glclipplane(3g) [suse man page]

GLCLIPPLANE(3G) 														   GLCLIPPLANE(3G)

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  equa-
		 tion.

DESCRIPTION

       Geometry  is  always  clipped  against the boundaries of a six-plane frustum in x, y, and z.  glClipPlane allows the specification of addi-
       tional planes, not necessarily perpendicular to the x, y, or z axis, against which all geometry is clipped.  To determine the maximum  num-
       ber of additional clipping planes, call glGetIntegerv with argument GL_MAX_CLIP_PLANES. All implementations support at least six such clip-
       ping 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_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(3G)

																   GLCLIPPLANE(3G)

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GLORTHO(3G)															       GLORTHO(3G)

NAME

       glOrtho - multiply the current matrix with an orthographic matrix

C SPECIFICATION

       void glOrtho( GLdouble left,
		     GLdouble right,
		     GLdouble bottom,
		     GLdouble top,
		     GLdouble zNear,
		     GLdouble zFar )

PARAMETERS

       left, right Specify the coordinates for the left and right vertical clipping planes.

       bottom, top Specify the coordinates for the bottom and top horizontal clipping planes.

       zNear, zFar Specify  the distances to the nearer and farther depth clipping planes.  These values are negative if the plane is to be behind
		   the viewer.

DESCRIPTION

       glOrtho describes a transformation that produces a parallel projection.	The current matrix (see glMatrixMode) is multiplied by this matrix
       and the result replaces the current matrix, as if glMultMatrix were called with the following matrix as its argument:

	      2
	------------	   0		  0		 tx
	right - left

			   2
	    0	      ------------	  0		 ty
		      top - bottom

					  -2
	    0		   0	     ------------	 tz
				      zFar-zNear

	    0		   0		  0		 1

       where

							 tx = - (right + left) / (right - left)

							 ty = - (top + bottom) / (top - bottom)

							 tz = - (zFar + zNear) / (zFar - zNear)

       Typically,  the matrix mode is GL_PROJECTION, and (left, bottom,  -zNear) and (right, top,  -zNear) specify the points on the near clipping
       plane that are mapped to the lower left and upper right corners of the window, respectively, assuming that the eye is located at (0, 0, 0).
       -zFar specifies the location of the far clipping plane.	Both zNear and zFar can be either positive or negative.

       Use glPushMatrix and glPopMatrix to save and restore the current matrix stack.

ERRORS

       GL_INVALID_OPERATION is generated if glOrtho is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

       glGet with argument GL_MATRIX_MODE
       glGet with argument GL_COLOR_MATRIX
       glGet with argument GL_MODELVIEW_MATRIX
       glGet with argument GL_PROJECTION_MATRIX
       glGet with argument GL_TEXTURE_MATRIX

SEE ALSO

       glFrustum, glMatrixMode, glMultMatrix, glPushMatrix, glViewport

																       GLORTHO(3G)

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