man glViewportArray (3): set multiple viewports

C SPECIFICATION

void glViewportArrayv(GLuint first, GLsizei count, const GLfloat *v);

PARAMETERS

first

: Specify the first viewport to set.

count

: Specify the number of viewports to set.

: Specify the address of an array containing the viewport parameters.

DESCRIPTION

glViewportArrayv specifies the parameters for multiple viewports simulataneously. first specifies the index of the first viewport to modify and count specifies the number of viewports to modify. first must be less than the value of GL_MAX_VIEWPORTS, and first + count must be less than or equal to the value of GL_MAX_VIEWPORTS. Viewports whose indices lie outside the range [first, first + count) are not modified. 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.

ERRORS

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

GL_INVALID_VALUE is generated if first + count 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

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