# How does burning work?

**URL:** <https://discourse.cataclysmdda.org/t/how-does-burning-work/3428>\
**Category:** The Bunker\
**Created:** [October 9, 2013, 7:34am UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428 "2013-10-09T07:34:47Z")\
**Posts on this page:** 15\
**Page:** 1

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**Author:** ![Miloch](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/miloch/32/1339_2.png) [@Miloch](https://discourse.cataclysmdda.org/u/Miloch)\
**Post date:** [October 9, 2013, 7:34am UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/1 "2013-10-09T07:34:47Z")

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When camping IRL you start with small stuff and build up your fire. Once you get that going you start adding bigger stuff and eventually logs. Logs you put on for extended camping. But when I have just logs in my stone fireplace they tend to go out eventually. Suggestions?  
Ok. I think I just answered my own question. Apparently logs do not act as a fuel. They get burnt but do not seem to be expended.  
This is very much so not the way it should be. Logs should be what one uses to build a long burning fire when one doesn’t have many matches. 😛

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**Author:** ![John\_Candlebury](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/john_candlebury/32/6437_2.png) [@John\_Candlebury](https://discourse.cataclysmdda.org/u/John_Candlebury)\
**Post date:** [October 9, 2013, 10:05am UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/2 "2013-10-09T10:05:56Z")

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A realist fire generation has been a longstanding problem with the game, what we have is definitively much better than a few versions ago but is still faulty in some aspects like what you described.

And as far as I know reworking fire is planned but on hold

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**Author:** ![Shoes](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@Shoes](https://discourse.cataclysmdda.org/u/Shoes)\
**Post date:** [October 9, 2013, 1:03pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/3 "2013-10-09T13:03:02Z")

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John, has someone made a roadmap or an outline of how fire should work? Fire and bodytemp go hand in hand.

Also, in your signature, you typo’d illustrated.

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**Author:** ![John\_Candlebury](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/john_candlebury/32/6437_2.png) [@John\_Candlebury](https://discourse.cataclysmdda.org/u/John_Candlebury)\
**Post date:** [October 9, 2013, 1:05pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/4 "2013-10-09T13:05:51Z")

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No Idea I only know that one of the main developers, perhaps Kevin? (I think) said he still wanted to improved

Sorry that I cant be of much help also thanks for pointing that out

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**Author:** ![Luissen](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/luissen/32/1025_2.png) [@Luissen](https://discourse.cataclysmdda.org/u/Luissen)\
**Post date:** [October 9, 2013, 2:22pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/5 "2013-10-09T14:22:45Z")

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I thought it was funny how I can ignite a house from the outside in the rain, but I see it as a feature 🙂

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**Author:** ![Endovior](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/endovior/32/3070_2.png) [@Endovior](https://discourse.cataclysmdda.org/u/Endovior)\
**Post date:** [October 9, 2013, 4:50pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/6 "2013-10-09T16:50:34Z")

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Burning logs has always been a little difficult; if you tried to burn them outside, they wouldn’t ignite until the ‘raging fire’ level, at which point they’d really get going, quickly resulting in a pretty humongous multi-tile fireball (careful where you light that!). I know that I’ve been able to burn logs in a furnace before, but it’s been quite awhile… version 0.6 IIRC, though it may have been earlier. Back then, you could get a raging fire going in a furnace, but it wouldn’t spread past that, meaning everything within could be properly burnt up. Unfortunately, more recent furnaces have restricted the fire strength, so that no matter how much fuel you put in, the fire never burns above the ‘small fire’ level.

You can still light more powerful fires outside, and a raging fire will eventually consume a log… but the awesome fireballs of the past are sadly gone.

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**Author:** ![Shoes](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@Shoes](https://discourse.cataclysmdda.org/u/Shoes)\
**Post date:** [October 9, 2013, 5:59pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/7 "2013-10-09T17:59:02Z")

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It would be interesting to tie fire size to its temperature (ignoring chemical fires), and having fuel increase temperature which would “increase its size”.

… I have an idea

Calculate a “fuel” number for each item, given their weight, volume, material. The amount of fuel in a fire would determine its temperature. However, fuel will only burn at a certain temperature. Paper wrapper might be “one fuel”, and can burn all the time. A 2x4 might be “ten fuel”, which would require a fire to have at least “ten divided by 2” fuel presently burning before it can ignite.

Given enough paper wrapper, you could burn a 2x4. But a 2x4 alone won’t burn.

I am thinking out loud, so I don’t know how feasible this is. Especially with things like molotovs and flamethrowers…

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**Author:** ![kevin.granade](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/kevin.granade/32/1316_2.png) [@kevin.granade](https://discourse.cataclysmdda.org/u/kevin.granade)\
**Post date:** [October 9, 2013, 7:19pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/8 "2013-10-09T19:19:03Z")

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Regarding how it works, here’s a rough explanation.

Spoilered to preserve sanity

Fields have an age stat, which is _intended_ to be set to the birthday of the field, and then checked against a field half life for dispersal of the field.  
Well fire eats that and craps it back out again, because a fire field freely manipulates its own age and then uses the (frequently negative?!?) age to decide what its intensity, spread, smoke production, etc should be.  
If a fire’s age goes positive, it’s “dying”, in other words it’s out of fuel.  
If it’s highly negative, it increases its own density (turns itself into a bigger fire).  
If it’s dense AND the age is still very negative, it starts spending down age by producing adjacent fire fields and emitting smoke.  
Fire reduces its age by consuming items, which is its own little brand of hell.  
The density of a fire field determines how many items it can burn at once, a small fire will only burn the first two flammable items in its square. (first? measured how? I don’t know.), With two more items being burned per density level.  
How fire interacts with an item is roughly dependent on item material, volume, damage, and “burn” (yep, items have a special stat just for fire interaction)  
Different materials contribute more or less age to a fire when burned, and are consumed at different rates.  
The product of volume and material, minus “burn” determines a threshold for how large the fire has to be to burn the item, logs just get charred because this threshold is too high, but the threshold is ignored for raging fires, yep, ignored.  
If a fire _can’t_ surpass this threshold, it instead adds “burn” to the item, to represent heating it up/smoldering, this brings the threshold down, but still not enough to e.g. burn logs.  
If a fire CAN surpass this threshold, it damages the item and increases its own age as it consumes it, how much age it gets depends on the material.  
Another output of consuming items is smoke, different item types produce differnt amounts of smoke, but in general fire puts out so much smoke that this is pointless.  
The burn rate/age reduction for wood is hand tweaked to make a pile of heavy sticks stay small pretty much indefinitely (well, as long as the wood lasts) to make crafting easier.  
This neglects the details of the really hairy parts of the code, like spread, density increases, and smoke production.

tl;dr I, and pretty much every other dev that’s looked at this code, want to nuke it from orbit and start over, but no one has stepped up to do so yet. The problem is it’s a nasty combination of essential for survival, dangerous, thematic, complicated, and performance sensitive. Oh, and the existing code kinda sorta works. The only really GOOD news is that there’s just one (big :P) chunk of code that needs to be replaced.

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**Author:** ![EkarusRyndren](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/ekarusryndren/32/80_2.png) [@EkarusRyndren](https://discourse.cataclysmdda.org/u/EkarusRyndren)\
**Post date:** [October 9, 2013, 7:45pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/9 "2013-10-09T19:45:56Z")

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My only complaint that I have with the fire system as is, is that currently if you accidentally start a fire indoors with anything bigger than a “small fire” and then suddenly the whole damn building is a raging inferno that is looking for your life.

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**Author:** ![jcannon98188](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@jcannon98188](https://discourse.cataclysmdda.org/u/jcannon98188)\
**Post date:** [October 9, 2013, 8:19pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/10 "2013-10-09T20:19:26Z")

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> [@EkarusRyndren](#):
>
> My only complaint that I have with the fire system as is, is that currently if you accidentally start a fire indoors with anything bigger than a “small fire” and then suddenly the whole damn building is a raging inferno that is looking for your life.

Almost like real life!

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**Author:** ![Chiko](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/chiko/32/3238_2.png) [@Chiko](https://discourse.cataclysmdda.org/u/Chiko)\
**Post date:** [October 9, 2013, 9:20pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/11 "2013-10-09T21:20:25Z")

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I had the genius idea of cooking my food indoors coz it was raining outside. I’ll spare you the rest. 😛

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**Author:** ![i2amroy](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/i2amroy/32/909_2.png) [@i2amroy](https://discourse.cataclysmdda.org/u/i2amroy)\
**Post date:** [October 9, 2013, 9:26pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/12 "2013-10-09T21:26:46Z")

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> [@EkarusRyndren](#):
>
> My only complaint that I have with the fire system as is, is that currently if you accidentally start a fire indoors with anything bigger than a “small fire” and then suddenly the whole damn building is a raging inferno that is looking for your life.

Yeah this isn’t that far off from real life. (In real life once a fire gets a bit too large then the smoke itself put out by the fire begins to cause things to combust, rooms can literally go from “that couch is on fire” to “raging inferno” in the space of a few dozen seconds).

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**Author:** ![esran](https://avatars.discourse-cdn.com/v4/letter/e/958977/32.png) [@esran](https://discourse.cataclysmdda.org/u/esran)\
**Post date:** [October 10, 2013, 1:57am UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/13 "2013-10-10T01:57:31Z")

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my probably is that a military bunker got set on fire, and the stone got set on fire and reduced to rubble.

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**Author:** ![Miloch](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/miloch/32/1339_2.png) [@Miloch](https://discourse.cataclysmdda.org/u/Miloch)\
**Post date:** [October 10, 2013, 3:49am UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/14 "2013-10-10T03:49:46Z")

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The game doesn’t differentiate between building tile materials much as of yet, at least not in my experience. A building will burn whether it would be made of stone or wood. Made the mistake of using a moltov when backed into a subway… Didn’t end well.

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**Author:** ![kevin.granade](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.cataclysmdda.org/kevin.granade/32/1316_2.png) [@kevin.granade](https://discourse.cataclysmdda.org/u/kevin.granade)\
**Post date:** [October 10, 2013, 4:24pm UTC](https://discourse.cataclysmdda.org/t/how-does-burning-work/3428/15 "2013-10-10T16:24:01Z")

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ok that’s a really good point, need an override for totally non-flammable terrain and furniture. Currently it can burn solid rock, but leave nails untouched 0\_o