I would just like to officially confirm that objects off-screen are not rendered at all. This seems to be such a common misconception I think I'll add it to the manual.
For the record, here's how it really works:
- if any part of an object is on-screen, the CPU issues a command to tell the GPU to draw it. If it's offscreen, the GPU never even knows it exists.
- the GPU only draws objects that are on-screen, but is still smart enough to only draw part of an image if it goes offscreen. So if you have a tiled background the size of your layout, the GPU knows only to draw the part of it that is in the window. So off-screen content is still not rendered.
- even if Construct 2 issued draw commands for objects that are off-screen, the GPU is smart enough to just completely ignore it, because it can tell it doesn't appear in the window. However this is a waste of CPU time issuing a pointless draw call, so pretty much every engine that has ever existed will simply not issue draw calls for stuff that is off-screen.
You could probably measure a really tiny performance impact from having lots of objects off-screen (like, tens of thousands). This is only because Construct 2 is checking if they are off-screen and then deciding to ignore them, which is such a tiny amount of work it usually doesn't factor in to the framerate at all. But they're definitely not being drawn.