MirOS Manual: glOrtho(3)


GLORTHO(3G)         UNIX Programmer's Manual          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
     projection. The current matrix (see glMatrixMode) is multi-
     plied by this matrix and the result replaces the current
     matrix, as if glMultMatrix were called with the following
     matrix as its argument:
           |
           |
           |
           |__________
           |right-left      0
           |                               0
           |    0       __________                       |
           |            top-bottom         0          tx |
           |    0                                        |
           |    0           0       ________2________  ty |
                            0       far_val-near_val     |
                                           0          tz |
                                                      1  |
                                                         |
                                                         |
                                                         |

     where                      _i__h___±__e__t_
                          tx = -t_o_p__t±_b__l_t_o_m_
                          ty f__-___v_a__-_±_o_e_a_r____a__l
                       tz = -far_val - near_val

MirOS BSD #10-current  Printed 03.04.2017                       1

GLORTHO(3G)         UNIX Programmer's Manual          GLORTHO(3G)

     Typically, the matrix mode is GL_PROJECTION, and (left, bot-
     tom,  -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, respec-
     tively, assuming that the eye is located at (0, 0, 0).
     -far_val specifies the location of the far clipping plane.
     Both near_val and far_val can be either positive or nega-
     tive.

     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 exe-
     cution 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)

MirOS BSD #10-current  Printed 03.04.2017                       2

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