glScissor -- define the scissor box


void glScissor(GLint x,
               GLint y,
               GLsizei width,
               GLsizei height)


x, y
Specify the lower left corner of the scissor box. Initially (0, 0).

width, height
Specify the width and height of the scissor box. When a GL context is first attached to a window, width and height are set to the dimensions of that window.


The glScissor routine defines a rectangle, called the scissor box, in window coordinates. The first two arguments, x and y, specify the lower left corner of the box. width and height specify the width and height of the box.

The scissor test is enabled and disabled using glEnable and glDisable with argument GL_SCISSOR_TEST. While the scissor test is enabled, only pixels that lie within the scissor box can be modified by drawing commands. Window coordinates have integer values at the shared corners of frame buffer pixels, so glScissor(0, 0, 1, 1) allows only the lower left pixel in the window to be modified, and glScissor(0, 0, 0, 0) disallows modification to all pixels in the window.

When the scissor test is disabled, it is as though the scissor box includes the entire window.


GL_INVALID_VALUE is generated if either width or height is negative.

GL_INVALID_OPERATION is generated if glScissor is called between a call to glBegin and the corresponding call to glEnd.


glGet with argument GL_SCISSOR_BOX
glIsEnabled with argument GL_SCISSOR_TEST


glEnable, glViewport

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© 1995 Uwe Behrens. All rights reserved.