The WebGLRenderingContext.scissor() method of the WebGL API sets a scissor box, which limits the drawing to a specified rectangle.

x

A GLint specifying the horizontal coordinate for the lower left corner of the box. Default value: 0.

y

A GLint specifying the vertical coordinate for the lower left corner of the box. Default value: 0.

width

A non-negative GLsizei specifying the width of the scissor box. Default value: width of the canvas.

height

A non-negative GLsizei specifying the height of the scissor box. Default value: height of the canvas.

None (undefined).

If either width or height is a negative value, a gl.INVALID_VALUE error is thrown.

When the scissor test is enabled, only pixels within the scissor box can be modified by drawing commands.

// turn on scissor test
gl.enable(gl.SCISSOR_TEST);

// set the scissor rectangle
gl.scissor(x, y, width, height);

// execute drawing commands in the scissor box (e.g. clear)

// turn off scissor test again
gl.disable(gl.SCISSOR_TEST);

To get the current scissor box dimensions, query the SCISSOR_BOX constant which returns an Int32Array.

gl.scissor(0, 0, 200, 200);
gl.getParameter(gl.SCISSOR_BOX);
// Int32Array[0, 0, 200, 200]

• WebGLRenderingContext.viewport()
• WebGLRenderingContext.enable()
• WebGLRenderingContext.disable()