WebGLRenderingContext.scissor

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

Syntax

void gl.scissor(x, y, width, height);

Parameters

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.

Return value

None.

Errors thrown

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

Examples

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]

Specifications

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

Browser compatibility

See also

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