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

See also

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