HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 321

P gluPerspective gluPerspective gluPerspective: set up a perspective projection matrix. C Specification void gluPerspective( GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar) Parameters fovy aspect zNear zFar Specifies the field of view angle, in degrees, in the Y direction. Specifies the aspect ratio that determines the field of view in the X direction. The aspect ratio is the ratio of X (width) to Y (height). Specifies the distance from the viewer to the near clipping plane (always positive). Specifies the distance from the viewer to the far clipping plane (always positive). Description gluPerspective specifies a viewing frustum into the world coordinate system. In general, the aspect ratio in gluPerspective should match the aspect ratio of the associated viewport. For example, aspect = 2.0 means the viewer's angle of view is twice as wide in X as it is in Y. If the viewport is twice as wide as it is tall, it displays the image without distortion. The matrix generated by gluPerspective is multiplied by the current matrix, just as if glMultMatrix were called with the generated matrix. To load the perspective matrix onto the current matrix stack instead, precede the call to gluPerspective with a call to glLoadIdentity. Given f defined as cotangent(fovy / 2), the generated matrix is A000 0f 00 0 0 BC 0 0 -1 0 where: A = f / aspect B = (zFar + zNear) / (zNear - zFar) C = (2 × zFar × zNear) / (zNear × zFar) Chapter 14 321