WebGLRenderingContext: stencilFunc() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

See full compatibility

Note: This feature is available in Web Workers.

The WebGLRenderingContext.stencilFunc() method of the WebGL API sets the front and back function and reference value for stencil testing.

Stenciling enables and disables drawing on a per-pixel basis. It is typically used in multipass rendering to achieve special effects.

Syntax

stencilFunc(func, ref, mask)

Parameters

func

A GLenum specifying the test function. The default function is gl.ALWAYS. The possible values are:

gl.NEVER: Never pass.
gl.LESS: Pass if (ref & mask) < (stencil & mask).
gl.EQUAL: Pass if (ref & mask) = (stencil & mask).
gl.LEQUAL: Pass if (ref & mask) <= (stencil & mask).
gl.GREATER: Pass if (ref & mask) > (stencil & mask).
gl.NOTEQUAL: Pass if (ref & mask) !== (stencil & mask).
gl.GEQUAL: Pass if (ref & mask) >= (stencil & mask).
gl.ALWAYS: Always pass.

ref

A GLint specifying the reference value for the stencil test. This value is clamped to the range 0 to 2^n - 1 where n is the number of bitplanes in the stencil buffer. The default value is 0.

mask

A GLuint specifying a bit-wise mask that is used to AND the reference value and the stored stencil value when the test is done. The default value is all 1.

Return value

None (undefined).

Examples

The stencil testing is disabled by default. To enable or disable stencil testing, use the enable() and disable() methods with the argument gl.STENCIL_TEST.

gl.enable(gl.STENCIL_TEST);
gl.stencilFunc(gl.LESS, 0, 0b1110011);

To get the current stencil function, reference value, or other stencil information, query the following constants with getParameter().

gl.getParameter(gl.STENCIL_FUNC);
gl.getParameter(gl.STENCIL_VALUE_MASK);
gl.getParameter(gl.STENCIL_REF);
gl.getParameter(gl.STENCIL_BACK_FUNC);
gl.getParameter(gl.STENCIL_BACK_VALUE_MASK);
gl.getParameter(gl.STENCIL_BACK_REF);
gl.getParameter(gl.STENCIL_BITS);

Specifications

Specification
WebGL Specification # 5.14.3

Browser compatibility

	desktop					mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS
`stencilFunc`	Chrome – Full support Chrome 9 (Release date: 2011-02-03) footnote Full support	Edge – Full support Edge 12 (Release date: 2015-07-29) footnote Full support	Firefox – Full support Firefox 4 (Release date: 2011-03-22) footnote Full support	Opera – Full support Opera 12 (Release date: 2012-06-14) footnote Full support	Safari – Full support Safari 5.1 (Release date: 2011-07-20) footnote Full support	Chrome Android – Full support Chrome Android 25 (Release date: 2013-02-27) footnote Full support	Firefox for Android – Full support Firefox for Android 4 (Release date: 2011-03-29) footnote Full support	Opera Android – Full support Opera Android 12 (Release date: 2012-02-25) footnote Full support	Safari on iOS – Full support Safari on iOS 8 (Release date: 2014-09-17) footnote Full support	Samsung Internet – Full support Samsung Internet 1.5 (Release date: 2013-09-25) footnote Full support	WebView Android – Full support WebView Android 4.4.3 (Release date: 2014-06-02) footnote Full support	WebView on iOS – Full support WebView on iOS 8 (Release date: 2014-09-17) footnote Full support

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Full support: Full support