Web/API/WebGLRenderingContext/blendFuncSeparate

The WebGLRenderingContext.blendFuncSeparate() method of the WebGL API defines which function is used for blending pixel arithmetic for RGB and alpha components separately.

Syntax

void gl.blendFuncSeparate(srcRGB, dstRGB, srcAlpha, dstAlpha);

Parameters

srcRGB: A GLenum specifying a multiplier for the red, green and blue (RGB) source blending factors. The default value is gl.ONE. For possible values, see below.
dstRGB: A GLenum specifying a multiplier for the red, green and blue (RGB) destination blending factors. The default value is gl.ZERO. For possible values, see below.
srcAlpha: A GLenum specifying a multiplier for the alpha source blending factor. The default value is gl.ONE. For possible values, see below.
dstAlpha: A GLenum specifying a multiplier for the alpha destination blending factor. The default value is gl.ZERO. For possible values, see below.

Return value

None.

Exceptions

If srcRGB, dstRGB, srcAlpha, or dstAlpha is not one of the listed possible values, a gl.INVALID_ENUM error is thrown.
If a constant color and a constant alpha value are used together as source (srcRGB) and destination (dstRGB) factors, a gl.INVALID_ENUM error is thrown.

Constants

The following constants can be used for srcRGB, dstRGB, srcAlpha, and dstAlpha

The formulas for the blending factors can be described like this (all RGBA values are between 0 and 1):

color(RGB) = (sourceColor * srcRGB) + (destinationColor * dstRGB)
color(A) = (sourceAlpha * srcAlpha) + (destinationAlpha * dstAlpha)

Constant	RGB factor	Alpha factor	Description
`gl.ZERO`	0,0,0	0	Multiplies all colors by 0.
`gl.ONE`	1,1,1,1	1	Multiplies all colors by 1.
`gl.SRC_COLOR`	R_S, G_S, B_S	A_S	Multiplies all colors by the source colors.
`gl.ONE_MINUS_SRC_COLOR`	1-R_S, 1-G_S, 1-B_S	1-A_S	Multiplies all colors by 1 minus each source color.
`gl.DST_COLOR`	R_D, G_D, B_D	A_D	Multiplies all colors by the destination color.
`gl.ONE_MINUS_DST_COLOR`	1-R_D, 1-G_D, 1-B_D	1-A_D	Multiplies all colors by 1 minus each destination color.
`gl.SRC_ALPHA`	A_S, A_S, A_S	A_S	Multiplies all colors by the source alpha color.
`gl.ONE_MINUS_SRC_ALPHA`	1-A_S, 1-A_S, 1-A_S	1-A_S	Multiplies all colors by 1 minus the source alpha color.
`gl.DST_ALPHA`	A_D, A_D, A_D	A_D	Multiplies all colors by the destination alpha color.
`gl.ONE_MINUS_DST_ALPHA`	1-A_D, 1-A_D, 1-A_D	1-A_D	Multiplies all colors by 1 minus the destination alpha color.
`gl.CONSTANT_COLOR`	R_C, G_C, B_C	A_C	Multiplies all colors by a constant color.
`gl.ONE_MINUS_CONSTANT_COLOR`	1-R_C, 1-G_C, 1-B_C	1-A_C	Multiplies all colors by 1 minus a constant color.
`gl.CONSTANT_ALPHA`	A_C, A_C, A_C	A_C	Multiplies all colors by a constant alpha value.
`gl.ONE_MINUS_CONSTANT_ALPHA`	1-A_C, 1-A_C, 1-A_C	1-A_C	Multiplies all colors by 1 minus a constant alpha value.
`gl.SRC_ALPHA_SATURATE`	min(A_S, 1 - A_D), min(A_S, 1 - A_D), min(A_S, 1 - A_D)	1	Multiplies the RGB colors by the smaller of either the source alpha color or the value of 1 minus the destination alpha color. The alpha value is multiplied by 1.

Examples

To use the blend function, you first have to activate blending with WebGLRenderingContext.enable() with the argument gl.BLEND.

gl.enable(gl.BLEND);
gl.blendFuncSeparate(gl.SRC_COLOR, gl.DST_COLOR, gl.ONE, gl.ZERO);

To get the current blend function, query the BLEND_SRC_RGB, BLEND_SRC_ALPHA, BLEND_DST_RGB, and BLEND_DST_ALPHA constants which return one of the blend function constants.

gl.enable(gl.BLEND);
gl.blendFuncSeparate(gl.SRC_COLOR, gl.DST_COLOR, gl.ONE, gl.ZERO);
gl.getParameter(gl.BLEND_SRC_RGB) == gl.SRC_COLOR;
// true

Specifications

Specification	Status	Comment
WebGL 1.0The definition of 'blendFunc' in that specification.	Recommendation	Initial definition. In WebGL, constant color and constant alpha cannot be used together as source and destination factors in the blend function. See section 6.13. of the specification.
OpenGL ES 2.0The definition of 'glBlendFunc' in that specification.	Standard	Man page of the OpenGL API.

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`blendFuncSeparate`	Chrome Full support 9	Edge Full support 12	Firefox Full support 4	IE Full support 11	Opera Full support 12	Safari Full support 5.1	WebView Android Full support Yes	Chrome Android Full support 25	Firefox Android Full support Yes	Opera Android Full support 12	Safari iOS Full support 8	Samsung Internet Android Full support 1.5
`SharedArrayBuffer` as a parameter	Chrome Full support 60	Edge Full support ≤79	Firefox Full support 79	IE ?	Opera Full support 47	Safari ?	WebView Android Full support 60	Chrome Android Full support 60	Firefox Android ?	Opera Android Full support 44	Safari iOS ?	Samsung Internet Android Full support 8.0

Legend

Full support: Full support
Compatibility unknown: Compatibility unknown