Since I started contributing to the C2C modding efforts (and more recently AND) I have become increasingly frustrated by incompatibility of save games from one version into a slightly changed version as the XML assets evolve. Basically this means I never get beyond the middle ages before new assets render my games uncontinuable.
As a result I decided to do something about it.
This post is a slight pre-announcement, but I'm very excited about this change, so hopefully you'll foregive me for that. I am currently in the final stages of testing, but I expect to be pushing the changes to SVN in the next day or two. After I do I'll make a detailed technical post giving the details of how it all works for modders reference, but for now here's a brief summary in the form of a FAQ list:
What do I mean by saying the changes will enable save-game compatibility between mod releases?
An option will be provided on save, to save in an extended format, which will be loadable even after fairly radical changes to the mod XML, or future DLL changes. In particular you should be able to expect to continue existing games in updated versions of a mod, unless the changes to the mod are of an extremely radical nature.
What are some examples of mod changes that will NOT prevent save games from loading with the new format?
Most changes frankly. For example, adding buildings, units, civics, techs, improvements, resource types and so will no longer break saves. Removing these things will also not break saves, though in cases where removed entity is in use in the save it will be removed on load if no longer valid (and you'll get a visible warning that this has occurred). Obviously if the mod changes relationships between already-extant (in the save game) entities (e.g. - changes requirements for building something) then the save game will potentially contain things that you would not be able to create in the same conditions after the mod update (so if a building got a new required tech say, you would still have the building if you had already built it previously).
What will still make a save game unloadable?
Pretty much just DLL changes that don't stick to certain rules (which I'll clarify in a technical post after this gets pushed)
So should I continue old games just because I can?
Up to you. If the load gives you warnings that some of the types it needed could not be found (which implies units/buildings/resources or whatever it warns you about have been removed) then you need to weigh the loss of fidelity against the benefits of not losing your investment in time in that game.
What are the downsides?
Using the new format will result in larger save files (about 40%) and slightly slower loading and saving.
When will the new format be used, and when will the old format be used?
Auto saves will continue to always use the old format because it's smaller and faster. This means you can't assume autosaves will be loadable in future releases (so same as now). Explicit save requests from the main save menu will now pop up an additional question asking you which format to use.
When do I recommend using the new format?
Depends who's asking ;-) This new format should be considered beta functionality, so for most end users I would say from day to day continue to use the old format. When a new mod release or patch becomes available make a save in the new format so that you'll be able to load it again after updating the mod. Modders on the other hand might want to save in the new format all the time since they are likely to be making XML changes frequently (and because they want to be helpful and give it some additional testing!)
I hope everyone enjoys the ability to continue games even on mods that change very frequently (looking at you C2C), and I trust you'll forgive my excitement with this.
As a result I decided to do something about it.
This post is a slight pre-announcement, but I'm very excited about this change, so hopefully you'll foregive me for that. I am currently in the final stages of testing, but I expect to be pushing the changes to SVN in the next day or two. After I do I'll make a detailed technical post giving the details of how it all works for modders reference, but for now here's a brief summary in the form of a FAQ list:
What do I mean by saying the changes will enable save-game compatibility between mod releases?
An option will be provided on save, to save in an extended format, which will be loadable even after fairly radical changes to the mod XML, or future DLL changes. In particular you should be able to expect to continue existing games in updated versions of a mod, unless the changes to the mod are of an extremely radical nature.
What are some examples of mod changes that will NOT prevent save games from loading with the new format?
Most changes frankly. For example, adding buildings, units, civics, techs, improvements, resource types and so will no longer break saves. Removing these things will also not break saves, though in cases where removed entity is in use in the save it will be removed on load if no longer valid (and you'll get a visible warning that this has occurred). Obviously if the mod changes relationships between already-extant (in the save game) entities (e.g. - changes requirements for building something) then the save game will potentially contain things that you would not be able to create in the same conditions after the mod update (so if a building got a new required tech say, you would still have the building if you had already built it previously).
What will still make a save game unloadable?
Pretty much just DLL changes that don't stick to certain rules (which I'll clarify in a technical post after this gets pushed)
So should I continue old games just because I can?
Up to you. If the load gives you warnings that some of the types it needed could not be found (which implies units/buildings/resources or whatever it warns you about have been removed) then you need to weigh the loss of fidelity against the benefits of not losing your investment in time in that game.
What are the downsides?
Using the new format will result in larger save files (about 40%) and slightly slower loading and saving.
When will the new format be used, and when will the old format be used?
Auto saves will continue to always use the old format because it's smaller and faster. This means you can't assume autosaves will be loadable in future releases (so same as now). Explicit save requests from the main save menu will now pop up an additional question asking you which format to use.
When do I recommend using the new format?
Depends who's asking ;-) This new format should be considered beta functionality, so for most end users I would say from day to day continue to use the old format. When a new mod release or patch becomes available make a save in the new format so that you'll be able to load it again after updating the mod. Modders on the other hand might want to save in the new format all the time since they are likely to be making XML changes frequently (and because they want to be helpful and give it some additional testing!)
I hope everyone enjoys the ability to continue games even on mods that change very frequently (looking at you C2C), and I trust you'll forgive my excitement with this.
