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OES_draw_buffers_indexed

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨December 2022⁩.

The OES_draw_buffers_indexed extension is part of the WebGL API and enables the use of different blend options when writing to multiple color buffers simultaneously.

WebGL extensions are available using the WebGLRenderingContext.getExtension() method. For more information, see also Using Extensions in the WebGL tutorial.

Note: This extension is only available to WebGL2 contexts.

Instance methods

OES_draw_buffers_indexed.blendEquationiOES(): Sets both the RGB and alpha blend equations for a particular draw buffer.
OES_draw_buffers_indexed.blendEquationSeparateiOES(): Sets the RGB and alpha blend equations separately for a particular draw buffer.
OES_draw_buffers_indexed.blendFunciOES(): Defines which function is used when blending pixels for a particular draw buffer.
OES_draw_buffers_indexed.blendFuncSeparateiOES(): Defines which function is used when blending pixels for RGB and alpha components separately for a particular draw buffer.
OES_draw_buffers_indexed.colorMaskiOES(): Sets which color components to enable or to disable when drawing or rendering for a particular draw buffer.
OES_draw_buffers_indexed.disableiOES(): Disables blending for a particular draw buffer.
OES_draw_buffers_indexed.enableiOES(): Enables blending for a particular draw buffer.

Examples

Using the `OES_draw_buffers_indexed` extension

Enable the extension with a call to WebGLRenderingContext.getExtension().

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

You can now enable blending, set blending equation, blending function, and color mask for a particular draw buffer.

// For gl.DRAW_BUFFER0
ext.enableiOES(gl.BLEND, 0);
ext.blendEquationiOES(0, gl.FUNC_ADD);
ext.blendFunciOES(0, gl.ONE, gl.ONE);
ext.colorMaskiOES(0, 1, 0, 0, 0);

// For gl.DRAW_BUFFER1
ext.enableiOES(gl.BLEND, 1);
ext.blendEquationSeparateiOES(1, gl.FUNC_ADD, gl.FUNC_SUBTRACT);
ext.blendFuncSeparateiOES(
  1,
  gl.SRC_ALPHA,
  gl.ONE_MINUS_SRC_ALPHA,
  gl.ZERO,
  gl.ZERO,
);
ext.colorMaskiOES(1, 0, 1, 0, 0);

To retrieve settings for a particular draw buffer, use WebGL2RenderingContext.getIndexedParameter().

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

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

You can use WebGLRenderingContext.getParameter() to see how many draw buffers are available.

const maxDrawBuffers = gl.getParameter(gl.MAX_DRAW_BUFFERS);

Specifications

Specification
WebGL OES_draw_buffers_indexed Extension Specification>

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS
`OES_draw_buffers_indexed`	100	100	108	86	16	100	108	69	16	19.0	100	16
`blendEquationSeparateiOES`	100	100	108	86	16	100	108	69	16	19.0	100	16
`blendEquationiOES`	100	100	108	86	16	100	108	69	16	19.0	100	16
`blendFuncSeparateiOES`	100	100	108	86	16	100	108	69	16	19.0	100	16
`blendFunciOES`	100	100	108	86	16	100	108	69	16	19.0	100	16
`colorMaskiOES`	100	100	108	86	16	100	108	69	16	19.0	100	16
`disableiOES`	100	100	108	86	16	100	108	69	16	19.0	100	16
`enableiOES`	100	100	108	86	16	100	108	69	16	19.0	100	16