GLCLIPPLANE(3G) UNIX Programmer's Manual GLCLIPPLANE(3G)
glClipPlane - specify a plane against which all geometry is
clipped
void glClipPlane( GLenum plane,
const GLdouble *equation )
plane Specifies which clipping plane is being posi-
tioned. Symbolic names of the form GL_CLIP_PLANEi,
where i is an integer between 0 and
GL_MAX_CLIP_PLANES-1, are accepted.
equation Specifies the address of an array of four double-
precision floating-point values. These values are
interpreted as a plane equation.
Geometry is always clipped against the boundaries of a six-
plane frustum in x, y, and z. glClipPlane allows the specif-
ication of additional planes, not necessarily perpendicular
to the x, y, or z axis, against which all geometry is
clipped. To determine the maximum number of additional clip-
ping planes, call glGetIntegerv with argument
GL_MAX_CLIP_PLANES. All implementations support at least six
such clipping planes. Because the resulting clipping region
is the intersection of the defined half-spaces, it is always
convex.
glClipPlane specifies a half-space using a four-component
plane equation. When glClipPlane is called, equation is
transformed by the inverse of the modelview matrix and
stored in the resulting eye coordinates. Subsequent changes
to the modelview matrix have no effect on the stored plane-
equation components. If the dot product of the eye coordi-
nates of a vertex with the stored plane equation components
is positive or zero, the vertex is in with respect to that
clipping plane. Otherwise, it is out.
To enable and disable clipping planes, call glEnable and
glDisable with the argument GL_CLIP_PLANEi, where i is the
plane number.
All clipping planes are initially defined as (0, 0, 0, 0) in
eye coordinates and are disabled.
It is always the case that GL_CLIP_PLANEi =
GL_CLIP_PLANE0 + i.
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GLCLIPPLANE(3G) UNIX Programmer's Manual GLCLIPPLANE(3G)
GL_INVALID_ENUM is generated if plane is not an accepted
value.
GL_INVALID_OPERATION is generated if glClipPlane is executed
between the execution of glBegin and the corresponding exe-
cution of glEnd.
glGetClipPlane
glIsEnabled with argument GL_CLIP_PLANEi
glEnable(3G)
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