I was able to replicate TS4's indoor lighting in TS3, and it looks AMAZING!
I apparently can't post images in main body of the post anymore? So there's a tutorial below. :)
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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
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
