Tsuey Analysis: Dark Carnival 2 Trash Bin Team Shortcut

Most L4D2 shortcuts are mainstream nowadays. People can be fairly critical of Valve not "fixing their game" by patching them out despite their having become decade-old gameplay cornerstones -- so much that speedrunning communities use older, unpatched versions to revive original shortcut behavior. The vast majority of shortcuts result in one deserting their entire team, or singling out those incapable for ridicule if skill-based. This is a comprehensive analysis of the best shortcut in terms of both distance skipped and teamwork -- and one of which whenever I've performed in a Public VS game isn't even met with resentment, but rather most opponents just being paralyzed with shock and awe.

A bold introduction

DISCLAIMER: GIVEN THE PRECISION NECESSARY FOR THIS SHORTCUT IT CAN ONLY BE BEST EXPLAINED BY TECHNICAL APPROACH. IF YOU WANT TO SKIP THE TECHNICAL AND JUMP STRAIGHT TO DOING IT, JUMP TO THE EXECUTION WALKTHROUGH SECTION.

IF YOU'RE ONE FOR JUST DOING: SUBSCRIBE TO ᴿᴱᴻᴱ™'S BIN MAP TO JUMP RIGHT IN.



That's a pretty bold or naive claim, isn't it?

It's meant to be sensational -- because the point of this guide is to demonstrate how it's not so far-fetched at all.

Of the effectively infinite number of places you can throw pipe bombs, there's only 1 set of coordinates that reliably reproduces the placements above. I've tested it over several thousand lifetime attempts over about 6 years, and given its heavy reliance on RNG given pipe bomb and trashbin physics, only succeeds roughly 1/6 of the time with absolutely identical (setpos_exact) execution each time.

To be clear about the Dark Carnival 2 Fairgrounds area I'm talking about, take a look at this:



In terms of VS distance the shortcut illustrated on the left allows the entire team to skip 20% of the map, and arguably its best Infected attack at the ladder chokepoint -- and it's not even cheap, because if the Infected team is highly aware this actually adds a fatal one-way drop into the map to even balance things out:



The command r_drawclipbrushes 2 is used above to show the shortcut's exit point. After blowing up and climbing the trashbins, this is the hole you walk out of (you will not hang and there's no need to hold space to not hang) back into the map's critical path near the slide. I'd like to take this opportunity to say that the wall separating the fairgrounds from the slide is clipped to skybox (except for a prop_dynamic gate used for idle warping shortcuts not possible in VS mode), which is why you can't jump over it. This spot in particular, if you don't drop out of the hole into the slide area you will get permanently stuck in the area beneath the track (on the left side of the image).

Historical influences

L4D2 is no stranger to the manipulation of physics objects for an advantage:

1. Soft-blocking doorways on No Mercy with TV's to prolong attack exposure.
   
2. Using the Dead Center 2 shopping carts to expedite cola return.
   
3. Using the Dead Center 3 office chair to circumvent the one-way drop for Tanks.
   
4. Spawnblocking the Dark Carnival 2 safe room by clipping the trashbins through the door.
   
5. Disregarding the countless mapbreaking exploits involving forklifts, floodlights and generators.

But there's really one significant place it all started...

L4D1 had an awesome mainstream trick on Death Toll 2 Drains Survival where you'd pipe bomb launch the wooden crate up and camp out in the tunnels instead. Unlike the Dark Carnival 2 trashbins, this trick was extremely reliable to pull off and you could instantly restart ad infinitum until you got it right:



Unfortunately -- like the Last Stand Survival map -- this Survival template was never moved into L4D2... its only spiritual remnant is the fact that its sequel nailed down server-side physics objects until the timer is started precisely to deter this kind of classic exploitation.

L4D2 has been out 10 years and ripped apart in every conceivable fashion -- but, a gamebreaker's pique intrigue is always captivated by the allure of the unknown. Clipcrouching through walls is one such largely untapped exploit that has very niche scenarios of use I'll discuss in a very future guide... but for now, this guide aims to exhaustively cover my favorite and most practical trick in the game.

Speedrunners would scoff at this shortcut strategy given its randomness element and the existence of simply faster alternatives, such as tossing a bile jar up into the same area and common hopping up the Infected ladder instead (thereafter supplementing idle warping to re-unite the Survivors) -- negating the time needed for both aiming the pipe bomb and waiting for it to explode:



But we can't ignore that L4D2 is a team game, and the best shortcut is one which the entire team can execute together, regardless of skill level -- even if the initial setup requires a substantial chunk of luck.

This shortcut also reasonably requires TAS-like (Tool-Assisted Speedrun) precision through use of cl_showpos 1 to set up the throw -- it can be done without it, but in introducing a human element into something already requiring exact precision on top of heavy random elements, this shortcut is neither practical nor ideally legal in non-TAS speedruns.

L4D2 is largely an RNG game: it may come as a surprise, but that famous Dead Center 3 escalator death pull (amongst most others) fails even if the attacker and victim's coordinates are exactly identical with setpos_exact, over multiple testings, about 40% of the time resulting in a non-lethal hang:



Given how critical some attacks are in L4D2, and their demonstrable reliance on RNG, the 1/6 success rate of the trashbin shortcut isn't far detached.

The downside of quietly keeping a shortcut like this to myself is I have never seen it performed by someone else, and even instances of my own execution teammates are typically too unaware of how to follow through for it to be practical. Quite simply, I'd love to see it become commonplace as it doesn't even snub the Infected team as it actually gives them an opportunity for a real one-way drop attack, and it can effortlessly be countered by scratching the trashbins anyway.

Testing map

To jump in immediately and start testing this yourself, ᴿᴱᴻᴱ™ of HSTM Training renown has simplified it all here:

https://steamcommunity.com/sharedfiles/filedetails/?id=1720683949

The test map is highly recommended (as is HSTM Training) but if you'd prefer a more technical approach without downloads, see the next section.

Testing environment

This isn't the type of shortcut you watch some trendy HS Top video over then jump into a game right quick to start trolling -- no, it's incredibly delicate and will require your own testing environment with trial and error to not only observe that my coordinates actually do work extremely well, but also let you experience more than enough failure to discourage you enough to try and find better coordinates.

If you do find better coordinates or ones which also work, please post them in the comments or add me.

There's 3 commands that are intimately required for both testing and executing this shortcut:

] help setpos_exact
"setpos_exact"
 game cheat
 - Move player to an exact specified origin (must have sv_cheats).

] help cl_showpos
"cl_showpos" = "1" ( def. "0" )
 client
 - Draw current position at top of screen

] help sensitivity
"sensitivity" = "10.000000" ( def. "3" ) min. 0.000100 max. 10000000.000000
 client archive
 - Mouse sensitivity.

To start off, you'll need to open up a fresh instance of L4D2 and have console enabled, then input the one-time command string of:

sv_cheats 1; z_common_limit 0; sb_all_bot_game 1; sb_stop 1; map c2m2_fairgrounds coop

That will enable local built-in Source Engine cheats, nullify commons, allow all Survivor bot teams, cease Survivor AI, and load Dark Carnival map 2.

Once the map is loaded, then enter another one-time command string of:

sb_takecontrol ellis; kick nick; kick rochelle; kick coach; director_stop; cl_showpos 1

Note the cl_showpos 1 that is critical for shortcut execution, and further note that "cl_"-prefixed commands do not require cheats and can be used on any server. Otherwise, those commands make you Ellis, kick everyone else, and stop the Director.

Finally, there's 3 binds to make -- you'll want to change the i o p to something else:

bind i "ent_fire !self sethealth 0; host_timescale 10; wait 600; host_timescale 1"

bind o "setpos_exact -912.03 -1092.30 -69.928421;setang_exact 89 -90 0; give pipe_bomb; wait 50; slot3"

bind p "getpos_exact"

A description of each of those binds:

1. Bind i resets each attempt. You're lucky I regularly forget the working coordinates and have to re-find them again, optimizing this bind to be faster over time as my oldest efforts simply reloaded the map. Functionally, it sets your health to 0, and fast-forwards so you're instantly standing in the safe room again.
   
   
2. Bind o teleports you back to the trashbins with a pipe bomb equipped. It's a separate bind because you're going to want to change that setpos_exact often as you look for better coordinates -- but the one provided has about a 1/6 success rate.
   
   
3. Bind p is crucial for dumping your coordinates to console before every pipe bomb toss attempt. If an attempt actually succeeds, you'll definitely want record of where you were.

The flow of each attempt is thus:

1. Respawn in safe room (i)
   
2. Instantly teleport to trashbins (o)
   
3. Tweak your aim, always crouch, then dump coordinates (p)
   
4. Throw pipe bomb, jump off to observe trajectory
   
5. If failure, retry
   
6. If success, preserve console's setpos_exact coordinates and update bind o

Crouching is important just for limiting the distance the pipe bomb has to travel -- I have tested with and without, and crouching has always been proven better for me... but I challenge you to find coordinates where it's beneficial to stand!

To facilitate observation of the trashbin's trajectory, it's also useful to use host_timescale 0.1 which will play everything at 10% normal speed. Furthermore, the command boom (yes, simply boom) will spawn a live pipe bomb at your feet -- however, note that this isn't a realistic way to test since it's not subjected to the same thrown physics of a real pipe bomb and will inevitably land in unrealistic ways that cannot be reproduced in a live, non-sv_cheats game.

Analysis

This image largely speaks for itself:



But to throw in some numbers based on the Z (height) axis:

Z = 68 = standing on the point of the roof
Z = 125 = standing on the point of the roof and at the height of your jump
Z = 128 = standing inside the hole

Valve was extremely confident in this never being used as a shortcut given that it has always been unclipped and an env_player_blocker has never been added like for most shortcut fixes in _commentary.txt files, and given common pathing (nav_edit 1) there's simply far more consistent places to common hop than here. It has been historically reduced to a place for glitching Witches and Tanks and that's it.

All you need is the slightest height gain from a lowly trashbin to make the jump, and the provided getpos_exact coordinates put it exactly in the correct spot 1/6 of the time.

It's actually quite eerie how photo perfect it is nearly 20% of the time (and coincidentally skipping 20% of the map) -- it is outside of this guide's scope to cover the tremendous range of possible trajectories and results but I will say that:

1. Shooting the trashbin in midair to deflect momentum isn't enough force even with Autoshotgun.
   
2. Standing on the roof to block its trajectory or sliding off results in it simply going through you.
   
3. When it doesn't land high enough, shooting or bashing it will just make it fall more.
   
4. The pipe bomb's viewmodel fuse and sparks bobble to your character's movement but have zero influence on the pipe's final landing -- just to be absolute control about this, all 100 trials were conducted by waiting for all fuse movement to cease.

Furthermore, it's important to note the initial positioning of the trashbins:



The blue one was shot once with the pistol just to illustrate that their initial positions are "pinned" midair -- only once a force acts upon them do they actually fall.

This is important for a multitude of technical reasons:

1. Traditionally, physics objects which aren't "pinned" midair like this will "settle" once the map loads -- the problem is that those occurrences create RNG noise with regard to how it lands and settles. With these trashbins, given their floating state their coordinates are identical every single time.
   
2. The trashbins can be shot to "settle" them, but each time depending on where you shoot and RNG they'll land ever so slightly different enough to invalidate the functional toss coordinates.
   
3. The 2 left trashbins are absolutely critical -- the 2 right trashbins can be shot or "landed" impacting the trajectory minimally, but from my experiences the roof trashbin succeeds less often and the electrical box trashbin usually lands far away requiring several bashes wasting time.
   
4. Jumping on or off will not "land" them, and neither will any amount of movement on them. Only things like shooting or bashing will make them stop floating. This flexibility is critical for making this shortcut work.

To be clear: until proven otherwise, it's best to leave all trashbins floating.

I'm unfamiliar with how Source Engine gravity relates to real life -9.8 m/s^2 gravity, but if one were to analyze things that extensively we're talking about a dissertation-tier shortcut.

Trashbin physics object info:

] ent_dump !picker
inertiascale: 1.00
physdamagescale: 0.10
classname: prop_physics
hammerid: 1808054
max_health: 1
addon: ai_addon_thrownprojectile
friction: 1.00
glowbackfacemult: 1.00
spawnflags: 256
fademindist: 1000.00
fademaxdist: 1200.00
fadescale: 1.00

PROBABILITY

Using the coordinates found within bind:

bind o "setpos_exact -912.03 -1092.30 -69.928421;setang_exact 89 -90 0; give pipe_bomb; wait 50; slot3"

That spot was teleported to and the pipe bomb tossed without risking accidental mouse movement using:

bind z "+attack; -attack"

With the following denotations for outcomes:

O = success (both trashbins landed exactly as desired -- photo perfection)
Q = success (only the electrical box trashbin needed bashing)
X = catastrophic failure (subjective physics WTF)
A = roof trashbin landed but wasn't high enough (close-yet-so-far irredeemable failure)
B = roof trashbin landed but slowly slid off

Following is a series of 100 trials used as a sample size for assessing probability:

O X A B X X B Q A B X X O A X X X O O O
O X X X O B X Q X B B B B B B X X X B O
B A B B B B A A X X B B X A B X O X B B
X B O B B B B X X X B B B B B B O B B O
X X B X X A A O X Q Q B A B O B B X B Q

Thus, roughly every 1 in 5 attempts will succeed, but let's say 1/6 given that manual human coordinates can only at best match Y = -1092.30 given the decimal point limitations of cl_showpos 1.

If you've read my other guide on spec_goto it's also noteworthy that spec_pos cannot offer anymore precision than cl_showpos 1 already does:

] spec_pos
spec_goto -912.0 -1092.3 -7.9 89.0 -90.0
] getpos
setpos -912.030029 -1092.300049 -7.939171;setang 88.994751 -90.000000 0.000000
] getpos_exact 
setpos_exact -912.030029 -1092.300049 -69.928421;setang_exact 88.994751 -90.000000 0.000000

Carefully observe that Z is reported differently depending on the command used, but absolutely 100% does not matter since you're always going to be standing on top of the trashbin thereby making this Z automatic -- as well as the X, since you'll be flush up against the wall.

EXECUTION WALKTHROUGH

STEP #1

Type into console:

cl_showpos 1

And optionally bind something like this as an in-game reminder:

bind p "say_team -912.03  -1092.30  -7.94      89  -90  0"

STEP #2

Replicate these values and crosshair aim:



Note that you're going to be standing flush up against the wall and atop the trashbin respectively making your X and Z coordinates match the required automatically. The only coordinate you really have to worry about is Y = -1092.30 and being at a near-perfect right-angle.

Adjusting your sensitivity CVAR can help with fine-tuning adjustment.

STEP #3

Crouch (required), throw pipe, and walk off to watch the show:



Note the convenience of the roof it bounces off of -- if that wasn't there, this wouldn't be possible!

STEP #4

Climb the trashbins and once inside fall through the hole leading to the slide:



Don't fall anywhere else as you will get permanently stuck. Consequently, the risk of skipping 20% of the map is that this adds a Death Charge and Death Pull opportunity to a map that previously had few.

Any movement of the trashbins whatsoever by teammates, common, or Infected will result in profound failure.

Closing thoughts

An ulterior motive of this guide is my attempt to persuade others to set up similar test scenarios to discover other, similar high-precision tricks in the game. I've always taken this particular shortcut pretty seriously as -- unlike most -- it's one where you don't abandon your entire team, and doesn't fall to the mapbreaking cliches of common hopping, grenade launching, or VS-excluded idle warping.

Unrelated: I'd also casually ask to take a look at my guide Valve removed from the Hub, but it no longer contains any actionable exploits as Valve fixed it as a result of its spread but can still be exploited in other ways I'm not going to publish. In short, Valve should've cheatflagged spec_goto but rather decided to just break it more instead:

https://steamcommunity.com/sharedfiles/filedetails/?id=652991759

Special recent thanks to physics student Bozo The Clown for spending 3 hours offering a different perspective to testing unique coordinates I for years didn't think of trying and even instinctively thought to be absurd but were just clever -- unfortunately, it's narrowly apparent that there's still actually only one working coordinate solution.

I'd also like to thank HUMAN BEAN for encouragement and testing ~5 insane years ago to get this first working.

Hopefully this guide will encourage you to test it out yourself, and maybe find better coordinates!

At the very least, I'll now someday become a victim to this very thing in some Public VS game!

[NF]

Legendary guide

[TOILET SNIPER]

pain

[Tsuey]

It has been fun, but within 12 hours this shortcut will have been laid to rest by my own hands. This shortcut fell within the definition of "going out of bounds".

Follow more Last Stand Community Update bug/exploit fixes at:

https://steamcommunity.com/id/Tsuey/myworkshopfiles/

[Tsuey]

Just dropping a thanks! to everyone who has looked into this shortcut. Maybe we'll never find better coordinates, but we're more likely to never see a L4D2 content update from Valve -- my hope was that maybe a new "not really a shortcut" (since you're risking a devastating death charge/smoke to balance it out) would make it feel as if it was an update.

[TOILET SNIPER]

that's amazing!

[Majistic]

Wonderful guide with thorough analysis!

[Hyron]

This is a pain in the ass to learn, stop being so lazy and use the normal routes for god sake

[Air]

Epic! And nice write up.

[Tsuey]

Dear diary: HS Top commented on the guide on this day. It was indeed a day.

[Bozo The Clown]

epic guide