## Name

glViewportIndexed — set a specified viewport

## C Specification

`void glViewportIndexedf(` | GLuint index,
| GLfloat x,
| GLfloat y,
| GLfloat w,
| GLfloat h`)`;

`void glViewportIndexedfv(` | GLuint index,
| const GLfloat *v`)`;

## Parameters

`index`

  Specify the first viewport to set.

`x`, `y`

  For `glViewportIndexedf`, specifies the lower left corner of the viewport rectangle, in pixels. The initial value is (0,0).

`width`, `height`

  For `glViewportIndexedf`, specifies 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.

`v`

  For `glViewportIndexedfv`, specifies the address of an array containing the viewport parameters.

## Description

`glViewportIndexedf` and `glViewportIndexedfv` specify the parameters for a single viewport. `index` specifies the index of the viewport to modify. `index` must be less than the value of `GL_MAX_VIEWPORTS`. For `glViewportIndexedf`, `x`, `y`, `w`, and `h` specify the left, bottom, width and height of the viewport in pixels, respectively. For `glViewportIndexedfv`, `v` contains the address of an array of floating point values specifying the left (x), bottom (y), width (w), and height (h) of each viewport, in that order. x and y give the location of the viewport's lower left corner, and w and h give the width and height of the viewport, respectively. The viewport 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

The location of the viewport's bottom left corner, given by (x, y) is clamped to be within the implementaiton-dependent viewport bounds range. The viewport bounds range [min, max] can be determined by calling glGet with argument `GL_VIEWPORT_BOUNDS_RANGE`. 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`.

The precision with which the GL interprets the floating point viewport bounds is implementation-dependent and may be determined by querying the impementation-defined constant `GL_VIEWPORT_SUBPIXEL_BITS`.

Calling `glViewportIndexedfv` is equivalent to calling glViewportArray with `first` set to `index`, `count` set to 1 and `v` passsed directly. `glViewportIndexedf` is equivalent to:

        void glViewportIndexedf(GLuint index, GLfloat x, GLfloat y, GLfloat w, GLfloat h)
        {
            const float v[4]  = { x, y, w, h };
            glViewportArrayv(index, 1, v);
        }

## Errors

`GL_INVALID_VALUE` is generated if `index` is greater than or equal to the value of `GL_MAX_VIEWPORTS`.

`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`

glGet with argument `GL_VIEWPORT_BOUNDS_RANGE`

glGet with argument `GL_VIEWPORT_SUBPIXEL_BITS`

## See Also

glDepthRange, glViewport, glViewportArray

## Copyright

Copyright © 2010 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.