in my scene I implemented a nice tree alley - quite a complex beast… (-;
Now when it comes to rendering the animation, things are nice when I do not activate my tree alley to be rendered. When I include it into the objects to be rendered, that slows down the whole process dramatically from the first frame, allthough in the first half of the scene the trees are not visible, because they are not in the focus of my cameras.
The fact that something is not visible does not mean that it does not influence the scene. It can still cast shadows, bounce or generate light etc. What the influence is is not known beforehand to render engine, so it can’t discard come object just because it is not in the view.
If you know that removing the alley does not affect the rest of the scene, remove it for the part where it is not visible and include it in render where it is.