WebGLRenderingContext.blendEquationSeparate

The WebGLRenderingContext.blendEquationSeparate() method of the WebGL API is used to set the RGB blend equation and alpha blend equation separately.

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

Syntax

void gl.blendEquationSeparate(modeRGB, modeAlpha);

Parameters

modeRGB

A GLenum specifying how the red, green and blue components of 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.

modeAlpha

A GLenum specifying how the alpha component (transparency) of 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.

Return value

None.

Exceptions

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

Examples

To set the blend equations, use:

gl.blendEquationSeparate(gl.FUNC_ADD, gl.FUNC_SUBTRACT);

To get the current 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 'blendEquationSeparate' in that specification.	Recommendation	Initial definition for WebGL.
OpenGL ES 2.0 The definition of 'glBlendEquationSeparate' in that specification.	Standard	Man page of the OpenGL ES 2.0 API.
OpenGL ES 3.0 The definition of 'glBlendEquationSeparate' in that specification.	Standard	Man page of the OpenGL ES 3.0 API.

Browser compatibility

See also

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