透视矩阵都是可逆的吗

Cocos2d-x
#1

为什么我这个相机的透视矩阵不可逆啊

Camera *camera = Camera::createPerspective(80, visibleSize.width / visibleSize.height, 0, 1);
this->addChild(camera);

camera->setPosition3D(Vec3(0, -680, 830) + Vec3(visibleSize.width / 2, visibleSize.height / 2, 0));
camera->lookAt(Vec3(visibleSize.width / 2, visibleSize.height /4, 0), Vec3(0, 1, 0));
camera->setCameraFlag(CameraFlag::USER1);