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

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 (undefined).

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
WebGL Specification
# 5.14.3

Browser compatibility

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See also