glViewport — set the viewport

C Specification

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.


glViewport specifies the affine transformation of x and y from normalized device coordinates to window coordinates. Let x nd y nd be normalized device coordinates. Then the window coordinates x w y w are computed as follows:

x w = x nd + 1 width 2 + x

y w = y nd + 1 height 2 + 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.


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

See Also



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