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WebGLRenderingContext.blendEquation()

The WebGLRenderingContext.blendEquation() method of the WebGL API is used to set both the RGB blend equation and alpha blend equation to a single equation.

The blend equation determines how a new pixel is combined with a pixel already in the WebGLFramebuffer.

Syntax

void gl.blendEquation(mode);

Parameters

mode
A GLenum specifying how source and destination colors are combined. Must be either:
  • gl.FUNC_ADD: source + destination (default value),
  • gl.FUNC_SUBTRACT: source - destination,
  • gl.FUNC_REVERSE_SUBTRACT: destination - source
  • When using the EXT_blend_minmax extension:
    • ext.MIN_EXT: Minimum of source and destination,
    • ext.MAX_EXT: Maximum of source and destination.
  • When using a WebGL 2 context, the following values are available additionally:
    • gl.MIN: Minimum of source and destination,
    • gl.MAX: Maximum of source and destination.

Exception

If mode is not one of the three possible values, a gl.INVALID_ENUM error is thrown.

Return value

None.

Examples

To set the blend equation, use:

gl.blendEquation(gl.FUNC_ADD);
gl.blendEquation(gl.FUNC_SUBTRACT);
gl.blendEquation(gl.FUNC_REVERSE_SUBTRACT);

To get the blend equations, query the BLEND_EQUATION, BLEND_EQUATION_RGB and BLEND_EQUATION_ALPHA constants which return gl.FUNC_ADD, gl.FUNC_SUBTRACT, gl.FUNC_REVERSE_SUBTRACT, or if the EXT_blend_minmax is enabled: ext.MIN_EXT or ext.MAX_EXT.

gl.getParameter(gl.BLEND_EQUATION_RGB) === gl.FUNC_ADD;
// true

gl.getParameter(gl.BLEND_EQUATION_ALPHA) === gl.FUNC_ADD; 
// true

Specifications

Specification Status Comment
WebGL 1.0
The definition of 'blendEquation' in that specification.
Recommendation Initial definition for WebGL.
OpenGL ES 2.0
The definition of 'glBlendEquation' in that specification.
Standard Man page of the OpenGL ES 2.0 API.
OpenGL ES 3.0
The definition of 'glBlendEquation' in that specification.
Standard Man page of the OpenGL ES 3.0 API.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 9 12 4.0 (2.0) 11 12 5.1
WebGL 2 No support [2] No support Nightly build [1] No support No support No support
Feature Android Chrome for Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile
Basic support ? 25 4.0 (2.0) 1.0 ? 12 8.0
WebGL 2 No support No support No support No support No support No support No support

[1] WebGL 2 is enabled by default in Firefox Nightly. To enable it in a release version of Firefox, set the preference webgl.enable-prototype-webgl2 to true in about:config.

[2] To use an experimental implementation of WebGL 2 in Chrome, you have to start Chrome with the runtime flag --enable-unsafe-es3-apis.

See also

Document Tags and Contributors

 Contributors to this page: fscholz
 Last updated by: fscholz,