glOrtho(3G)		       OpenGL Reference			   glOrtho(3G)

NAME    [Toc]    [Back]

     glOrtho - multiply	the current matrix with	an orthographic	matrix

C SPECIFICATION    [Toc]    [Back]

     void glOrtho( GLdouble left,
		   GLdouble right,
		   GLdouble bottom,
		   GLdouble top,
		   GLdouble near,
		   GLdouble far	)

PARAMETERS    [Toc]    [Back]

     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.

     near, far	 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    [Toc]    [Back]

     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:





		      (					    )
		       __________
		      |		       0	  0	 t  |
		       right-left			  x
		      |					    |

		      |		   __________		    |
			   0			  0	 t
		      |		   top-bottom		  y |

		      |					    |
					       ________
		      |	   0	       0		 t  |
					       far-near	  z
		      |					    |

		      |	   0	       0	  0	 1  |

		      (					    )

     where
				      ____________
				t  = -
				 x    right - left

				      ____________
				t  = -
				 y    top - bottom

				       __________
				 t  = -
				  z    far - near



     Typically,	the matrix mode	is GL_PROJECTION, and (left, bottom,  -near)
     and (right, top,  -near) 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).  -far



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glOrtho(3G)		       OpenGL Reference			   glOrtho(3G)



     specifies the location of the far clipping	plane.	Both near and far can
     be	either positive	or negative.

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

ERRORS    [Toc]    [Back]

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

ASSOCIATED GETS    [Toc]    [Back]

     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    [Toc]    [Back]

     glFrustum,	glMatrixMode, glMultMatrix, glPushMatrix, glViewport


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