2 updated link to gluPerspective docs edited Jan 3 '16 at 8:09 michael.bartnett 7,09911 gold badge3030 silver badges4545 bronze badges The method in question (glm::perspective) and its ilk are essentially wrappers or re-implementations of gluPerspectivegluPerspective. As you can see from the documentation of that function, the near/far values are distances from the view plane, and are always positive. The method in question (glm::perspective) and its ilk are essentially wrappers or re-implementations of gluPerspective. As you can see from the documentation of that function, the near/far values are distances from the view plane, and are always positive. The method in question (glm::perspective) and its ilk are essentially wrappers or re-implementations of gluPerspective. As you can see from the documentation of that function, the near/far values are distances from the view plane, and are always positive. 1 answered May 26 '11 at 1:23 Josh♦ 94.6k1717 gold badges212212 silver badges330330 bronze badges The method in question (glm::perspective) and its ilk are essentially wrappers or re-implementations of gluPerspective. As you can see from the documentation of that function, the near/far values are distances from the view plane, and are always positive.