glViewport — set the viewport

C Specification

void glViewport(GLint x,
 GLint y,
 GLsizei width,
 GLsizei height);


x, y

Specify the lower left corner of the viewport rectangle, in pixels. The initial value is (0, 0).

width, height

Specify the width and height of the viewport. When a GL context is first attached to a surface (e.g. window), width and height are set to the dimensions of that surface.


glViewport specifies the affine transformation of x and y from normalized device coordinates to window coordinates. Let xnd ynd be normalized device coordinates. Then the window coordinates xw yw are computed as follows:

xw = ( xnd + 1 ) width 2 + x yw = ( ynd + 1 ) height 2 + y

Viewport width and height are silently clamped to a range that depends on the implementation. To query this range, call glGet with argument GL_MAX_VIEWPORT_DIMS.


GL_INVALID_VALUE is generated if either width or height is negative.

Associated Gets

glGet with argument GL_MAX_VIEWPORT_DIMS

See Also

glDepthRange, glGet


Copyright © 2003-2004 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see