GLVIEWPORT

Section: Misc. Reference Manual Pages (3G)
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NAME

glViewport - set the viewport

C SPECIFICATION

void glViewport( GLint x,


                   GLint y,
                   GLsizei width,
                   GLsizei height )

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PARAMETERS

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 ($x sub nd$, $y sub nd$) be normalized device coordinates. Then the window coordinates ($x sub w$, $y sub w$) are computed as follows:

x sub w ~=~ ( x sub nd ~+~ 1 ) left ( "width" over 2 right ) ~+~ "x"

y sub w ~=~ ( y sub nd ~+~ 1 ) left ( "height" over 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. GL_INVALID_OPERATION is generated if glViewport is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

glGet with argument GL_VIEWPORT
glGet with argument GL_MAX_VIEWPORT_DIMS