NAME    [Toc]    [Back]

       glOrtho - multiply the current matrix with an orthographic
       matrix

SYNOPSIS    [Toc]    [Back]

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

PARAMETERS    [Toc]    [Back]

       Specify the coordinates for the left  and  right  vertical
       clipping  planes.   Specify the coordinates for the bottom
       and top horizontal clipping planes.  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:  2  /  right-left
       0            0             t[x]  0                    2  /
       top-bottom             0                    t[y]         0
       0     -2 / zFar - zNear   t[z] 0                         0
       0            1

       where  t[x] = - right + left / right - left t[y] = - top +
       bottom / top - bottom t[z] = 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    [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(3),  glMatrixMode(3), glMultMatrix(3), glPushMatrix(3), glViewport(3)



                                                      glOrtho(3G)