OpenGL man pages
glClipPlane - specify a plane against which all geometry is clipped
void glClipPlane( GLenum plane,
const GLdouble *equation )
plane Specifies which clipping plane is being positioned. 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
Geometry is always clipped against the boundaries of a six-plane frustum in
x, y, and z. glClipPlane allows the specification of additional planes, not
necessarily perpendicular to the x, y, or z axis, against which all
geometry is clipped. Up to GL_MAX_CLIP_PLANES planes can be specified,
where GL_MAX_CLIP_PLANES is at least six in all implementations. 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 coordinates 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.
Clipping planes are enabled and disabled with glEnable and glDisable, and
called with the argument GL_CLIP_PLANEi, where i is the plane number.
By default, all clipping planes are 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.
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 execution of glEnd.
glIsEnabled with argument GL_CLIP_PLANEi
Fri Dec 6 11:18:03 EST 1996
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