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

Browser compatibility

[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

• WebGLRenderingContext.blendColor()
• WebGLRenderingContext.blendFunc()
• EXT_blend_minmax