Months ago I started to build a version 1 of a huge millionairs mansion in The Sims 3 that was for my laptop to big to handle. The watch it, click on this:
http://www.youtube.com/watch?v=168MU4IIq5EWhile making it I was constantly thinking of: how can I improve the house?
The question what makes the perfect house can be answered by a few simple guidlines I think:
1 Don't make the sims walk to far to get from point one to point two (like from the living room to the toilet).
2 Make sure that no matter who is going to live in the house, the whole interior will give the sim the possibility to fullfill his or her lifetime wish.
For the rest I hope some of you can upgrade this list with some things you came up yourself by for example experimenting ingame.
I have a lot of ideas to, but now I am more curious about your idea of what makes a sims 3 house perfect.
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EDIT:
Here are a few guidelines to make the most out of a room:
1 Every room needs the following things; 2 heartform gems like opal, pink diamond, rainbow, or soulpeache, 1 huge masterpiece painting, or 2 normal or 3 little ones (or your own combination of statues etc) to provide the sim that walkes the room with the +40 nicely decoration moodlet.
2 One most expansive stereo per room upgraded to better boxes or sounds (or whatevever the English term is), except for the bedrooms, unless your sims are heavy sleepers.
3 One most expensive fireplace per room.
4 One rubber ducky per bath in every bathroom + that head and shoulders thing that upgrades baths to bubblebaths.
5 One stove per kitchen upgraded to make better prepaired food, one food replicator per kitchen and also 1 5 star cheff fridge.
6 Per room 1 scented candle from the France, Egypt and Chinese destinations that came with World Adventures to provide the sim with a +10 mootlet each, and also with some better change of learning skills, romantic interactions and another thing that the egyptic scented candle does, which I've forgot.
7 Every object that can be upgraded in the rooms are upgraded to self cleaning and once repaired by a sim that makes the object never break again.
9 Every object that can scientifically upgraded will be upgraded. Especially those in the nurcery, because the moodlets that came with an scientifically upgrded object are also influencing the mood of a baby or toddler.
OPTIONAL: put teleportation platforms (upgraded to perfect teleportation and once repaired by a sim so it will never break again) somewhere in the corners of the house to make sims travels quickly. Your mansion will probably big, so you better decrease the traveltime.