The glOrtho function multiplies the current matrix by an orthographic matrix.
void glOrtho(
GLdouble left,
GLdouble right,
GLdouble bottom,
GLdouble top,
GLdouble near,
GLdouble far
);
The glOrtho function describes a perspective matrix that produces a parallel projection. The (left, bottom, – near) and (right, top, – near) parameters 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). The –far parameter specifies the location of the far clipping plane. Both near and far can be either positive or negative. The corresponding matrix is
where
The current matrix is multiplied by this matrix with the result replacing the current matrix. That is, if M is the current matrix and O is the ortho matrix, then M is replaced with M · O.
Use glPushMatrix and glPopMatrix to save and restore the current matrix stack.
The following functions retrieve information related to glOrtho:
glGet with argument GL_MATRIX_MODE
glGet with argument GL_MODELVIEW_MATRIX
glGet with argument GL_PROJECTION_MATRIX
glGet with argument GL_TEXTURE_MATRIX
The following are the error codes generated and their conditions.
Error Code | Condition |
---|---|
GL_INVALID_OPERATION | glOrtho was called between a call to glBegin and the corresponding call to glEnd. |
Windows NT: Use version 3.5 and later.
Windows: Use Windows 95 and later.
Windows CE: Unsupported.
Header: Declared in gl.h.
Import Library: Link with opengl32.lib.
glBegin, glEnd, glFrustum, glMatrixMode, glMultMatrix, glPushMatrix, glViewport