Arthmoor wrote:With Skyrim Special Edition on the horizon, and with the go ahead given to be able to discuss modding technicalities finally given, it's time to throw up a quick list of things I've noted need to be done in order to get an existing mod from 32 bit Skyrim to work on Special Edition.
If your mod uses a BSA file (and pretty much any decent one ought to be if it has assets to provide), you can't simply use that file with SSE. The game will either hang or crash at the opening menu. Fortunately all you need to do in this case is unpack your existing BSA file somewhere and then use the new archive tool that comes with the new CK to repackage it. The reason for this is that they've changed the header structures and compression methods.
Animation files for 32 bit will not work out of the box. Depending on what they are, you may end up with NPCs or the player stuck in a default pose unable to move, or perhaps even being unable to move the camera at all. Fortunately Bethesda has supplied a tool with the new CK that will allow you to update your .hkx files to the new format. This is presumed necessary due to Havok being upgraded to 64 bits.
Water and Flow Data
There are numerous instances throughout the game that have been updated to take advantage of the new water flow mechanics that were introduced. So far as I can see, every river has had the flow type changed and new drop in icons have been placed to indicate the direction the water should go. In some cases the type of water has also been changed. Mods which edit cells with water in them will need to update this data or they're going to cause noticeable patches of rivers, lakes, and even the ocean that don't look right or flow properly with the surrounding cells. Yes, Bethesda themselves forgot to account for this in their DLCs too so guess who's going to have to fix that now
New Ground Clutter
If you've been watching any of the new footage that's all over Youtube you're either already aware of this or are wondering if it might be true. It is. There's TONS of new ground clutter objects all over the place. Mostly plants and shrubs, but some occasional rocks and other small things as well. Mods which edit populated areas will need to be mindful of this when updating so that the new plants can be accounted for. All of this was added to Update.esm so if you're not already using it as a master, you need to be, so that you can move these new objects out of the way of your stuff to avoid ugly clipping. It also appears some landscaping may have been done too.
Nothing new here, but I'm mentioning it because there are rumors afoot that they will break. They won't. Your scripts can be copied over as-is with no modification. Absolutely no changes to any of Skyrim's 13000+ scripts were made beyond many of the DLC ones getting recompiled with their debug statements commented out. Which the source code had already but the .pex files did not.
Meshes for SSE may need to be updated. There have been some changes which the Nifskope guys are better equipped to explain but the updated format for them lies somewhere between what 32 bit Skyrim offers and what Fallout 4 offers. So far as I've been able to tell, all of the ones my mods have work, and USLEEP's fixed ones aside from one troublesome Horker work too. There's some possibility that old meshes may be a slight performance drag but it may not be enough to matter in the end.
The only significant thing that's changed here is that SSE is no longer supporting .tga based textures. If your mods happen to be using those for some reason, they need to be switched over to using .dds textures instead.
ESP Files + NPC Facegen
ESP files need to be loaded into the new CK and saved out to be sure they're updated correctly. If your mod includes edits to NPCs or new NPCs entirely, you absolutely MUST do this. Failure to do so will result in your NPCs having heads which are entirely black - not just the usual issues with the familiar grey-face. The CK will automatically update any needed facegen data in your mod, and it may generate some for you that you didn't know you needed. When it does, don't include the .tga files it still generated because the game will ignore them entirely.