You can find the link to Shotgunefx's Path Recorder here.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=180944985

For this guide you will also be needing Crowbar, a model compiling and decompiling tool. You can download it by visiting their group, at https://steamhost.cn/steamcommunity_com/groups/CrowbarTool.

If it wasn't obvious enough, you should already have Hammer installed, as this tutorial is for an intro camera for your map.

Once you have subscribed to the mod, launch L4D2. When it finishes downloading, open up the console. You can do this by pressing the ~ key, right above Tab. Type "map (yourmapname) v2cam". (yourmapname) can be any map you want. Once you selected your map, hit Enter and you should be loading in with the gamemode "vscript2smd IntroCam."
https://i.imgur.com/bzf11kK.png

If you cannot open the console, you must enable it in the Options. Go to Options, Keyboard/Mouse and locate Allow Developer Console and enable it. You should now be able to perform the steps above.

Now that you've loaded up the Path Recorder, you can finally start using it. Type in chat, "!help" to see all the possible commands you can use. A lot of it looks complicated but in reality you'll only be using around 7 commands.

Once you have finished creating your path, type "!name (customnamehere)" into chat and give it a unique name. Then type in "!save". Your intro camera's path has been saved.

Navigate to your left4dead2 folder. (Program Files (x86)/Steam/steamapps/common/Left 4 Dead 2/left4dead2) Look for the folder "ems." Open that up and open "vscriptcam." Locate your intro camera, it should be named what you gave it before you saved it inside the Path Recorder. Open it up and you should find 5 files.
https://i.imgur.com/o7DrnHX.png

"generated.nut" allows you to reload the camera later inside the path editor for further editing. It shouldn't be of any use to you.
The .qc file and the .smd file are what we are going to use to compile the camera path.
The .vmf will be used later.
The .vmx file is irrelevant for this guide. If you do not have this file, don't worry.

Copy and paste the .qc and the .smd into a folder on the Desktop. Name the folder anything. Open up Crowbar. Click the "Compile" tab. Replicate my settings here.
https://i.imgur.com/xgcVnfI.png

You may have to set up Crowbar before you are able to to compile anything.

Make sure QC input is set to Folder. Obviously the folder location doesn't have to be exactly that. It can be more organized if you want. Hit the "Compile" button. Your Intro Camera has been compiled.

Navigate to the output you chose. You should see a new folder called "models." Open that up, then open up "v2cam." You should see 3 files. All are important. Go back to the "v2cam" folder. Move it to your actual models folder for L4D2. You can do this by navigating to your left4dead2 folder and moving it into the "models" folder. You can now use the model in Hammer.

Now that you've compiled the camera model and put it inside your game files, you can now use it in Hammer.

First thing you want to do is navigate back to where you orginally saved your camera path. (left4dead2/ems/vscriptcam/(whateveryounamedit)) We are going to be using the .vmf file to get it as accurate as possible into your map. Load the .vmf into hammer. You should see a black void with your camera model. Place a "func_instance" exactly on the origin of the map. Once you've done that, select everything and copy it. Load the actual map you're working on in Hammer and Special Paste it into your map. Special Paste pastes it exactly in the same spot the original is. Press CTRL+SHIFT+V to use it. Hit OK and your camera model should be in the exact spot you recorded it and the func_instance should be exactly on the origin. Delete the func_instance as it has no use anymore. You are ready for the final step(s).

The final step in this guide is to get your intro camera to actually play in your map.

Follow this tutorial made by Roflmahwafflz.
-At 3:36 he creates a prop_dynamic entity which he uses as the camera. Completely ignore that step, as the prop_dynamic camera has already been pasted in with a name.
-Shortly after he chooses the model for the prop_dynamic he chooses an animation for the camera, ignore this as well. We're going to be using an animation titled "intro".
-At 4:46 Rofl selects all of the point_viewcontrols and parents them to "ghostanim." Parent yours to "pathmodel". Pathmodel is the prop_dynamic which is the animation for the camera.
-At 5:40 he creates an output inside the director entity which sets the animation of the prop_dynamic to the one he chose. Target the output to fire at pathmodel. Set the animation to "intro".
-At 6:11 he creates an output to trigger the next relay after a delay of 9.4 seconds. I'm pretty sure the delay is how long the intro animation is, so you should just set it to an arbitrary number and come back later once you've finished everything and make the delay the actual length of the intro. You can find out the length by timing it.
-At 8:53 he adds 4 outputs which sets the parent attachments of the survivor cameras to "Attachment_1." Instead of using "Attachment_1" we will be using "camera".

Now that you have completely done everything right, hopefully, you can now compile your map and your custom intro should be playing. Hopefully it was worth it.

Thank you to shotgunefx for creating this great mod and thank you to Roflmahwafflz for creating your video because without it I wouldn't even know how to create an intro camera.