GLCLIPPLANE() MachTen Programmer’s Manual GLCLIPPLANE()

NAME
glClipPlane - specify a plane against which all geometry
is clipped

C SPECIFICATION
void glClipPlane( GLenum plane,
const GLdouble *equation )

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PARAMETERS
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 dou-
ble-precision floating-point values. These val-
ues are interpreted as a plane equation.

DESCRIPTION
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 per-
pendicular to the x, y, or z axis, against which all geom-
etry is clipped. To determine the maximum number of addi-
tional clipping 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 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.

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.

NOTES
It is always the case that GL_CLIP_PLANE$i$ =
GL_CLIP_PLANE0 + $i$.

ERRORS
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 corre-
sponding execution of glEnd.

ASSOCIATED GETS
glGetClipPlane
glIsEnabled with argument GL_CLIP_PLANEi