- set the viewport



C SPECIFICATION


PARAMETERS

       _param1, _param2 Specify  the  lower  left  corner  of the
                        viewport rectangle, in pixels.  The  ini-
                        tial value is (0,0).

       _param3, _param4 Specify the width and height of the view-
                        port.   When  a  GL  context   is   first
                        attached to a window, _param3 and _param4
                        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:

                   xw=(xnd+1)(_e_q_n_p_a_r_a_m__)+_eqnparam1

                   yw=(ynd+1)(_e_q_n_p_a_r_a_m__)+_eqnparam2

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 _param3 or _param4
       is negative.

       GL_INVALID_OPERATION  is  generated  if glViewport is exe-
       cuted between the execution of glBegin and the correspond-
       ing execution of glEnd.




















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