# Difference between revisions of "GLAPI/glViewport"

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 glGet with argument GL_MAX_VIEWPORT_DIMS​.

## Errors

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

## Associated Gets

glGet with argument GL_VIEWPORT​

glGet with argument GL_MAX_VIEWPORT_DIMS​