HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 314

O glOrtho glOrtho glOrtho: multiply the current matrix with an orthographic matrix. C Specification void glOrtho( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble zNear, GLdouble zFar) Parameters left, right bottom, top zNear, zFar 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 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: A 0 0 tx 0 B 0 ty 0 0 C tz 0 0 01 where A = 2 / (right left) B = 2 / (top bottom) C = 2 / (far near) tx = (right + left) / (right left) ty = (top + bottom) / (top bottom) tz = (zFar + zNear) / (zFar zNear) 314 Chapter 13