01-31-2017, 12:32 PM | #1 |
Join Date: Jun 2013
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[RPM] Potential Energy
... or, how to make falling boulders and boxes of explosives in RPM.
This thread is inspired by this ritual and the problem it raises. I think I actually have a relatively simple solution. See, the issue isn't so much creating a big boulder that can fall on and smash people - it's creating one up in the sky above the character. After all, if someone were to create a boulder right beside them, then push it off a cliff, that doesn't seem an illegitimate option (it's just like being able to create a club without needing to pay for the damage your ogre friend will do with it). Essentially, in addition to just creating a big chunk of rock, you are also creating it with a massive amount of potential energy, calling for Create Energy. Whether this is Lesser or Greater is up to the GM - you might want to follow the damage guidelines from Destroy Matter. At first, my idea was to add a surcharge to the ritual to account for such energy, but it occurred to me that the Create Advantage actually gives a more-or-less balanced matter-energy equivalence*, which works out to every 100 kJ of energy being worth 1 lb of matter. This should also be doable for explosives and batteries/power cells. Call it Potential Energy for objects created at a great height, Stored Energy for explosives and batteries/power cells. After doing some unit conversions and simplifying, I've got the equations needed. For adding potential energy (such as creating a boulder 50 yards in the sky, as in the example ritual), use w*h*g/4000, where w is weight in lb, h is height in yards, and g is gravity in G's (1 on Earth), to determine how many lb-equivalents of energy you need to add. For explosives, this is instead 20*w*REF (every pound of TNT has around 2000 kJ in it). In either case, you must pay for both the weight of matter you create and the weight-equivalent of energy you add to it. So, for that Bridge Breaker Charm, you're looking probably looking at Greater Create Energy (6) + Lesser Create Matter (6) + Lesser Control Magic (5) + Subject Weight, 50 tons (8) + Potential Energy, 1250 lb (5) + Range, 50 yards (8) + Duration, 10 minutes (1)**, for a total of 117 energy (39x3), which seems more appropriate. For a Conjure C4 ritual that makes a 8 of the typical 1.25 lb blocks of C4 that lasts for up to a day, each 1.25 lb block of C4 contains energy equivalent to 35 lb of Subject Weight, so you're looking at Greater Create Energy (6) + Lesser Create Matter (6) + Subject Weight, 10 lb (0) + Stored Energy, 280 lb (3) + Duration, 1 day (7), for a total of 66 energy (22x3). You'd later detonate them either with normal blasting caps or a Lesser Create Energy ritual. Optionally, a character can use Path of Matter in place of Path of Energy here (to make a character who can create boulders up in the sky but not fireballs). This is probably a trait worth [5] or so to do so for Potential Energy, but I generally wouldn't make it available for Stored Energy (if it is, maybe another [5] there). Optionally, only allow such characters to do this with rituals for which they either have a Grimoire or Ritual Mastery. Note the ritual that doesn't use Path of Energy is distinct from the one that does. If you'd prefer, multiply the above equations by 100 (the first becomes 25* rather than /4) to get Potential/Stored Energy in kJ, and multiply the weight column of the Spell Modifiers Table by 100 to change from lb to kJ. Of course, that can result in some pretty big numbers to look at, so you might instead want to divide by 10 in each case to turn things into MJ. The table would change to this: Code:
Poten/Stored Added Energy 1 kJ +0 3 kJ +1 10 kJ +2 30 kJ +3 100 kJ +4 300 kJ +5 1 MJ +6 3 MJ +7 10 MJ +8 … … (x1000) (+6) *E=mc^2 doesn't work here, because it means the 10 lb object you can make without adding any energy is worth something like 80 PJ, if I've done my math right. That's a bit over the output of the Tunguska event. **Allowing "Momentary" to last long enough for the boulder to hit the ground doesn't seem like a stretch to me, but would only reduce the cost of the spell to 114 energy (38x3). Last edited by Varyon; 03-25-2021 at 08:09 AM. Reason: correcting J/kJ SNAFU |
01-31-2017, 12:49 PM | #2 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [RPM] Potential Energy
The fundamental problem is that damage and weight are on completely different scales. Plausibly speaking, 'transform' and 'destroy' should be the same magnitude of effect, which means if we leave the weight table alone, we should actually have a damage table sort of like this
Code:
Energy Weight Damage -2 1 lb 1d -1 3 lbs 1d+2 0 10 lbs. 2d +1` 30 lbs. 3d +2 100 lbs. 4d+2 +3 300 lbs. 7d +4 1,000 lbs. 10d +5 3,000 lbs. 15d +6 5 tons 20d +7 15 tons 30d +8 50 tons 45d +9 150 tons 70d +10 500 tons 100d |
01-31-2017, 01:15 PM | #3 | ||
Join Date: Jun 2013
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Re: [RPM] Potential Energy
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I'm curious, however, as to how you came to your table. At first it looks like you're assuming an REF .0028 or so explosive for the 10 lb -> 2d figure (consistent with 0 energy for a 2d external explosive), but in that case 1,000 lb of it would do 20d damage, not 10d. (EDIT: Upon a second review, it looks like you're more-or-less scaling things as +1 SSR to damage per +3 SSR to weight, which would be consistent with scaling explosive damage to the cube root of weight instead of the square root. Is that the case here?) Quote:
(EDIT: Updated) Last edited by Varyon; 01-31-2017 at 01:32 PM. |
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01-31-2017, 02:41 PM | #4 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [RPM] Potential Energy
I started at a base of 'a damage effect should break an unliving object of equal mass' and then rebased it slightly to 1 lb = 1d. Thus, a 1,000 lb unliving object (40 hp) corresponds to a 10d attack (35 damage).
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01-31-2017, 03:40 PM | #5 | |
Join Date: Jun 2013
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Re: [RPM] Potential Energy
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I'll give it some thought. It would certainly make things more concise than the current methodology I've suggested. |
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01-31-2017, 04:39 PM | #6 | |
Join Date: Jan 2017
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Re: [RPM] Potential Energy
I am very pleased to have spurred such an interesting debate.
I would imagine that making Gunpowder is not possible with lesser as it is an EXACT chemical mixture. Even if we give it that. Using Greater Create Matter, three times with a duration of 1 day(39 energy each). Will create the ingredients of Blackpowder. Now to my original intent. Based on your critique (MUCH appreciated). Here is the renewed effort. I even went so far as to compute the Size of the beast. Quote:
EDIT: The reason to not decrease the Duration is the "secondary effects" of the such a large and heavy object interacting with the world. Even if I choose not to use such a High weight. Controlling the shape to have a narrow base and wide top would still have the desired effect. Moreover making a multi-ton cylinder would be able to accomplish the goal also. All this is fun. But the real truth is that a Transform matter at the base of a bridge would be all it would take to wipe it out. Which leads me to believe a clever Ritualist would never have to use more than 50 EP to cause utter destruction. Ok. So update: The 3 rules Ask if it possible for A person could do it by themselves if it takes a long time and equipment, possible. If any are yes then it might be Greater, if 2 are yes. it is Most Likely Greater. 3 is clearly a greater or more. Last edited by AnkhLord; 02-01-2017 at 01:35 PM. Reason: Idea after posting. Found other rules. |
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01-31-2017, 10:36 PM | #7 |
Join Date: Aug 2008
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Re: [RPM] Potential Energy
I would generally avoid any calculations of energy or energy-pressure generated by the falling object, just as I would avoid checking the shear modulus for the wooden beams or measuring the length of time of contact between the boulder.
The number one rule of RPM is that it is a Rule Zero system. If the intent of casting the spell is to inflict a bunch of damage, the vehicle by which said damage is delivered is irrelevant, especially if that vehicle will blink out of existence right after dealing that damage. As such, this is simply adding the Damage modifier to the spell with sufficient quantity and modifiers to represent a massive falling boulder. That it creates a massive falling boulder simply gives the option to cast this as a Create Matter effect instead of a Destroy Matter effect. I'd allow either for this sort of thing, personally, but others might be more stringent. If the boulder is to stick around afterward for a while, I'd treat this as two effects: Create Matter (to make a semi-permanent boulder) and Destroy Matter (to trash the bridge/squash the troll/etc.). Personally, I'd be curious to hear how PK would adjudicate this situation.
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02-01-2017, 11:20 AM | #8 | |||
Join Date: Jun 2013
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Re: [RPM] Potential Energy
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Of course, if someone wants to use the normal Damage modifier for a similar ritual, like a rain of stones, I'm fine with that. |
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02-01-2017, 11:50 AM | #9 |
Wielder of Smart Pants
Join Date: Aug 2004
Location: Ventura CA
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Re: [RPM] Potential Energy
If you made the rock at your altitude and just dropped it, that would probably require a Dropping roll to hit.
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02-01-2017, 02:01 PM | #10 | |
Join Date: Jan 2005
Location: Gothenburg, Sweden
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Re: [RPM] Potential Energy
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Tags |
ritual path magic, rpm |
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