glClipPlane.3gl

Name

  glClipPlane -	specify	a plane	against	which all geometry is clipped

C Specification

  void glClipPlane( GLenum plane,

		    const GLdouble *equation )

Parameters

  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

	    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 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.

Notes

  It is	always the case	that GL_CLIP_PLANEi = 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 corresponding execution of glEnd.

Associated Gets

  glGetClipPlane

  glIsEnabled with argument GL_CLIP_PLANEi

See Also

  glEnable

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Last Edited: Mon, May 22, 1995

AFV