Via Official Forums
What you’re missing here is that creating a world designed from the ground up to work with weather is much simpler than making weather work in every single world that we’ve already shipped.
When we design worlds for expansion packs that introduce new features, those features tend to play best in that world because it was designed with those features in mind. Someone said… oh, well pets worked in every single world, of course weather would as well. And sure, at the very base level that statement is true. But at the same time, we had a small team working on pet routing ever since the base game shipped, especially taking into account the horses. Appaloosa Plains was specifically designed to have larger open areas for the horses to run around in for natural game play with the horses. Can horses route around in other worlds? Sure… but it’s slower for them to get around and they have to make more adjustments in their routes to account for tighter spaces.
Now when you look at it from that perspective, you can apply that same line of thinking to weather, only amplify the impact it has exponentially. The weather effects have a tangible impact on the world and it’s something that every player will constantly see while playing the game. Weather spawns objects, FX, enables shaders, changes lighting, changes audio ambiance, changes roof and object geometry, and actually modifies terrain geometry (the most significant challenge by far), and more throughout the entire world. Now, if we built a world from the ground up knowing exactly how the weather system would work, and created the world in such a way that any known issues with how weather interacts with our worlds would simply be avoided by not building the world that way… well, that’s simple. But doing that and then enabling weather in every single other world would introduce a mountain of problems that would become readily apparent.
Beyond all the technical challenges I just went over, we also have to account for the performance impact that weather has on a player who is playing Seasons on our minimum recommended specs. Again – if we were creating one world that was specifically being crafted to enjoy weather in; we can build that world knowing exactly what impact it will have on performance when weather is enabled. By supporting every single world that we’ve already created, we have to ensure that when weather is turned on in-game that you can still play the game with reasonable performance in every world that we’ve crafted to date. That requires extensive planning to account for every situation we can think of, and then significant rework to adapt to issues that were impossible to anticipate due to the unique ways that various things were built in each of the worlds and how the process for building worlds evolved and was streamlined over time.
So like I’ve explained previously, we had a choice to make. As a producer, part of my discipline’s job description is to take the budget and man hours we have for each project and spend them in the way that creates the best game we possibly can. For Seasons, we could have spent that time crafting a custom world that would look beautiful with weather in it, or we could spend that time applying weather to every single world and addressing the issues that appear by turning on weather in worlds that were never originally designed to accommodate it. It would have been impossible to build our previous worlds knowing how weather would impact them, because until all those details were hammered out over the past year of development we had no way of knowing how weather would be implemented. When you get your hands on the expansion in a few short weeks, you’ll see that the experience we crafted in Seasons has nothing to do with things you may have seen in Ambitions, comments made about weather in Late Night, etc. We built the weather systems from the ground up in Seasons and it’s unlike anything you’ve seen in a Sims game before. I’m super proud of what the team accomplished and it is a big step forward for The Sims.
On a final note, I make every attempt to be straight forward and honest with the Sims community so that we can have an intelligent discourse between fans and devs. It’s my belief that approach makes for a better product where we can respond to fan requests or alternatively, help you understand why something wasn’t implemented a certain way. I greatly appreciate the feedback that we get; having such an active community is a great boon to what we do every day.