Virtous has handled a lot of Switch ports, including the high-profile releases of XCOM 2 Collection and BioShock: The Collection. In an interview with Automaton Media, Virtous' Zhang Chengwei talks about the biggest challenges the team faced with each game. You can see his answer below, courtesy of a translation via NintendoEverything.
Our biggest challenge with XCOM 2 Collection was memory optimization. The PC version uses over 7GB of memory, while the Nintendo Switch is limited to using only 3.2GB of memory. We had to continuously profile the game, make decisions, implement and test them, then profile again. We spent nearly six months optimizing just the memory. We tried many different methods using more efficient file formats, getting rid of unnecessary memory usage, and ultimately changing the original console’s memory system. The process was like wringing water out of a sponge: the more water we’d wring out, the more difficult and complex the process would become.
The challenges we face when porting a game are totally different from those on a typical development project. Firstly, we need to confirm whether or not we have all the original source code and data. With BioShock: The Collection, we recognized during the initial stages that some data had been lost, which took time to resolve. Secondly, the engines and middleware used in the original games are most often very old – especially middleware that was originally closed source. For example, BioShock and BioShock 2 use an extremely old version of Havok; it took us months just to contact and sort things out with the vendor. Lastly, players have very high expectations of a ported game’s quality. There’s almost always videos uploaded to YouTube comparing things like frame-rate, visual quality, load times, and so on. The way we ensure the quality of our games is also a huge challenge for us. Most often, it’s tied closely to the timeline and the cost of the project.
While there was a ton of work involved in each port, they didn't take a lot of time overall. Chengwei says that each project took roughly 10 months to complete.