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Old 09-06-2013, 11:25 PM   #1
talus
 
Join Date: Sep 2011
Default Magic spell prerequisite count corrections

I've recently been looking at adjusting the prereq counts for a ritual mage in my campaign, so of course I started by writing a script to parse each spell's prerequisites from GURPS Magic and then calculate the minimum number of prerequisites according to the method used in Thaumatology (advantages count as 0). This of course exploded into a multi-week project, but now I'm finally done :).

Out of 837 spells, 33 didn't match my script's results. They fall into three general categories: probable textual errors, 'x different colleges' interpretation (Wish/Great Wish), and apparent bad counts. I manually analyzed most of the differences to verify my script's counts, though I didn't dive into the really big ones (they are left as an exercise for those even more obsessive than I).

I'd like to get some feedback on the differences and some spot-checking on my data. Hopefully this can be put into an errata eventually. Below is my analysis, and I've attached a spreadsheet with the full list of spells and counts from both Thaumatology and my script as well as the calculated list of requirements for each spell (though those are a bit hard to read).

Also, I reviewed the errata @ http://www.sjgames.com/errata/gurps/4e/magic_2.html. If there's additional data elsewhere please point me to it!

Results Spreadsheet (xls/csv):
http://www.dsmall.com/gurps_files/CalcedPrereqsCSV.zip
http://www.dsmall.com/gurps_files/CalcedPrereqsXLS.zip

Out of 837 spells: Found 33 different spells with a total prereq delta of 63.

Summary:

Probable Errata:
  • Homunculus
  • Timeslip Other (VH)
  • Crystal Ball (also calculation error) 13 -> 16 or 8
  • Create Gate (VH)
'x different colleges' related
  • Great Wish (VH) 18 -> 17
  • Wish (VH) 17 -> 16
Apparent Bad Counts:
  • Analyze Magic 3 -> 2
  • Animate Object (VH) 6 -> 5
  • Astral Block 16 -> 15
  • Body of Shadow (VH) 4 -> 7
  • Duplicate (VH) 15 -> 14
  • Effigy (VH) 13 -> 12
  • Essential Acid (VH) 13 -> 15
  • Forest Warning 4 -> 1
  • Geyser (VH) 9 -> 11
  • Hideaway 15 -> 18
  • Inscribe 7 -> 6
  • Know True Shape 9 -> 7
  • Leak 16 -> 19
  • Mapmaker 9 -> 8
  • Remove Curse 13 -> 15
  • Rebuild/TL (VH) 22 -> 23
  • Recall 9 -> 8
  • Repel Spirits 14 -> 12
  • Schematic/TL (VH) 7 -> 6
  • Suspend Mana (VH) 11 -> 12
Unanalyzed, likely calculation errors:
  • Corpulence (VH) 16 -> 18
  • Doppelgänger (VH) 29 -> 31
  • Enslave (VH) 14 -> 15
  • Hide Object 20 -> 19
  • Move Terrain (VH) 29 -> 27
  • Sanctuary (VH) 21 -> 19
  • Wraith (VH) 24 -> 25

Details:

Probable Errata:
-----------------------------
Homunculus : (15->5) "Magery 2 and Mind-Sending."
Probably a typo in the prereq string: should it also require Enchant? If so, then the count is correct.

Timeslip Other (VH): (7->6) "Timeport."
Probably a typo in the prereq string: Timeport has 5 prereqs, Timeslip has 6. If it depends on Timeslip then the count is correct.

Crystal Ball : (13-> 16 or 8) "Divination (Crystal-Gazing)."
Possible typo- may also want Enchant (VH). Count off in both cases.
Code:
: Enchant (VH) -> [10 college spells]
: Divination (Crystal-Gazing) -> History -> Trace -> Seeker -> [2 "seek"]
:                                                           -> Seek Machine/TL, Seek Earth
:                             -> Earth Vision -> Shape Earth -> [seek earth]
: [10 college spells] has [History, Seek Earth, Seek Machine/TL] +7 other spells
: calc: 16, or if no Enchant then 8
Create Gate (VH) : (14 -> 13?) "Control Gate. The caster must also know Teleport to create a gate leading to another place, Timeport to create a gate leading to another time, or Plane Shift to create a gate leading to another plane of existence."
This is a single spell, not 3 variants, and Teleport/Timeport/Plane Shift are listed as enabling specific functionality rather than as actual requirements. The wording indicates you can technically learn the spell without any of those, though it would be of very limited use.


'x different colleges'
-----------------------------
This appears to be somewhat inconsistently interpreted. I see three ways of interpreting the variously worded statements:
1) Exclude colleges of any top-level prereqs: Ex. "Lesser Wish and at least one spell in each of 15 different colleges." would exclude all Enchant College spells. This interpretation would change many of the counts from RAW. Also, for Body of Wind, that case is explicitly called out: "Magery 3; Body of Air and Windstorm at 16+ each; and one spell from each of five different colleges besides Air.". Therefore I assume that this is not a correct general interpretation.
2) Exclude only named top-level prereqs: In the example, Lesser Wish (VH) would not be included in the 15 different colleges, but the prereq to Lesser Wish (VH), Enchant (VH), would. This seems to be the most commonly followed (though not for that particular example).
3) Allow top-level prereqs. Ex: Seek Gate: "Magery 2, Seek Magic, and one spell from each of 10 colleges." would only have 10 prereqs, since Seek Magic could count in the 10. This breaks several counts, and doesn't seem to be the designer's intention.

I have assumed that option '2' is correct in my calculations, regardless of minor wording variations. Only Wish (VH) & Great Wish (VH) did not match:

Wish (VH) : (17 -> 16) "Lesser Wish and at least one spell in each of 15 different colleges."
Prereq tree is: Lesser Wish (VH) -> Enchant (VH) -> [10 different colleges]
Enchant (VH) should be included in the 15 different colleges requirement

Great Wish (VH) : (18 -> 17) "Magery 3, Wish, and a combined DX and IQ of 30+."
Adjust as per Wish (VH), above, to 17
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Old 09-06-2013, 11:25 PM   #2
talus
 
Join Date: Sep 2011
Default Re: Magic spell prerequisite count corrections

Apparent Bad Counts
---------------------
Analyze Magic : (3 -> 2) "Identify Spell."
Code:
: Identify Spell -> Detect Magic
: calc: 2
Animate Object (VH) : (6 -> 5) "Magery 2 and at least three "Shape" spells."
Code:
: Pick: Shape Fire, Shape Metal, Shape Earth
: Shape Fire -> Ignite Fire
: Shape Metal -> Shape Earth -> Seek Earth
: [shape earth]
: calc: 5
Astral Block : (16 -> 15) Summon Spirit and Repel Spirits.
Code:
: Summon Spirit -> Death Vision
: Repel Spirits -> Banish -> [spells from 10 colleges]
:               -> Turn Spirit -> Fear -> [empathy advantage]
:                              -> Sense Spirit -> [death vision]
: [spells from 10 colleges] [fear, turn spirit] + 8 more
: calc: 15
Body of Shadow (VH): (4 -> 7) "Magery 2, Shape Darkness, and at least three Movement spells."
Shape Darkness has 3 Light/Dark prereqs, plus 3 movement = 7, not 4

Duplicate (VH) : (15 -> 14) "Create Object and Copy."
Code:
: Create Object -> Create Earth -> Earth to Stone -> Shape Earth -> Seek Earth
:               -> Perfect Illusion -> Complex Illusion -> Sound
:                                                       -> Simple Illusion
: Copy -> Dye -> Restore -> [simple illusion]
:             -> Colors -> Light
: calc: 14
Effigy (VH) : (13 -> 12) "Magery 2, Enchant, Scryguard, and Ward."
Scryguard and ward are both in Meta college, so only one counts against Enchant's 10 college req. 11 for Enchant (includes Scryguard), 1 for Ward = 12 total.

Essential Acid (VH): (13 -> 15) "Magery 3 and all six Acid spells."
Code:
: Acid Ball -> Create Acid -> Create Water -> Purify Water -> Seek Water
:                          -> Create Earth -> Earth to Stone -> Shape Earth -> Seek Earth
: Spit Acid (VH) -> Acid Jet -> Water Jet -> Shape Water -> [create water]...
:                -> Resist Acid -> [create acid]...
: Rain of Acid -> [create water, create earth]...
: [acid jet, resist acid, create acid]...
: calc: 15
Forest Warning : (4 -> 1) "Sense Danger or four plant spells."
RAW prereq calcs assume advantages (ex. Sense Danger has 0 prereq count).
Code:
: Sense Danger -> [danger sense advantage]
Geyser (VH): (9 -> 11) "Six Water spells, including Create Spring, and either four Earth spells or four Fire spells."
Create spring has 6 water and 2 earth prereqs. Geyser therefore has 7 water and 2 earth, +2 earth => 11

Hideaway : (15 -> 18) "Enchant, Create Object, and Lighten."
Create Object (VH) has 8 prereqs- 4 Earth, 1 Sound, and 3 Illusion and Creation. Lighten has only Enchant
So 4 Earth + 1 Sound + 4 Illusion and Creation + Lighten + Enchant + 'at least 1 spell from 10 other colleges'
calc: 4 + 1 + 4 + 1 + 1 + 1*7 = 18

Inscribe : (7 -> 6) "Simple Illusion and Copy."
Code:
: Simple Illusion -> [iq 11, can see]
: Copy -> Dye -> Restore -> [simple illusion]
:             -> Colors -> Light
: calc: 6
Know True Shape : (9 -> 7) "Magery 1, any one shifting spell (Shapeshifting, Alter Visage or Body, Plant Form, Shrink, etc.), and either Aura or Know Illusion."
Code:
: Shapeshifting (VH) -> [6 other spells]
: Aura -> Detect Magic
: calc: 7
Leak : (16 -> 19) "Hideaway."
Hideaway (above) has 18 (not 15), so Leak has 19, not 16.

Mapmaker : (9 -> 8) "Inscribe and Measurement."
Adjust per Inscribe, above: calc: 8

Remove Curse : (13 -> 15) "Magery 2 and at least one spell from each of 15 different colleges."
Likely typo. calc: 15.

Rebuild/TL (VH) : (22-> 23) "Magery 3, Repair, Create Object, and at least three spells of each element."
Code:
: Repair -> Rejoin -> Weaken -> Find Weakness -> (1 each element)
:                  -> Restore -> [find weakness]...(or [simple illusion] selected below, doesn't matter)
: Create Object -> Create Earth -> Earth to Stone -> Shape Earth -> Seek Earth
:               -> Perfect Illusion -> Complex Illusion -> Sound
:                                                       -> Simple Illusion
: 14 so far, with > 3 earth. So +9 for Water/Fire/Air = 23
: calc: 23
Recall : (9 -> 8) "Magery 2, Memorize, and History."
Code:
: Memorize -> [6 knowledge spells] 
: History -> Trace -> Seeker -> [2 seek]
:                            -> Seek Magic -> Detect Magic
:                            -> Seek Plant
: [history, trace, seeker, seek magic, detect magic] are all Knowledge, so only need 1 more spell for 6 Knowledge req.
: calc: 8
Repel Spirits : (14 -> 12) "Banish and Turn Spirit."
Code:
: Banish -> [spells from 10 colleges]
: Turn Spirits -> Fear -> [empathy advantage]
:              -> Sense Spirit -> Sense Life
: [spells from 10 colleges][fear, sense spirit, sense life] +7 more
: calc: 12
Schematic/TL (VH) : (7 -> 6) "Reveal Function and History."
Code:
: Reveal Function/TL -> Seek Machine/TL 
: History -> Trace -> Seeker -> [2 seek spells]
:                            -> [seek machine/tl]
:                            -> Seek Plant 
: calc: 6
Suspend Mana (VH) : (11 -> 12) "Suspend Magic and spells from at least 10 different colleges."
Code:
: Suspend Magic -> Suspend Spell -> Counterspell (all Meta school) 
: [10 different colleges] +9 spells
: [8 other spells: don't care]
: calc: 12
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Old 09-07-2013, 12:59 AM   #3
SCAR
 
Join Date: Oct 2004
Location: Yorkshire, UK
Default Re: Magic spell prerequisite count corrections

Thaumatology has an updated Prerequisite Count, and some notes on the count.
Magic page 200 also says to add 1 for every full 10 points of required advantages, including Magery - which explains Analyze Magic, which requires 2 spells and Magery 1 for the extra +1, giving the listed result 3!
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Old 09-07-2013, 05:17 AM   #4
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Default Re: Magic spell prerequisite count corrections

Back in the Thaumatology play test I was asked by the lead play tester to do the analysis to correct those numbers. I have to say, if you want a good strong headache and some blurry vision, go through every single spell in the Magic book and recount them.

I had a set of spreadsheets I sent in to show the calculations... it was a lot of work. I mean a *lot* of work counting, recounting, checking, and double checking all of the counts. I cannot recall if any of my work ended up being the basis for the updated counted in Thaumatology, bt I think the numbers that ended up in it are pretty good.
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Old 09-07-2013, 09:20 AM   #5
talus
 
Join Date: Sep 2011
Default Re: Magic spell prerequisite count corrections

Yikes! I can't imagine taking on this task manually. Even with a script I had more than a few headaches, and with a spreadsheet...

Also, I guess it isn't clear in my thesis, but the counts I'm comparing against are from Thaumatology.
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Old 09-07-2013, 10:54 AM   #6
Fred Brackin
 
Join Date: Aug 2007
Default Re: Magic spell prerequisite count corrections

Quote:
Originally Posted by talus View Post
Probable Errata:
-----------------------------
Homunculus : (15->5) "Magery 2 and Mind-Sending."
Probably a typo in the prereq string: should it also require Enchant? If so, then the count is correct.


Crystal Ball : (13-> 16 or 8) "Divination (Crystal-Gazing)."
Possible typo- may also want Enchant (VH). Count off in both cases.
Code:
: Enchant (VH) -> [10 college spells]
: Divination (Crystal-Gazing) -> History -> Trace -> Seeker -> [2 "seek"]
:                                                           -> Seek Machine/TL, Seek Earth
:                             -> Earth Vision -> Shape Earth -> [seek earth]
: [10 college spells] has [History, Seek Earth, Seek Machine/TL] +7 other spells
: calc: 16, or if no Enchant then 8
Homunculus is an Enchantment Spell. All Spells of the Enchantment College except for Enchant and Scroll have Enchant as a preprequisite.

If I understand what you're asking the above applies to the Crystal Ball Enchantment as well.

I hope you will forgive me for not diving deeper into your project but in personal opinion prerequisite counts are evil and I will never use any form of magic that requires their calculation. :)
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Old 09-07-2013, 11:42 AM   #7
talus
 
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Default Re: Magic spell prerequisite count corrections

I certainly understand that opinion :). The reason this whole project started is that Ritual Magery basically excludes whole swathes of spells with little justification (esp. Meta/Enchantment), and I wanted to be able to re-calculate the count with different methods to get a more balanced difficulty curve for those spells.
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Old 09-07-2013, 01:18 PM   #8
jeff_wilson
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Default Re: Magic spell prerequisite count corrections

Quote:
Originally Posted by talus View Post
Yikes! I can't imagine taking on this task manually. Even with a script I had more than a few headaches, and with a spreadsheet...
Yeah, that guy was a slave driver.
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Old 09-07-2013, 06:25 PM   #9
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Default Re: Magic spell prerequisite count corrections

Quote:
Originally Posted by jeff_wilson View Post
Yeah, that guy was a slave driver.
Nah. Great guy, actually. I had a great time working on that play test. :)
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