'''_glViewport:''' set the viewport


{{PageSyntax}}

  SUB _glViewport (BYVAL x AS LONG, BYVAL y AS LONG, BYVAL width AS LONG, BYVAL height AS LONG)
  void '''_glViewport'''(GLint {{Parameter|x}}, GLint {{Parameter|y}}, GLsizei {{Parameter|width}}, GLsizei {{Parameter|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, {{Parameter|width}} and {{Parameter|height}} are set to the dimensions of that window.


{{PageDescription}}

'''_glViewport''' specifies the affine transformation of ''x'' and ''y'' from normalized device coordinates to window coordinates. Let (x&amp;lt;sub&amp;gt;nd&amp;lt;/sub&amp;gt;, y&amp;lt;sub&amp;gt;nd&amp;lt;/sub&amp;gt;) be normalized device coordinates. Then the window coordinates (x&amp;lt;sub&amp;gt;w&amp;lt;/sub&amp;gt;, y&amp;lt;sub&amp;gt;w&amp;lt;/sub&amp;gt;) are computed as follows:

{{glapi viewport equations}}

Viewport width and height are silently clamped to a range that depends on the implementation. To query this range, call {{KW|_glGet}} with argument {{KW|_GL_MAX_VIEWPORT_DIMS}}.


{{PageErrors}}

{{KW|_GL_INVALID_VALUE}} is generated if either {{Parameter|width}} or {{Parameter|height}} is negative.


{{PageUseWith}}

{{KW|_glGet}} with argument {{KW|_GL_VIEWPORT}}

{{KW|_glGet}} with argument {{KW|_GL_MAX_VIEWPORT_DIMS}}


{{PageSeeAlso}}

[[_GL|SUB _GL]]
{{KW|_glDepthRange}}, {{KW|_glViewportArray}}, {{KW|_glViewportIndexed}}


{{PageCopyright}}

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/ http://oss.sgi.com/projects/FreeB/].
