Evaporation

[guilden]

was trying to figure out evaporation after reading virgilw's response on:
http://knucklecracker.com/forums/index.php?topic=33.0



enclosed pools cut off from source never evaporate,

pools with exposed sides won't necessarily evaporate either,

initial creep pool. no evaporation. pushing to take new ground despite lack of source.


no evaporation, regenerates up to that point when lightly bombed at the entrance. yay drones.


pushed a little harder, shrinking the size of the pool but exposed area staying the same, finally trigger evaporation.


seems you need to have enough exposed surface area on the creep pool in order to trigger evaporation.
and the threshold of necessary exposed surface area on the creep might be related to the size of the pool.

trying to figure out how to more efficiently force creep into evaporation so I can do other things with my energy, you guys figure anything else out?

[knucracker]

Yes.... good old evaporation.  Started out as a minor goof up while developing the game and turned into a key for making the creeper work in the most "fun" way.   What follows is a rather lengthy explanation, so be warned.

So most people think of the creeper as a thick syrup that is poured onto the map.  The little emitters erupt at regular intervals and spew some amount of Creeper onto the map at each eruption.  For most all purposes this is a perfectly good way to think of the Creeper....

But guess what.... that isn't how it is modeled at all.  The Creeper is actually modeled as heat flow through a conductive surface.  At least that is mostly how it is modeled.  A thermodynamic expansion model certainly controls how it spreads.  So heat once introduced into a system will spread/conduct through the surface and it will also radiate away.  But it isn't radiation that causes the Creeper to go away.  You have noticed this by noting that a closed pool of Creeper will never go away.

Even thought I model the expansion of the Creeper as heat flow, there is no general purpose radiation that causes heat loss in Creeper World.  So heat/creeper once introduced will spread through the medium(the terrain) and eventually spread completely evenly (ignoring terrain height which is another story).

Weapons in Creeper World are heat "Destroyers".  There is no such thing really, but you can think of a bomb like someone touching a really cold heat sink to the surface for a split second.  Heat from the map will conduct into the heat sink and leave the map.

If the story stopped here, you would still be left wondering what causes evaporation... and you'd be right.  It is caused by another rule I put into the game that has nothing to do with heat flow.  Basically, once the heat drops below a certain level it gets clipped to 0.  Even though it should just asymptotically approach zero, once it drops below 0.001 the heat value at a cell on the map gets set to 0.  So the heat disappears once it goes below a small enough value.  I'm not sure there is an analogy to this in the physical world....

So back to thinking of the Creeper as evaporation; You could think of this as evaporation, but it only happens at map cells where the creeper is really thin.  On map cells where the Creeper is above 0.001, evaporation is zero.  On map cells where the Creeper is 0.001 or less evaporation is 100%.

When you have an isolated pool of Creeper (no resupply) that pool will start to spread out. As it spreads, each cell gets thinner and thinner.  The leading edge cells are really thin eventually.  Depending on how much creeper is in the pool the pool can spread to occupy the whole map or it may only spread so far.  If there isn't enough Creeper to keep the leading edge at 0.001 or greater the cells of the leading edge will lose their Creeper completely.  This moves the leading edge back a little bit and the process repeats.

You can see this effect clearly in a map where there is a pretty weak emitter.  The creeper will flow away from the emitter but only so far.  The southern emitter in the second story mission is this way.  Start that mission and don't do anything.  Just let the Creeper from the bottom emitter spread... it will only spread so far because the leading edge is so thin that Creeper will be continually lost.  The 'bubble' of Creeper will expand till the exposed leading edge produces a loss that equals the Creeper being injected by the emitter.

You can also experiment with this using the map editor.  Just create a flat map and put an emitter in the middle of it.  Make the emitter stronger or weaker and notice how big the Creeper expansion bubble is.  Make it powerful enough and no map will hold it all.  The Creeper will flood everything with no hope of evaporation.

(If you want to join in on the Beta fun so you can play with the map editor, just let me know and I'll add your account to the beta group so you can get access to the map editor).

[guilden]

woot, I'd very much like to be a beta tester

[knucracker]

You're in.  You should see a new group called "beta" now.  In there you'll find the links for the map editor, etc.  There are already some new maps posted there as well.  Feel free to get creative (or destructive) and add any map you may come up with to the collection.

[dePoPo]

Great explaination on how the creeper works :) very cool concept.

The outlook of a map editor will make this game re-playable for ever - great work !

[knucracker]

So the map editor is pretty much done.... I hope to have it posted on the site tomorrow.  I'll also be hosting maps on the site so if anybody makes any maps they want to share, everyone will be able to enjoy.

[Aurzel]

(is this old enough to be considered a thread res? lol)

in relation to the op, i did read the others and the explantion wasnt as boring as it first seemed lol, but if you want to make it seem believable without looking at game mechanics you need to remember that the creeper wont evaporate because the inner parts of the pool still have a bit of creeper therefore it is the source, once you've drained it to the point where its incredibly thinly spread then it will begin retreating on its own, but its true that a pool with no edge will never evaporate, it needs somewhere to expand the remaining build up of creep before it disappears

(maybe i'll try and get a screenshot showing the creeper expanding and then retreating on its own if it helps)

and i'd very much like to be a beta tester too, cant wait to get my hands on the map editor

[knucracker]

You're in luck on the map editor.  It's been released and is just waiting on folks to grab it and come up with some interesting maps.
http://knucklecracker.com/creeperworld/viewmaps.php

Just click the "Download Map Editor" link in the upper right hand corner of the page.

I also think I will start a thread for 'best practices' on making maps.  Just some hints to help people get started on making fun and challenging maps.  Making good maps is kind of an advanced 'game' in its own right.

[Aurzel]

yep got it and already took a little dabble at it, reminds me of the starcraft map editor just more toned down and its pretty great

and i agree with that, and there should also be a section in there where we can review the maps sent in

[thepenguin]

I always wondered about this

[F0R]

Wait a beta group where?

[UpperKEES]

I always wondered about this

Wait a beta group where?

;D

[Aurzel]

wow major thread rez there lol
but then again what virgil said is very important for any new players :P