MechWarrior Online Heat Mechanics Guide



MechWarrior Online Heat Mechanics Guide by Amaris the Usurper

Edit (November 2nd): My main purpose in starting this thread was to expose some (probable) bugs through experimental testing. The guess that the ItemStats.xml “heat” values were being used as rates of heat generation (instead of total heat generated) for small, medium, and large pulse lasers, as well as small lasers, was correct. Also, after the November 6th patch, double heat sinks (including those in the engine) will dissipate 0.14 heat/second, not 0.2 (as would be consistent with the TT game). Finally, weapon heat generation, beam duration, and cooldown time will become more transparent in the future; see http://mwomercs.com/…e-improvements/. Keep this in mind when reading. I will produce an updated guide to heat behavior once things have settled down.

TL:DR/Summary

Single and double heat sinks should probably dissipate 0.1 and 0.2 heat/second, respectively (i.e., they are probably intended to be coded this way). [Edit: This has been confirmed by the devs.] Medium and large pulse and “beam” lasers produce roughly the same amount of heat per shot. The values in ItemStats.xml, used in Ohmwrecker’s tables, may not be used by the game at all, or they may be used in a complicated way. As noted by the devs, double heat sinks in the engine aren’t fully effective. This is also the case when using single heat sinks with an engine that has zero or more heat sink slots, and no additional heat sinks are fitted (new finding). So, for example, if you have at some point switched from 11 to 10 heat sinks on your Catapult’s 260 standard engine and been very disappointed with its ability to dissipate heat, you are probably not alone.

Long Version

[Disclaimer: Rudimentary knowledge of calculus required to fully “get” it. Brace yourselves.]

In what follows, I attempt to shed some light on these questions:

  • How (in general) does the heat mechanic work?
  • How much heat do the different weapons produce?
  • How effective are heat sinks?
  • Is there anything “bugged” about engine heat sinks beyond the already-noted double heat sink issue?

Theory of the Heat Mechanic

I hypothesize that the heat level changes at a rate

dH/dt = RHG-RHD

down to a minimum of zero, where:

H = absolute (not %) heat level of mech (number of heat points currently carried);
RHG = rate of heat generation by weapons;
RHD = rate of heat dissipation by heat sinks;
t = time (in seconds).

While this has never (to my knowledge) been stated by the devs, I think it summarizes how most of us (especially those familiar with the TT game) intuit that the heat system should work. Note that I have not yet said anything about how RHD depends on the number of heat sinks (or other factors).

Integrating the expression for dH/dt between t = 0 and t = T, we get

0 = THG-THD => THG = THD,

where THG and THD are the total number of heat points generated and dissipated, respectively. This expresses the obvious fact that, if H begins and ends at zero, the number of heat points generated must equal the number of heat points sinked.

Now, based on my observations in MWO (and consistent with the TT game), it appears that we should have

RHD = 0.1*NHS

for single heat sinks, and

RHD = 0.2*NHS

for double heat sinks, where NHS is the number of heat sinks carried. Thus,

THD = 0.1*NHS*T,

or

THD = 0.2*NHS*T,

depending on the type of heat sinks, and provided the heat scale stays above zero.

Edit: The values of 0.1 and 0.2 for SHS and DHS are correct. Thanks, Culler.

Obviously, all of the above assumes continuous behavior of what must, in reality, be a time-discrete process. Let’s just assume that the time increment is small enough that the continuous model is accurate.

Now for some justification. First, this is how things work in the TT game: one heat sink dissipates one heat point over ten seconds. Second, one can do some data mining and find an XML file (ItemStats.xml) containing weapon stats (including heat generated, beam duration, recycle time, etc.), which have been incorporated into popular tables by Ohmwrecker. The results I have found are not in agreement with a naive interpretation of the values contained therein (see below). The major point is that we do not know how or even if the game uses these stats. Because of this, we shouldn’t reject ideas about how the heat system works solely because they are inconsistent with some other idea of what the numbers in ItemStats.xml mean. The important thing is the experimental data.

Mech Heat Capacity and the MechLab “Heat Efficiency” Statistic

As previously noted by others, the heat “capacity” (HC) of a mech (i.e., the amount of heat points that will cause shutdown) appears to be

HC = 30+NHS

for single heat sinks, and it probably should be

HC = 30+2*NHS

for double heat sinks.

Edit: Zyllos has done a test (in an Awesome) that appears to contradict the above formula for HC with single heat sinks. However, I later repeated his test (in a Catapult) and found results consistent with the formula, although I initially screwed up the analysis and got a wrong conclusion. That has been fixed. I have not repeated Zyllos’s test, as I don’t own an Awesome. If someone who does could try to repeat it, that would be great. See posts 8 and 11.

The “Heat Efficiency” statistic in the MechLab is also of interest. Its behavior has been decoded and is discussed here: http://www.reddit.co…ing_worked_on/. Based on experimental evidence, the number displayed in the MechLab does not appear to give a useful indication of the heat sinks’ ability to dissipate the heat generated by weapons fire. At present, it should probably be ignored.

Methodology, Results, and Discussion

I have performed in-game tests, using a stopwatch along with the above equation for single heat sinks, to determine THG for various energy weapons. So far, I have only tested mechs with single heat sinks and standard engines. The results are somewhat consistent with a certain interpretation of the values contained in the XML file, but this is not conclusive (yet; see below).

These are not the only discrepancies, however. It appears that, for engines that have zero or more heat sink slots, the engine heat sinks operate at reduced effectiveness until at least one additional heat sink is added and placed outside the engine. This probably should not be happening. (The problem may also be fixed by placing heat sinks inside the engine, when possible, but I have not tested this.) Consistent with the above, I have not observed any discrepancies for engines that require at least one heat sink to be placed externally in order to connect to a match (e.g., the 245 standard in the Jenner).

I have used the hypothesis above about how the heat mechanic works to calculate the heat produced per weapon. Basically,

THG = THD,

or, equivalently,

[number of salvoes]*[number of weapons]*[heat per weapon] = 0.1*NHS*T,

so that

[heat per weapon] = 0.1*NHS*T/([number of salvoes]*[number of weapons]),

where T was determined by recording the time the heat scale took to go from zero to zero with a stopwatch. Care was taken to ensure that the heat scale remained positive at all times, so that the heat sinks were always functioning and THD = 0.1*NHS*T was valid. All tests were performed out of the water on Forest Colony, Frozen City, or River City and with the throttle set to zero. There exists a general consensus that these three maps have the same heat effects.

The experimental results follow, although there are not yet enough to draw strong conclusions. I regret that they are not as complete or systematic as they could be, but I have limited time.

First comes an assortment of tests using mechs with heat sinks placed outside the engine. These don’t really form part of my argument and are just here for reference/use in future discussion. The numbers are the times taken for the heat scale to “zero” (i.e., T) for the different tests. They were averaged and then used in the formula above.

CPLT-C1(F)
standard engine 260
25 single heat sinks
12 salvoes of 2 large pulse lasers
River City
69.0. 68.8, 69.1, 68.9 => 69.0 average => 7.18 heat/laser

CPLT-C1(F)
standard engine 260
31 single heat sinks
20 salvoes of 2 large lasers
River City
99.9 => 7.24 heat/laser

AWS-8T
standard engine 240
23 single heat sinks
10 salvoes of 2 large lasers
63.0, 63.2, 62.8, 63.2 => 63.1 average => 7.25 heat/laser

CN9-AL
standard engine 200
16 single heat sinks
20 salvoes of 2 medium lasers
Forest Colony
103.3 => 4.13 heat/laser

CN9-AL
standard engine 200
16 single heat sinks
10 salvoes of 2 medium lasers
River City
52.0, 52.0, 52.1 => 52.0 average => 4.16 heat/laser

Now for the important part. These are tests of medium pulse lasers using the Catapult. Around 4 heat appears to be generated for all numbers of heat sinks except 10 (no heat sinks outside the engine), where the number is instead around 5. However, in that case, assuming that only 8 of the stated 10 engine heat sinks are actually working, we again find around 4 heat generated. Given that the lasers should produce the same amount of heat regardless of the number of heat sinks carried, this should not be happening.

CPLT-C1(F)
standard engine 260
10 single heat sinks
2 salvoes of 4 medium pulse lasers
River City
38.4, 39.9 => 39.2 average => 4.89 heat/laser
but if we assume 8 engine heat sinks => 3.92 heat/laser

CPLT-C1(F)
standard engine 260
10 single heat sinks
2 salvoes of 4 medium pulse lasers
River City
40.7, 39.9, 38.5, 40.0, 40.0, 39.9 => 39.8 average => 4.98 heat/laser
but if we assume 8 engine heat sinks => 3.98 heat/laser

CPLT-C1(F)
standard engine 260
11 single heat sinks
2 salvoes of 4 medium pulse lasers
River City
29.6, 29.3, 29.4, 29.6 => 29.5 average => 4.05 heat/laser

CPLT-C1(F)
standard engine 260
12 single heat sinks
2 salvoes of 4 medium pulse lasers
Frozen City
27.0, 26.9, 27.2, 27.0, 27.0, 27.0, 27.1, 26.9 => 27.0 average => 4.05 heat/laser

CPLT-C1(F)
standard engine 260
31 single heat sinks
14 salvoes of 4 medium pulse lasers
River City
72.4, 72.3, 72.2 => 72.3 average => 4.00 heat/laser

Here are similar results, except for the Atlas and this time using medium lasers. We again find 5 heat generated for 10 single heat sinks (no heat sinks outside the engine) but 4 for 11 heat sinks (one outside the engine). Again, assuming that only 8 heat sinks are effective corrects the discrepancy. I have not performed more tests, because I installed double heat sinks on my Atlas last night, and I don’t want to pay to remove/reinstall them. You are welcome to perform more and post the results here. This would also be a good opportunity to see if adding a heat sink to the engine also fixes the discrepancy. My guess is that the same thing is happening as with the Catapult using medium pulse lasers, however. Also, notice how comparatively “glitchy” the numbers are for 10 heat sinks compared to 11. I’m not sure whether this is repeatable or just a client/server communication issue.

AS7-D(F)
standard engine 300
10 single heat sinks
2 salvoes of 4 medium lasers
River City
38.9, 40.2, 42.5, 39.1, 46.7, 39.4, 40.4, 38.7, 43.8, 40.8 => 41.1 average => 5.13 heat/laser
but if we assume 8 engine heat sinks => 4.10 heat/laser

AS7-D(F)
standard engine 300
10 single heat sinks
2 salvoes of 4 medium lasers
Forest Colony
37.4, 39.8, 39.3, 39.0, 41.6, 38.3, 38.6 => 39.1 average => 4.89 heat/laser
but if we assume 8 engine heat sinks => 3.92 heat/laser

AS7-D(F)
standard engine 300
11 single heat sinks
2 salvoes of 4 medium lasers
River City
30.5, 30.7, 30.5, 30.7, 30.6, 30.7 => 30.6 average => 4.21 heat/laser

In the following three tests, I again used a Catapult, but instead tested small lasers. They appear to produce around 1.6 heat. The discrepancy with no engine heat sinks is again observed and can be corrected as before.

CPLT-C1(F)
standard engine 260
10 single heat sinks
6 salvoes of 4 small lasers
River City
51.8, 50.6, 49.4 => 50.6 average => 2.11 heat/laser
but if we assume 8 engine heat sinks => 1.69 heat/laser

CPLT-C1(F)
standard engine 260
11 single heat sinks
6 salvoes of 4 small lasers
River City
35.2, 35.3, 35.6, 35.5, 35.2 => 35.4 average => 1.62 heat/laser

CPLT-C1(F)
standard engine 260
16 single heat sinks
10 salvoes of 4 small lasers
Forest Colony
40.3, 40.4, 40.1, 40.1 => 40.2 average => 1.61 heat/laser

Additional Discussion: Interpretation of the Values in ItemStats.xml

Averaging across the various tests (except for those with only engine heat sinks) for the different weapons tested and rounding to the nearest tenth, we find the following results for total heat generated per weapon:

small laser: 1.6
medium laser: 4.2
large laser: 7.2

small pulse laser: n/a
medium pulse laser: 4.0
large pulse laser: 7.2

The XML file gives different values in the “heat” field. It has been suggested that this field really indicates the rate of heat generation, so that the total heat generated would be given by the number in the “heat” field times the number in the “duration” field. Thus we would have:

small laser: 2 “heat”, 0.75 “duration” => 1.5 total heat;
medium laser: 4 “heat”, 1 “duration” => 4 total heat;
large laser: 7 “heat”, 1 “duration” => 7 total heat;

small pulse laser: 3 “heat”, 0.5 “duration” => 1.5 total heat;
medium pulse laser: 5 “heat”, 0.75 “duration” => 3.75 total heat;
large pulse laser: 9 “heat”, 0.75 “duration” => 6.75 total heat.

These numbers are much closer to the computed results than are those in the “heat” field. However, the fit is still not all that great. I am tempted to explain this away as error introduced by client/server communication issues, but I deliberately took measurements over long time periods (> 25 s) to minimize this problem. More data are needed to draw any strong conclusions.

Future Work

All of the above pertains to “normal” maps (i.e., not Caustic Valley) and “normal” conditions (i.e., zero throttle, not jumping, and not standing in water). It is possible that each of these conditions incurs a proportional reduction in the number of effective heat sinks (i.e., the total is reduced by a given percentage). Once the bugs are ironed out and we have a good idea of how much heat each weapon actually produces, these would be good things to look into.

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