Index for Section 3G

Alphabetical listing for G

Bottom of page

glOrtho(3G)
NAME
  glOrtho - multiply the current matrix with an orthographic matrix

SYNOPSIS
  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 / 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
  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(3), glMatrixMode(3), glMultMatrix(3), glPushMatrix(3),
  glViewport(3)

Index for Section 3G

Alphabetical listing for G

Top of page