# Difference between revisions of "GLAPI/glViewport"

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Core in version 4.5 1.0

glViewport: set the viewport

## Function Definition

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 window, width​ and height​ are set to the dimensions of that window.

## Description

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:

$x_w = (x_{nd} + 1)\left ( \tfrac{width}{2} \right) + x$

$y_w = (y_{nd} + 1)\left ( \tfrac{height}{2} \right) + y$

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

## Errors

GL_INVALID_VALUE is generated if either width​ or height​ is negative.

## Associated Gets

with argument GL_VIEWPORT

with argument GL_MAX_VIEWPORT_DIMS

## Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.