- define the scissor box
C SPECIFICATION
PARAMETERS
_param1, _param2 Specify the lower left corner of the
scissor box. Initially (0, 0).
_param3, _param4 Specify the width and height of the scis-
sor box. When a GL context is first
attached to a window, _param3 and _param4
are set to the dimensions of that window.
DESCRIPTION
glScissor defines a rectangle, called the scissor box, in
window coordinates. The first two arguments, _param1 and
_param2, specify the lower left corner of the box.
_param3 and _param4 specify the width and height of the
box.
To enable and disable the scissor test, call glEnable and
glDisable with argument GL_SCISSOR_TEST. The test is ini-
tially disabled. While the test is enabled, only pixels
that lie within the scissor box can be modified by drawing
commands. Window coordinates have integer values at the
shared corners of frame buffer pixels. glScissor(0,0,1,1)
allows modification of only the lower left pixel in the
window, and glScissor(0,0,0,0) doesn't allow modification
of any pixels in the window.
When the scissor test is disabled, it is as though the
scissor box includes the entire window.
ERRORS
GL_INVALID_VALUE is generated if either _param3 or _param4
is negative.
GL_INVALID_OPERATION is generated if glScissor is executed
between the execution of glBegin and the corresponding
execution of glEnd.
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