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During the development, there's a few things we had to accept and among these is the fact that not everything is possible in a Left 4 Dead 2 campaign. Because of this, there's a few problems we are aware of but can't fix or didn't had the time to fix before release. Here's a little list just so you guys know what's going on.
BEWARE, THIS LIST CONTAINS SPOILERS REVEALING PART OF WHAT HAPPENS DURING THE I HATE MOUNTAINS 2 CAMPAIGN. YOU SHOULD NOT READ IT IF YOU DON'T WANT MOST OF THE ACTION SPOILED.
See the original post for a list of common things we can't fix:
LEFT 4 DEAD 2 ISSUES
THE SOUND SYSTEM NIGHTMARE-ISH
The Left 4 Dead sound system is rubbish and even if Valve is aware of this problem since over a year, they don't seem to plan on fixing it so custom campaigns have to suffer from incomprehensible issues that can't be fixed. Hopefully, the situation has improved with Left 4 Dead 2, but this is still not perfect since we're still missing some legacy support for some Left 4 Dead 1 sounds.
THE REAL PARTICLE SYSTEM NIGHTMARE
Unlike Team Fortress 2 (for example), Left 4 Dead 2 is not able to read custom particle systems embedded in custom campaigns. To make it work in Left 4 Dead 1, we had to overwrite all the particles of the original game and add our own particles. But since the DLC 'The Passing', this is not possible anymore. So far there's no way to embed custom particles anymore, and it's quite a shame.
NO MAP NAMES DURING LOADING
There is a possibility that no map name will be displayed on the loading screens between the levels. This is not something we were able to fix and we don't know where the problem comes from. IF you know about it, please tell us, but this is unlikely to be fixed some day.
At some points in the campaign, the spitter might encounter some precise spots where her spits will explode in mid-air next to rocks. This is because Valve's collision models for these rocks are clumsy as hell.
at least the sound system has been improved in both l4d1 and 2. About the mapnames, i tried with "displaytitle" in the mission txt file but that fails . WHat does work is that extra loading poster tile you need to configure in the vgui/maps folder to display the poster tile in ingame server listings.