Serious Engine 3.5 is the latest version of the Serious Engine. As it's name tells, it is based very closely on Serious Engine 3, but with enough drastic changes that it can be considered a mid-way point between Serious Engine 3 and a potential Serious Engine 4. it is only used in Serious Sam 3: BFE.
As with Serious Engine 3, Serious Engine 3.5 cannot be licensed for use by other developers.
Serious Engine 3.5 uses Serious Engine 3, just like it's predecessor. There are very few changes between the version of Serious Editor 3 used in Serious Engine 3 and Serious Engine 3.5
Here are the improvements 3.5 made on Serious Engine 3:
- Support for creating complex in-game cutscenes.
- Lipsynch support for speech during cutscenes.
- Animations have been separated from a model's files and now lie in their own file format in a model's folders.
- Better dynamic shadow support for things like palm trees being moved by wind.
- Netcode has been improved again.
- Vehicle support (itself a leftover from Serious Engine 2) is broken in Serious Engine 3.5, but works in Serious Engine 3.