nraas

As I'm a storyteller, I like to go into movie mode (tab) and scroll around in my sims' home and yard taking pictures - as if looking through their eyes. However, I wouldn't call my pictures that successful when taken indoors, because the roof partially or completely vanishes. They have a normal roof but when I'm in the house and look through tab view, I can see the sky, as if they suddenly didn't have a roof. Or there may only be a few visible ceiling tiles here and there...

Why is this and how can I fix it?

Put the ceiling under the roof and live happily. This is done as if you were laying the floor. And you can catch the desired angle in buy\build mode and paint the resulting boring ceiling with any textures.

Apparently this doesn't work if I have two level house without a floor in between. Is there a way to fix this?

Yes, you are right, the ceiling is needed for each floor, otherwise you will see the sky above your head. This trouble sometimes upsets me too. But I, for example, to create higher walls change the height of the level, using the cheat constrainfloorelevation.

Bummer.
Can I change the height of the level afterwards? For example, I have a horse stable in which I wish to have higher walls and ceiling far above (safer for the horses to rear and not to smack their head against the ceiling ).

Also another question, since I spotted you, Sara_Darkees, comment this on another thread. How can I set a door stay constantly open? You mentioned DebugEnabler, but can I do this with MasterController?

I've changed the height of the floor even with objects on it, but you'll have to put objects back in place if they falls or hangs in the air. Click on the object, and then click escape. Main thing, don't overdo it with height. The problem is that the height of the windows will not be able to raise. It's a pity we can't do it like in TS4, but maybe somebody ingenious will invent a mod for this. Here is an example how work this cheat. While you are doing such distortions, banish the characters from the lot and don't forget to then turn off the cheat, so that no one began to get stuck.
And with the MC door can't be opened, you will need DE. It's a really reliable method. Unfortunately, I don't remember exactly how this option is called, but I found it, so you will surely find it, too.