2. In CS of "iPortal" interface, it provides a function of "virtual const csPlane3 & GetObjectPlane ()=0 " , the description of it is "Get the object space plane of this portal", what does it mean of "object space plane "? Does it mean "object space"?
A portal is a polygon. The vertices of this polygon lie on a plane, the portal plane
. And yes, "object space" means that plane is in object space. (Portals have, like mesh objects, an object-to-world transform).
3. I want to get the vertex coordinate in world space of a portal which is in the game world, but i don't know which function to use in "iPortal" to get the portal's vertex coordinate?
The is no "the" vertex coordinate, there are more than one vertex in a portal. iPortal has GetVertex*() and GetVertices*() methods you can use to access the vertices of a portal.
4. In CS, the portal is rendering the contents of that other sector as seen through this portal, so if i want to get this content how can I do, or which function can i use to get it? And Is the content which i get a picture or anything else?
What do you mean? The contents of the portal are rendered to the screen.
If you want these contents on a texture or so you need to use some rendering to a texture.