The other means of constructing protocol code for the asyncio framework is to construct a ( ), which is a function that pauses when it wants to perform I/O.
【单选题】If a surface on an object is parallel to one of the principal planes of projection, then the angular relationship of that surface to at least two other principal projection planes is:
【简答题】The intersection points of the two principal planes and the axis are called , in object space ----- the principal point H in image space -------the principal point H’ H and H’ are