HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 315

O glOrtho 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_MODELVIEW_MATRIX glGet with argument GL_PROJECTION_MATRIX glGet with argument GL_TEXTURE_MATRIX See Also glFrustum, glMatrixMode, glMultMatrix, glPushMatrix, glViewport Chapter 13 315