Simple Q. When you create a lightmass portal, you are given a rectangle. Are you supposed to put that rectangle on every window opening or are you supposed to grow the rectangle to the size of the room and put it inside the room? Bit confused by it.
Put it in any opening allowing light in.
do you have to shape it to the openings dimensions? or it can over lap? I loaded a default level with nothing but the standard outside light. I put a interior with 4 rooms and 3 windows. Do i put it in all doorways and windows?
It can overlap, doesn’t have to be exact, just generally covering the window opening.
You don’t want to make big portals and you don’t want to place them everywhere - that will make your build times horrible. Just place them over openings where most of the skylight is coming in.
can correct me on this, but the idea of the portals is to focus more photons on that area. So the bigger the portal, the more photons generated, the longer your build times. So you want to make them as small as you can while still covering the openings you need them to.
ahh ok. and do the doorways need them too? like the interior room doorways? or just the main door to the outside environment?
No, I don’t think there’s any reason to use them inside a building. I think if you put one inside, it would just lead to the extra photons bouncing off the roof of the building above wherever the door is.
Makes sense. Thxs for the input. 
For interior scenes with sunlit windows (common scenario) are portals a must, or are they only when you’re not getting enough light?
thanks.
Portals increase the quality of indirect lighting, they do not directly increase the amount of light, but can increase the amount of light that bounces into dark areas.