WebGLRenderingContext: blendEquation() method

{{APIRef("WebGL")}}{{AvailableInWorkers}}

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 {{domxref("WebGLFramebuffer")}}.

Syntax

blendEquation(mode)

Parameters

• mode

  • : A {{domxref("WebGL_API/Types", "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 {{domxref("EXT_blend_minmax")}} extension:

    • ext.MIN_EXT: Minimum of source and destination
    • ext.MAX_EXT: Maximum of source and destination

    When using a {{domxref("WebGL2RenderingContext", "WebGL 2 context", "", 1)}}, the following values are available additionally:

    • gl.MIN: Minimum of source and destination
    • gl.MAX: Maximum of source and destination

Exceptions

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

Return value

None ({{jsxref("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 {{domxref("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

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{domxref("WebGLRenderingContext.blendColor()")}}
• {{domxref("WebGLRenderingContext.blendFunc()")}}
• {{domxref("EXT_blend_minmax")}}