGB, modeAlpha)

Parameters

buf

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

modeRGB

A GLenum specifying how source and destination RGB color components are combined. Accepts the same enums as the modeRGB parameter in WebGLRenderingContext.blendEquationSeparate().

modeAlpha

A GLenum specifying how source and destination alpha color components are combined. Accepts the same enums as the modeAlpha parameter in WebGLRenderingContext.blendEquationSeparate().

Return value

None (undefined).

Exceptions

  • If buf is not a valid value, a gl.INVALID_VALUE error is thrown.
  • If modeRGB or modeAlpha are not set to one of the possible values, a gl.INVALID_ENUM error is thrown.

Examples

Setting and getting blend equations

The following sets the blend equations 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.blendEquationSeparateiOES(0, gl.FUNC_ADD, gl.FUNC_SUBTRACT);
ext.blendEquationSeparateiOES(1, gl.FUNC_ADD, gl.FUNC_SUBTRACT);

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

js

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

// for gl.DRAW_BUFFER1
gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 1);
gl.getIndexedParameter(gl.BLEND_EQUATION_ALPHA, 1);

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
blendEquationSeparateiOES 100 100 108 No 86 16 100 100 108 69 16 19.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/OES_draw_buffers_indexed/blendEquationSeparateiOES