I was able to replicate TS4's indoor lighting in TS3, and it looks AMAZING!

So I've always been jealous of how indoor lighting is in TS4, like how the light comes in through the windows like so...


Well, I managed to stumble across a way to replicate that in TS3.
So, you'll need to have decorative windows, they have to be decorative because you'll have to remove the part of the wall where the window will go.
You can get two ceiling length decor windows here -> https://marcussims91.tumblr.com/post/36849444925/pulltab-living-set-dining-chairs-eames-lcw-chair
If you know of any other decor windows please let me know because I'd love to be able to do this in other homes. But 8 foot windows sometimes don't make sense in some homes, lol.

Anyway, doing this will change the lighting of the room because the game won't realize that the room is closed once you put the decor windows in. So before you do anything the indoor lighting will look similar to this.
https://imgur.com/wczgwa2.png

Then remove the walls where the windows will go, and find the windows.
It took me forever to find them, so this is the name and what they look like in Buy Mode.
https://imgur.com/GQikZKy.png

And then start putting them in the empty wall slots. I had moveobjects on before I did this, you may be able to do this without the cheat though.
https://imgur.com/Lh2A2XA.png

The only bad part about these windows is that they leave a gap between the top of them and the ceiling...
https://imgur.com/DgM5vz6.png

But the creator of these included a wall block that you can place on top of the windows to block the space.
https://imgur.com/ipsf2cI.png

So then you can CASt it, but it may glitch like this. But in other parts of the warehouse it didn't glitch like this, so I don't know about that.
https://imgur.com/hFFscAc.png

And Voila! Now the light goes realistically through the 'window'.
https://imgur.com/ic8ZOGF.png

Even though it changes the indoor lighting a little (or it may not depending on what lighting mod you have) I think it looks amazing and adds a touch more realism.
https://imgur.com/0PEWyZR.png
https://imgur.com/i4EytpH.png

My sims cat, Mozarella seems to feel indifferent towards it, lol.
https://imgur.com/NqnDYwe.png

The shadows from the windows was removed from Sims 3 when they needed to make the greenhouse weatherproof. It was shadows with rain and snow falling inside the greenhouse or dry inside the greenhouse with no shadows. People really wanted their greenhouse roofs to be weatherproof.

Update: I have found more glass/window replicas that may fix the issue of sims thinking the room is open to the outside.

Glass Wall from here -> https://www.thesimsresource.com/downloads/details/category/sims3-objects-buildmode-fencesgates/title/glass-walls-01/id/1085966/
Glass Fences from here -> https://www.thesimsresource.com/downloads/details/category/sims3-objects-buildmode-fencesgates/title/big-glass-fence/id/1015674/
This is the glass wall, I would assume it encloses a room just like how a regular wall does, haven't tested it extensively yet.
https://imgur.com/PEfdS4Y.png

Stackable Glass Tiles from here -> https://www.thesimsresource.com/downloads/details/category/sims3-sets-objects-decorative/title/glass-tiles/id/1010822/
https://imgur.com/rB6Sw8w.png
https://imgur.com/W2Y0Vt7.png

Window Half-Walls from here -> https://gardenbreeze.tumblr.com/post/49772614386
https://imgur.com/b0rMtto.png
https://imgur.com/4tZVRY6.png

"Karritz;c-18065464" wrote:
The shadows from the windows was removed from Sims 3 when they needed to make the greenhouse weatherproof. It was shadows with rain and snow falling inside the greenhouse or dry inside the greenhouse with no shadows. People really wanted their greenhouse roofs to be weatherproof.

Wow, so shadows looked like that prior to whatever update that was? Interesting.
I haven't tested this yet during Fall or Winter, but since the room is technically 'open' my sim was getting the 'scorched' moodlet. I'll probably continue to fiddle with it and see if I can find other kinds of decor windows or maybe even half walls.

That's odd, I'm able to post images in my main posts but anyways, since it doesn't recognize the wall is finished, wouldn't that give the "unfinished room" moodlet?

@GraceyManor if you use the windows then yes, if you use the half walls or glass wall I would assume not. Then again, I haven’t tested it extensively yet.