Converting Shadowrun Magic to GURPS

[Crakkerjakk]

Originally Posted by Jürgen Hubert

I'm still divided over that. Some people should have an easier time resisting drain than others, but basing everything on Will would probably be too unbalancing, unless you are okay with all PC mages running around with Will 20.


Some further thoughts on how to do the conversion:

I will largely go with the Shadowrun 5E rules, since they are the most recent and more flexible damage levels are easier to port than the four damage levels of Shadowrun 3E and earlier.

In Shadowrun 5E, an "average human" has 10 physical damage boxes. After that, he becomes "dying".

In GURPS, I will thus treat those 10 physical damage boxes as 20 hit points, with each box representing roughly 2 hit points.

For statistical analysis purposes, I will assume that each Shadowrun die equals 1/3 of a "hit", or success. Thus, an average human - with a value of "3" in all attributes - will have one hit on most resistance tests.

I don't think it should be a design goal to match specific outcomes from one set of mechanics to the other. I mean, trolls should be able to shrug off quite a few light pistol hits, but the exact same amount as SR is unnecessary, IMO. I'd feel the same about spell damage levels.

I like the idea of Force capping MoS.

[Jürgen Hubert]

Basically, 20 points of damage would be my base value for "how powerful has this spell to be to take out an average guy with one hit". Let's examine some Shadowrun spells and translate them into GURPS states (complete with character point totals) and see if we can figure something out - since the damage types for GURPS are far more flexible than those for Shadowrun, it is my hope that we can come up with a system for far more flexible spell attacks based on Innate Attack than what is possible with the Shadowrun rules.

Let's start with a "Mana Bolt". It only damages physical objects, which makes it Toxic damage [4/level] - but we need to do 6d-1 toxic damage to get an average of 20 damage, which makes the base cost 4 x 5.7 = 22.8 CP.

It ignores all armor, which makes it a Malediction - and since it is Line of Sight, we give it the long-range modifier (+200%). Mana spells also Affect Insubstantial targets (+20%), which brings the total to 73 CP.

This is the equivalent of a Force 10 manabolt which has attained 10 net successes (a tall order for a spellcaster, but let's leave that aside). This would have a drain value of (Force -3) = 7.

A "Power Bolt" would look fairly similar, but start out with either "crushing" or "piercing" damage for 5 CP/level. For 20 damage this would increase to 5 x 5.7 = 28.5 CP, which (with the Malediction, but without Affects Insubstantial) brings us to a total of 86 CP.


Now let's get to "indirect" spells that create a physical force instead of working like a malediction - picking the "Flamethrower" spell. This is burning damage, for 5 CP/level which again brings us to 28.5 CP for the base damage. Furthermore, it counts as "Guided" (+50%) since there are no range penalties. While it is hard to model attacks with infinite range in GURPS, let's say that this spell has a range of 200 yards, which is sufficient for most purposes. Starting out with the 10 yards for 1/2 D and the 100 yards for Max, we need to bring both of these values to 200 so that the spell reaches that far (+5%) and can hit the target within one round (+20%). Furthermore, indirect combat spells in Shadowrun are armor-piercing by default - so let's give it an Armor Divisor of (2), for +50%. This adds up to a total of 65 CP.

As an indirect spell, a Shadowrun mage casting "Flamethrower" needs to end up with a Damage Value of 11 (since the average human with Body 3 will roll one success in resisting the damage). This is doable with Force 6, resulting in a drain value of (Force - 3) = 3.

[Jürgen Hubert]

So what's my take from all this math? Well, I think my suggestion for linking force and drain reduction on the success test is a good one. However, this will also make it somewhat harder to reduce Drain in GURPS than it is in Shadowrun - since if you don't manage to reach a Margin of Success higher than your Force, your Drain won't be reduced at all.

So, assuming that we treat Shadowrun Stun damage and GURPS Fatigue as identical (which should work reasonably well - an "average human" has 10 of either), then the Fatigue values should be slightly lower in the GURPS rules than their equivalent drain rules.

Right now, I am considering 15 CP in an Innate Attack = 1 point of base Fatigue. Furthermore, you need 1 level of spell Force for each 15 CP in Innate Attack you want to deploy - and if you fail to reach a Margin of Success equal to your Force, the Innate Attack acts as if it was worth less CP.

This of course would mean that we would have to create tables for spell effects - listing the damage / other effect for each point of MoS reached.

This rule might also be extend-able to other spell effects - figure out what the CP value should be, and derive the fatigue cost based on that (as well as what the required Force levels would be).

Finally, I think 5 CP per spell learned would be a good costs for spells.


What do you think so far?

[Crakkerjakk]

Use standard costs for Magery? Magery is a direct 1:1 replacement for a Magic attribute?

[Fred Brackin]

Originally Posted by Jürgen Hubert

Let's start with a "Mana Bolt". It only damages physical objects, which makes it Toxic damage [4/level] -

No, Characters p.62 specifies that Toxic damage never affects Machines. Machines are "physical objects" so Mana Bolt can not be Toxic.

For "generic" damage I think you might be looking for Crushing with No Knockback

[Jürgen Hubert]

Originally Posted by Crakkerjakk

Use standard costs for Magery? Magery is a direct 1:1 replacement for a Magic attribute?

I don't see why we shouldn't use Magery, although we will probably need some additional advantages for the astral perception/projection stuff. Not to mention Metamagic...

Since Shadowrun skills are rather broad when compared to GURPS, it might also be a good idea to split it into five different skills representing the five different types of spells - Combat, Detection, Illusion, Healing, and Manipulation.


But first, let's see how this "15 CP = 1 point of Spell Force" works out for non-combat spells! Starting with "Magic Fingers", the standard "Telekinesis" spell. Considering that the Shadowrun spell has a range of Line of Sight, and the GURPS advantage "Telekinesis" a range of only 10 yards, we will want to increase that to 200 yards or so (+40%). Thus, our MoS table gives us:

MoS - GURPS advantage

0-1: Telekinesis with ST 2 (14 CP)
2: Telekinesis with ST 4 (28 CP)
3: Telekinesis with ST 6 (42 CP)
4: Telekinesis with ST 8 (56 CP)
5: Telekinesis with ST 10 (70 CP)
6: Telekinesis with ST 12 (84 CP)
7: Telekinesis with ST 15 (105 CP)
8: Telekinesis with ST 17 (119 CP)
9: Telekinesis with ST 19 (133 CP)
10: Telekinesis with ST 21 (147 CP)

This is a bit weaker than the Shadowrun version, which allows you to reach average human strength with Force 3 - but on the other hand, the Shadowrun version is described as somewhat clumsy, and also moves more slowly. So, it seems to even out well.

[Jürgen Hubert]

Originally Posted by Fred Brackin

No, Characters p.62 specifies that Toxic damage never affects Machines. Machines are "physical objects" so Mana Bolt can not be Toxic.

For "generic" damage I think you might be looking for Crushing with No Knockback

Ah, sorry - I meant that a Manabolt can only affect living objects.

[ArchonShiva]

Will roll against drain: Mages maxing out Willpower is a given in SR, so I'm not sure eschewing this will help you maintain the flavour. However, I agree that it's probably not a good idea to simply roll Will to resist drain in this case.

Whatever you do, dissociate Will from IQ and base it on 10. It's a canon optional rule anyway, and it gets you all six Shadowrun attributes as separate entities.

If you really want to stick close to the SR feel, I wouldn't try to make magic look too much like GURPS - it's perfectly in theme that dice work differently when working with supernatural forces. You could keep most of the rolls as per SR and only convert effect to GURPS when the time comes to roll damage or resist. I've done the opposite (using GURPS skills inside Mekton vehicles) and it worked fine.

If you don't want to play outside GURPS, you could take a page from Technical Grappling and don't be afraid to shift magic from roll-under to the damage roll mechanic. Force gives you dice, which you roll and add to attain an effect. A force 4 spell gives you four dice to roll, with your Spellcasting skill adding +1 per die at IQ+2 or whatever. Then make a similar roll for Drain, and pay fatigue based on how much above your Will you rolled.

These aren't complete worked-out examples, but just possible avenues to making magic feel more like its SR self.

Here's one that doesn't conform to my experience of SR magic, but does fit your list of criteria:
Let mages buy cheap Energy Reserves with an accessibility limitation. Use a Will roll for drain, with MoS letting you use some ER and the rest coming from fatigue.

By the way, unlike CrakkerJakk, I think that LoS range for spells (and the absolute requirement to see your target) is actually pretty key to the whole thing.

[benz72]

You could also try a RPM type approach to spell building (with heavy modification)

if you expand greater/lesser concept to other categories you get 'normalized' additive spell cost units.

LoS is one more than Touch, which is one more than Self
Affects insubstantial or armor piercing can be one 'power-up' each
Enhanced damage types (fire/shock) can cost more

This would give a generic spell that, coupled with the force, can determine its cost per whatever mechanics you finally pin down.

[Crakkerjakk]

Originally Posted by ArchonShiva

By the way, unlike CrakkerJakk, I think that LoS range for spells (and the absolute requirement to see your target) is actually pretty key to the whole thing.

I just don't think "there are only these three spell ranges" is key to the flavor of SR. Needing to see your target, sure. That's a different thing though.