Re: GURPS Power-Ups 10: Skill Trees
 

It depends on how flexible you want wizards to be. Having the colleges be the trunk means it will cost a lot of points to be flexible.

Re: GURPS Power-Ups 10: Skill Trees
 

Which is a fair point. I'm more inclined to make the magic trunks between College and All Magic. Like a hypothetical "Elementalist Skill Tree" which has the Air, Earth, Fire and Water colleges, and likely a number of other spells renamed to fit the theme.

Re: GURPS Power-Ups 10: Skill Trees
 

Agreed. As well, Skill Trees also subsume Talents; and Magery is basically a Talent. And that's what your Trunk is: the equivalent of buying levels of Magery.

And whether it's Ritual Magic, RPM, Path/Book Magic, Symbol Magic, Noun/Verb Magic, or Realm Magic, there's a lot of precedent for Colleges/Paths/Realms/etc. to operate on the level of regular skills, as opposed to wildcard skills or Talents — which, again, is where the Trunk operates.

Re: GURPS Power-Ups 10: Skill Trees
 

For my games, I've decided that in addition to replacing mundane talents with Trunks, I'll be letting the Skill Tree structure replace Power Talents (from GURPS Powers). Here's how they are put together in my games.


Trunk = Power Source

A Power Trunk replaces a Power Talent that covers an entire power source that was previously worth [10 x level] (e.g., the Magery advantage is now the Magery Trunk).

Any restriction that applied to purchasing, learning, or improving a Power Talent (e.g., whether it must be purchased as a starting character or not, whether it can be improved, if there are maximum levels, etc.) now apply to the Power Trunk.

Similarly, if the Power Talent provided other limitations to your powers (such as minimum level requirements), count your level in the Power Trunk instead (e.g., instead of spells requiring a minimum level of Magery Power Talent, they now require a minimum level of Magery Trunk.)

Powers that didn't have a [10 x level] Power Talent are not allowed to get a Power Trunk; e.g., if using GURPS Psionic Powers, there is no overarching Psionic Power Talent worth [10 x level], so there therefore isn't any Psionic Trunk.


Branch = Focus

The Branch level now covers a power focus; e.g., fire, telepathy, weather, etc. Or, it represents a Power with a single focus power (e.g. a single Psionic Power like ESP or Telepathy) that as a Power Talent would cost [5 x level]

So, every Magical College is therefore its own Branch (e.g. Fire College, Making and Breaking College, Protection and Warning College, Water College, etc.). Similarly, every Psionic Power is its own Branch (Telepathy, Psychoportation, Psychic Vampirism, etc.) In ritual path magic, every Path is a Branch.

In games with Magical Styles or the equivalent for other powers, you can also get a Branch for the abilities (e.g., spells) of that style, effectively treating it as if it was its own unique focus.

For those that are emulating former Power Talents at [5 x level], just like with Trunks, any rules or restrictions that applied to the Power Talent applies to the Power Branch. So, for the various Psionic ESP or Psionic Telepathy branch, you need to purchase at least 1 level at character creation to be able to learn it, but in game you can increase it as high as you like (to the campaign cap).


Twig = Ability (Skill)

I'm treating the skill required to activate or use a specific ability as a Twig. Therefore, every Spell is a twig, every psionic ability has a Twig for its use, etc. Every specific ritual in Ritual Path Magic is also a Twig.


Leaf = Technique

This is for powers that allow techniques to improve certain aspects of the ability, or to cancel penalties, etc. For example, Psi Techniques from GURPS Psionic Powers.

Since Magery doesn't have these, there are no Leafs in the Magery skill tree.




Difficulty Modifier

Finally, some powers - but not all - will have permanent difficulty modifiers to all skill rolls.

If a power requires the purchase of an underlying advantage for the ability as well as the skill to use it (e.g., Psionic Powers, Chi Elemental Magic powers, a custom powers-based magical system, etc.), then there is no difficulty modifier.

If a power only requires that you purchase a skill to use it (e.g., Magery), then it will include a difficulty modifier. That specific modifier should be designed according to how the power works. E.g., standard GURPS Magic (the skill-based magic system) should impose a -1 per prerequisite spell (what it called Ritual Magic). Incantation Magic (DF19) imposes a penalty based on the amount of "SP" required to build the effect., etc. In a system based on a Modular Abilities, perhaps you impose a -1 penalty per 20 points of the ability being used.

Those difficulty modifiers apply every time you use your power.

So, for example, if the Fireball Spell has a prerequisite count of 4, so it has a difficulty of -4. To cast Fireball, you are rolling against:

(Attribute -5) + Magery + Fire College + Fireball -4


I decided to go for the penalty to powers that are solely skill-based because they are already extremely cheaper to purchase than the power-based advantage + skill build, and the ability to merge all of those individual skills into a single Trunk just made more unfair. Balancing it with a slight penalty every time you use that ability (i.e., cast that spell), in my opinion, makes it more fair.

Re: GURPS Power-Ups 10: Skill Trees
 

Your logic works for magic as powers. But the skill- based magic system presented in the core book has spells that are extremely specific in what they do; every bit as specific as a Technique is.

With that said, there's an added complication when adapting Magic as Powers in this way; and that is that the Powers system is Advantage-based, not Skill-based: what you can do is determined by what Abilities (read: Advantages) that you've purchased; and any involvement of Skills in this arrangement is secondary to that. Skill Trees does nothing to address that.

Re: GURPS Power-Ups 10: Skill Trees
 

Yes obviously, but the text makes an attempt to differentiate between skill trees main and optional rules within skill trees (Fancy Forestry p.20). All I am saying that handling magery is mentioned only within Fancy Forestry and nowhere else. So if I want to use skill trees without extra optional rules, technically there is no guideline for magery.

Re: GURPS Power-Ups 10: Skill Trees
 

I guess I'm not really sure what you're saying. Or more accurately, your statement is understood and correct, but I'm not sure what type of answer you're expecting in the forum. I had assumed you wanted to see what other guidance people here might provide.

Fancy Forestry is clear with their optional rules for handling Magery (specifically under Exotic Species):

Magery could be a Trunk, too, with magical colleges as Branches and spells as Twigs.

That's all you really need. Magery is the Trunk, Single College Magery is the Branch, and Spells are Twigs. Learn your tree accordingly to get your total skill value for any given Spell/Twig. Just using that actually works and is playable as is.

But will that give you the same feel for the magic system? Possibly not. That is why a few of us have posted additional suggestions with respect to providing some additional options (or additional guidance).

Most of us seem to think that a single Magery Trunk letting you cast all spells is too powerful, and thus recommend using the prerequisite count as a modifier (whether all the time or just for spells at default). That comes from the GURPS Magic Ritual Magic option, not Skill Trees.

Dataweaver and myself have raised whether a Spell should be a Twig or Leaf. There's no correct answer here. I can definitely see his point that Spells are very narrow... you are essentially trying to debate if, say Fireball, is narrower than some other Twig like Pistol (a Twig of the Guns Branch)? Probably. That said I personally preferred Twigs for spells, matching Exotic Forestry, but that in no way means they can't be Leaves. I guess for me, the deciding factors is that having spells as Twigs leaves open room to add further techniques that are sub-parts of the spells (which is admittedly absolutely not needed for Spells in magic... but do exist for Psionics, so I'm making psi abilities and spells on equal footing, although having them equivalent is a personal choice, not a rule requirement).

I raised suggestions of whether Magery Trunk actual counts as the Magery Advantage or not for meeting spell prerequisites, which is also something to consider. Why? Because it works the same. Magery gives +1 to all spells. So why not have a Magery Trunk which is effectively +1 to all spells. So you have some optional guidance there. My reason for raising that equivalency was about putting an optional cap on the Magery Trunk that's the same cap as the Magery Advantage (you'll see why below)

I suppose the only area not covered would be guidance as to whether or not getting Magery Trunk really gives you all the hundreds of spell skills, as that Trunk is effectively a skill in all spells. Magery Advantage gives +1 to all known spells, but doesn't give you a default in all spells... you still have to have points in the spell itself. But, on the other hand, Ritual Magic did count as knowing all spells in that college. I'd recommend mirroring that. Therefore, if you only have Magery in the tree structure that leads to a given spell, then it's still considered to be default (no matter how many levels of Magery you have), and you can't cast spells at default. If you have the College Branch or the Spell Twig (or Leaf), then you know the spell and can cast it, including adding Magery to the skill. That's what I would do, anyway. The rules as written in Skill Trees, however, means if you have Magery Trunk, you know all spells. Sure, you're starting at Attribute -5, so that sort of compensates as you won't be very good in all the spells, at least until you raise your Magery very high. At high levels of Magery Trunk, it might problematic in its own way; Magery +15 [105] would give you all spells at the skill cap for the campaign. Whether that's a feature or problem depends on what you want mages to be able to do in your games. (If you think that's a problem, adding Prerequisite Count as automatic penalties helps mitigate that here, as would having a special cap for the Magery Trunk, or the not letting Magery count for actually knowing a spell and only add to known spells.)


If you don't want to convert to a full Skill Tree Structure for Magery (as doing so is clearly optional, as per Fancy Forestry), then the method to bring it on par with other skills in Skill Tree would be continue to use the Magery Advantage as normal, don't have any Trunks for magic, and treat every spell as an independent Branch (which is where skills usually fall when converting between normal skills and Skill Tree). Then it works the same as Magery did before with 1 skill per spell, but is incorporated into the costs of skills in Skill Trees.


Which of these is the correct way? None of them. Even the actual RAW skill-based Magery technically doesn't have a "correct way", since, for example, you can use the Ritual Magic option of a single skill for an entire college with a prereq count penalty. Those come from the existing magic rules. Sure, the "default" way of GURPS Magic is clearly just using skills and not Ritual Magic... but then the "default" Skill Trees recommendation for magic based on Fancy Forestry is also clear: Trunk / Branch / Twig for Magery / College / Spell. Regardless of that, in either one you should still pick magic system the one that works for your game.


Was there anything else not covered that you are specifically looking for guidance with respect to using Skill Trees with Magery?

Honestly, just give it a try in your game, make and play a few mages using Skill Trees, and post your observation and/or further questions here. I'm sure several people can give you their ideas on how they would address any specific questions you may have, and/or appreciate learning from your own observations as to what is or isn't working so they can account for them in their own games. After all, Skill Trees and its ramifications is still new for everyone here.


And if the only point of your original post was just to state "There's no real guidance on magic in Skill Trees", and I just misread that you were seeking more guidance and options, then all I can say to that is "Yeah, that's a fair statement."

Re: GURPS Power-Ups 10: Skill Trees
 

Yes, Malfi is correct. There is very little guidance on how to adapt the standard skill-based magic system to Skill Trees.
Since I value the "mostly done and ready to use" nature of Skill Trees, this is a slight dissapointment.
However, considering word count limits and how much extra work would be neccesary, it's understandable that it was left to the excersize of the reader, or a maybe a future Thaumatology supplement.

Re: GURPS Power-Ups 10: Skill Trees
 

It comes down to the fact that going off on a tangent about magic in a supplement intended to be a genre-independent alternate-GURPS volume limited to "21 pages before the ad. Okay, maybe 22-23 pages before the ad. What, you went to 24 pages? *sigh*" would've been troublesome. I made it very clear in at least three places that this one is for rules-hackers prepared to do some legwork. It is a collection of hyper-optional ideas that the GM may, might, could, is welcome to, and is free to use . . . or not. As the introduction literally states, it's "GURPS Power-Ups 9: Alternate Attributes, but for skills."

Re: GURPS Power-Ups 10: Skill Trees
 

I get it now, many thanks to everyone for clarifying this for me! Especially to Mr. Kromm!