Writing BSP corrupts game lump

[Mooshua]

Issue When saving a BSP that contains static props and launching it with CS:GO, static props present in the original BSP no longer render. Occurs even when LibBSP performs no mutation

Reproduction

• Open a file with static props using BSPReader
• Save that file using a BSPWriter
• Attempt to open the file with CS:GO

Possible cause The valve developer wiki contains this note:

Note that fileofs is relative to the beginning of the BSP file, not to the game lump offset.

This value does not appear to be patched to the new location of the static prop lump.

[wfowler1]

D'oh, it figures I'd miss something stupid like this. It's hard to test every single thing for so many different games. I made sure to account for the offset thing in GameLump.cs on line 307, it's possible it's not working correctly. But I think it's more likely that static props are being written in the wrong format. I'm a little surprised the game wouldn't outright crash if that were the case, though. I'll have to do some comparisons.

These static prop lumps are such a pain.

[Mooshua]

I think your fix would work if lumps were serialized in the same order as they were serialized in the BSP, but if the lumpinfo becomes inaccurate then that means this will too.

I am also surprised it isn't crashing the game

But I think it's more likely that static props are being written in the wrong format.

I disagree. I used VIDE to extract the lumps and the only difference between a working game lump and a bad one is the offset in each gamelump's header.

[Mooshua]

Hi--I got this working on a local fork. It's super messy and I'm not sure you will like it, but it should give starting point:

Approximate changes:

• Add BSPHeader as an argument to GetLumpsBytes
• If statement in GetLumpsBytes to see if lump is 35
• If so, pass additional argument lumpBytes.Sum(o => o?.Length ?? 0) + header.Data.Length to the GetBytes method
• Add lumpWriteOffset parameter to GameLump.GetBytes (+ add dummy method to fill interface)
• GameLump.GetBytes: New offset calculation: int offset = lumpDictionaryOffset + (lumpBytes.Count * lumpInfoLength) + lumpWriteOffset;
• Comment out into.offset += LumpInfo.offset in GameLump.GetBytes
• GameLump.GetBytes: lumpBytes[pair.Key].CopyTo(bytes); -> lumpBytes[pair.Key].CopyTo(bytes, offset - lumpWriteOffset);

This probably could have been fixed better by simply modifying the LumpInfo field for each lump to match the new lump location during the write.

Hope this helps. Good luck!

[wfowler1]

Interesting. I haven't had the chance to look at it yet, hopefully I can dig deeper soon.

[wfowler1]

Ok I've got my solution in place, it's probably similar to what you've got. Let me know how this goes.