glOrtho

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 near_val,
		     GLdouble far_val )


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.

       near_val, far_val
		   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 projec-
       tion.  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	    tx



















			 0	__________	   0	    ty









		    (					      )









			 0	    0	   ________________ tz



















			 0	    0		  0	    1

       where
				   tx=−__________

				   ty=−__________

				tz=−________________


Typically, the matrix mode is GL_PROJECTION, and (left,	 bottom,   -near_val)
and  (right,  top,   -near_val) 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_val speci-
fies the location of the far clipping plane.  Both near_val and	 far_val  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(3G),  glMatrixMode(3G),  glMultMatrix(3G), glPushMatrix(3G),
       glViewport(3G)



								  GLORTHO(3G)