Web/API/WebGLRenderingContext/stencilFunc

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

void gl.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 2ⁿ -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.

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	Status	Comment
WebGL 1.0The definition of 'stencilFunc' in that specification.	Recommendation	Initial definition.
OpenGL ES 2.0The definition of 'glStencilFunc' in that specification.	Standard	Man page of the OpenGL API.

Browser compatibility

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.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`stencilFunc`	Chrome Full support 9	Edge Full support 12	Firefox Full support 4	IE Full support 11	Opera Full support 12	Safari Full support 5.1	WebView Android Full support Yes	Chrome Android Full support 25	Firefox Android Full support Yes	Opera Android Full support 12	Safari iOS Full support 8	Samsung Internet Android Full support 1.5

Legend

Full support: Full support