WebGLRenderingContext: stencilOp() 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.

Note: This feature is available inWeb Workers.

TheWebGLRenderingContext.stencilOp() method of theWebGL API sets both the front and back-facingstencil test actions.

Syntax

stencilOp(fail, zfail, zpass)

Parameters

fail: AGLenum specifying the function to use when the stencil test fails.The default value isgl.KEEP.
zfail: AGLenum specifying the function to use when the stencil test passes,but the depth test fails. The default value isgl.KEEP.
zpass: AGLenum specifying the function to use when both the stencil testand the depth test pass, or when the stencil test passes and there is no depth bufferor depth testing is disabled. The default value isgl.KEEP.

Return value

None (undefined).

Constants

gl.KEEP: Keeps the current value.
gl.ZERO: Sets the stencil buffer value to 0.
gl.REPLACE: Sets the stencil buffer value to the reference value as specified byWebGLRenderingContext.stencilFunc().
gl.INCR: Increments the current stencil buffer value. Clamps to the maximum representableunsigned value.
gl.INCR_WRAP: Increments the current stencil buffer value. Wraps stencil buffer value to zero whenincrementing the maximum representable unsigned value.
gl.DECR: Decrements the current stencil buffer value. Clamps to 0.
gl.DECR_WRAP: Decrements the current stencil buffer value. Wraps stencil buffer value to themaximum representable unsigned value when decrementing a stencil buffer value of 0.
gl.INVERT: Inverts the current stencil buffer value bitwise.

Examples

The stencil testing is disabled by default. To enable or disable stencil testing, usetheenable() anddisable() methods with the argumentgl.STENCIL_TEST.

gl.enable(gl.STENCIL_TEST);gl.stencilOp(gl.INCR, gl.DECR, gl.INVERT);

To get the current information about stencil and depth pass or fail, query thefollowing constants withgetParameter().

gl.getParameter(gl.STENCIL_FAIL);gl.getParameter(gl.STENCIL_PASS_DEPTH_PASS);gl.getParameter(gl.STENCIL_PASS_DEPTH_FAIL);gl.getParameter(gl.STENCIL_BACK_FAIL);gl.getParameter(gl.STENCIL_BACK_PASS_DEPTH_PASS);gl.getParameter(gl.STENCIL_BACK_PASS_DEPTH_FAIL);gl.getParameter(gl.STENCIL_BITS);