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The purpose of heat from a game design perspective is to give the player a resource to manage during play--a player can fire a lot of weapons, taking a long cool-off period in between, or fire fewer weapons continuously. In practice, players will do both, choosing the right moment (hopefully) to strike a decisive blow at the risk of leaving themselves vulnerable.
While in a match, the current mech heat level is displayed to the right of the minimap. In the mechlab, a heat management value is provided for the active mech. This value indicates a ratio of the mech’s ability to generate heat versus it’s ability to dissipate heat. I’m not entirely sure of the math behind it, but I’d say any mech with a value under 1 will run hotter than you probably want and those near 2 will run cool.
Heat Generation
Many things in the game can generate heat, but by far the most heat is generated by the mech firing its weapons. Each weapon has a value for the amount of heat it generates when fired and this information is available in the game mechlab and on 3rd party sites like Smurfy. When you fire a weapon, that weapon’s heat value is added to the total heat of the mech. Heat is one of the factors that differentiate weapon types. Energy weapons generate a lot of heat, Missiles and Ballistics generate much less.
Being struck by an enemy’s weapon does not generate heat on the target, with the exception of the flamer weapon type. Flamers cause slight heat on the target--not enough to build significant heat but enough to prevent heat dissipation on the target.
Using Jump Jets generates a slight amount of heat. Each jump jet installed on a mech adds heat during use. While the amount generated is slight, using jump jets will prevent a mech from dissipating heat while the jump jets are active.
Environmental factors can generate heat. Each map has an overall environmental temperature, given on the loading screen, which sets the base heat for mechs on that map. Basically the map heats mechs to a certain baseline temperature, preventing the mech from cooling itself below that point. This has the effect of reducing the mech’s heat capacity for that match.
Some maps have regions of higher than normal heat, and in the case of lava this heat is enough to exceed a mech’s cooling capacity, creating a situation where the environment can overheat a mech.
Simple movement also generates a slight amount of heat. Standing still generates no heat. Moving up to ½ throttle generates about 1 heat per second, from ½ to ¾ generates slightly more heat and from ¾ to full throttle generates about 2 heat (NB: these values are estimates on my part. Links to better data appreciated).
Heat Sinks
A mech dissipates heat through the use of heat sinks. Heat sinks reduce the mech’s stored heat at a certain amount per second until the heat baseline for that environment is reached. Heat sinks also increase the heat capacity of a mech, raising the heat level that causes a heat shutdown (Note: mechs have an intrinsic heat capacity of 30 before considering heat sinks).
All mechs have a minimum of ten heat sinks. This is not obvious because each engine has a certain number of intrinsic heat sinks which aren’t displayed by the game mechlab. The mechlab will warn you if a particular engine requires additional heat sinks to be valid--this number subtracted from ten will provide the number of intrinsic heat sinks on that engine.
Heat sinks may also be added to the mech loadout as modules fitted to critical slots. Some larger engines also provide heat sink slots, referred to in the mechlab as ‘Int. Heatsinks’ (Internal?). Installing a heat sink in an engine’s internal slot does not take up a critical slot on the mech but the weight of the heat sink is counted towards the total mech weight.
There are two types of heat sink: Standard and Double. Most Inner Sphere mechs come with standard heat sinks by default. Clan mechs come with clan double heat sinks by default.
A standard heat sink (SHS) adds 1 to the heat capacity of the mech (thus the minimum heat capacity in the game is 40: 10 from the minimum heat sink requirements plus the 30 from the intrinsic heat capacity mentioned above). A standard heat sink dissipates 0.1 heat per second, or 1 heat per second for the minimum 10 required heat sinks. Standard heat sinks weigh one ton and require one critical slot when installed outside the engine.
Double heat sinks (DHS) are an improvement to standard heat sinks and are found on the mechlab upgrades menu. Single and double heat sinks cannot be mixed on a single chassis. Double heat sinks add 1.4 to the heat capacity of the mech. Double heat sinks installed as modules dissipate .14 heat per second. When a mech is upgraded to use double heat sinks, the intrinsic engine heat sinks are able to dissipate .2 heat per second as an added bonus over standard head sinks. I am unsure as to whether DHSs installed in engine heat sink slots get same the cooling bonus as the intrinsic engine heat sinks.
Inner Sphere double heat sinks weigh one ton and require three critical slots when installed outside the engine. Clan DHSs also weigh one ton but only require two critical slots.
In almost every case, all IS mechs should be upgraded to double heat sinks. The cooling benefit, especially from the ‘free’ heat sinks in the engine is just too great. Consider the cost of the mech to be 1.5M C-Bills more than the list price.
Impact of Environment on Heat Sinks
Unfortunately (or interestingly) heat dissipation is more complicated than this. The actual heat dissipation of a mech is strongly influenced by the environmental effects of a map. The numbers given above are only accurate in the abstract. In practice, each map provides a bonus or malus to both the dissipation rate and heat capacity. This post provides some interesting experimental data on this effect. For example, a ‘hot’ map might provide a -25% effect to dissipation and capacity.
I suggest using the in-game Testing Grounds and online tools such as this to evaluate how much cooling is required for a particular build.
Heat sinks installed in a mech’s legs also gain a bonus to cooling when the mech is walking through water deep enough to submerge the legs. I believe submerging heat sinks doubles their effectiveness and that this bonus scales to the amount of leg that is underwater. Note that due to critical slot constraints only SHSs are usable in the legs of IS mechs.
Heat Scaling/Ghost Heat
MWO has a game balance mechanic called Heat Scaling by PGI and ghost heat by much of the community. The purpose of this mechanic is to help balance the game by penalizing mech builds that take large numbers of a certain weapon type (‘boating’).
The way heat scaling works is that each weapon is assigned to a group (this group information can be found listed on Smurfy). Each group has a cap on the number of weapons that can be fired simultaneously at no penalty. For the purposes of heat scaling, simultaneous means within .5 seconds of each other--weapons fired at more than .5 second intervals are unaffected. Up to this cap, firing weapons as a group generates the normal amount of heat for those weapons. But if a number of weapons are fired that are over the cap, each additional weapon generates more heat than normal.
For example, firing one IS Large Laser generates 7 heat. The group containing the IS Large Laser has a cap of two. So two LLs, fired together, will generate 7 x 2 = 14 heat. However three LLs exceeds the cap and firing 3 LLs creates not 24, but 24.53 heat. Heat scaling increases significantly as the number of weapons grows. Smurfy’s has a nice chart.
The in game mechlab will give a warning if you have loaded enough weapons from a group to be subject to heat scaling.
In moderate cases, heat scaling has a mild effect. But players should be aware as the effect becomes a significant penalty when the group cap is exceeded by a large number of weapons.
Here is PGI’s description of the mechanic.
Overheating
If your mech’s heat exceeds its heat capacity, the mech will overheat. While overheated, the mech takes periodic damage to the center torso. This damage ignores armor and can cause critical hits. The damage continues to be applied until the mech drops below 100% heat capacity. This damage increases the further the heat level is above the heat capacity of the mech.
The player is given audible and visual warnings when the heat level exceed 80% capacity.
In the absence of player input, a mech which exceeds its heat capacity will shut down. While shut down, the mech is inactive and unresponsive to player input. The mech will cool at the normal rate for an immobile mech while it is shut down. When the mech drops to 90% heat capacity it will automatically restart.
The player may override the automatic heat shutdown with the override keybinding. This may be activated prior to automatic shutdown being triggered. If the mech exceeds 100% heat capacity within five seconds after the override is engaged the mech will the mech will continue to operate above its 100% heat capacity. The override may also be engaged after shutdown to hasten the restart process. Due to overheating damage, use of the override is dangerous and can cause th mech to self-destruct.
Managing Heat
Managing heat is one of the most important player skills in MWO. There are a number of ways to help do it.
The first step to managing heat happens in the mechlab. It is desirable to outfit mechs to be a heat-neutral as possible. Often, a mech with fewer or smaller weapons will be a more efficient damage-dealer as it is able to fire weapons almost continuously. Taking the most and largest weapons is not always a workable design. Energy weapons generate a lot of heat--mix in Ballistic or Missile weapons when available.
Next, it is possible to divide the weapons on your mech into different weapons groups and fire them via a separate trigger key. This can be done in the mechlab or on the Training Grounds (using right Ctrl and the cursor keys). Please don’t set weapon groups in a match. Use the Training Grounds. Remember the heat scaling rules listed above--if you have weapons subject to heat scaling you can break them into smaller groups and fire them .5 seconds apart to avoid the effect.
Each weapon group can be switched to chain-fire (default keybinding is Backspace). When in chain-fire mode each trigger press will fire one weapon in the assigned weapon group at a time, one per trigger press. This can significantly reduce heat buildup. It is often helpful to have duplicate weapon groups (two groups containing the same weapons) and set one to chain-fire. This allows the pilot to fire with the whole group until heat becomes an issue then switch to the chain-fire group to cool down.
There are two mech skills that effect heat: Cool Run and Heat Containment. Cool Run increases the mech’s heat dissipation by 7.5%. Heat Containment increases the heat capacity by 10%. Both are basic-level inexpensive skills. Remember that when you unlock all elite-level skills for a chassis, you receive a 2x bonus to the effects of basic skills, so eliting grants a 15% bonus to cooling and a 20% increase to the heat capacity.
Careful aim is also a large part of heat management. Because there is a heat cost every time you fire most weapons, a missed shot has an opportunity cost associated with it--you’ve essentially spent heat capacity which is now unusable until you cool down. Thus it’s worth taking the time to line up shots and resist the urge to snap fire every time an opportunity presents itself unless you are confident of a solid hit.
The above tips and prudent piloting should be sufficient to manage heat. There are, however, consumable modules called Cool Shots which can be purchased from the mechlab’s modules menu that may be useful in critical situations. Each Cool Shot has a numerical value (6/9/18) which gives the amount of cooling each shot delivers (e.g., a Cool Shot 6 will cool your mech by 6 heat points). The Cool Shot 6 and 9 are purchasable for C-Bills while the 18 is an MC item. Oddly, only one type of Cool Shot can be installed on a mech at a time (i.e., a 6 and 9 are permitted, but 2 Cool Shot 6’s are not).
There are global skills unlockable for GXP that effect Cool Shots. One increases the effect of Cool Shots by 20% and the second doubles the effect of the 9 shot, essentially giving you the ability to have a C-Bill Cool Shot 18.
This is one of a series of articles on concepts in MWO. If you found this article helpful, you may wish to read the other articles listed in this post.
Edited by Gauvan, 09 January 2015 - 11:22 AM.
