WebGLRenderingContext.blendEquationSeparate() - Web API 接口参考 编辑

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

Browser compatibility

BCD tables only load in the browser

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

See also

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