It is also worth noting that World of Warcraft Classic isn't exactly an archive from 2006. It has been rebuilt from patch 1.12, using modern data architecture and reaps the benefits of the modern engine. This means a lot of non-controversial quality-of-life features will still be present and it is possible to run WoW Classic servers on modern server architecture. As you can imagine, much has changed in the last 13 years in the tech space. That's before smartphones were even a thing. The modern engine no longer allows certain behaviours that could be used to get out of bounds, also adds widescreen monitor support and accessibility options! However, it does have the disadvantage of not being able to run on 32-bit systems which isn't that kind to older systems considering the game is from 2006.
This was a good start, but there were issues with how the developers used to handle updates to the database data. Unlike the source code, for which Blizzard had archives for multiple branches of the game that could be worked on and developed as separate pieces, early database data was overwritten with each commensurate update. Thankfully, that problem was fixed very quickly after launch, and when we looked, we found data going back to version 1.12—and even earlier.
For another example of lighting, we looked at Elwynn Forest. We had a period in Warcraft’s history where we changed all the lighting equations and as a result, our environment artists had to take a pass over all of the zones to improve the lighting and take advantage of the new equations. To recreate the original experience, we had to rewind those changes. The first thing we did was restore the old lighting data. This brought us much closer to the original lighting—and with a few more changes to the distance formula, fog formulas, and some changes to shadows, we were able to bring things even closer to the original lighting.