Pinning down Weaving for more consistent rulings

[Mrmdubois]

Eh, Cold Snap is more of a fraying or perfecting spell depending on the kind of environment you're using it on. Either degrading the heat in an area or increasing the cold that's present. Turn Momentum is taking a property than an object already has and giving it a tweak so it doesn't continue in a straight line even though it hasn't hit an obstacle that would redirect it. If you turned the object's kinetic energy into fire, that would be Patterning. It would come to a dead stop and be on fire.

[galivet]

To sum up, here's the clarity I got out of what makes a pretty uncontroversial Weaving spell beyond the explicit constraints from the rule book:

1. Neither the modified property nor the nature of its modification should fall solely under some Arcanum other than the one used for the spell. No to using Matter Weaving alone to modify the velocity of a subject bullet.
2. If the modified property does not fall solely under the Arcanum used for the spell, the spell's subject must belong that Arcanum. Otherwise, the nature of the subject is probably irrelevant. No to using Matter Weaving alone to alter a subject animal's density. Yes to using Forces Weaving alone to modify the color of the light from a subject firefly.

No one discussed the "completely different" piece, but I suppose that so long as the spell only modifies a single property of the subject then there's not a lot of risk there. It's probably just included to properly scope "property" so players err on the side of "change the bird's color" rather than "change the bird's taxonomic genus."

Regarding the examples above, the effects could be achieved in other ways too (e.g. Matter Weaving the air to provide enough resistance to slow down the bullet). And that's the kind of thing I'll be able to suggest to my players with more confidence now to get more thematic use of the various Arcana. Thanks for the insights!

[Scriptorian]

I'll just throw in a couple thoughts.

On Weaving versus Patterning: the way I understand it, they can both be used to edit the same values, but Weaving gives you a slider where Patterning lets you enter a value directly. Like with Life 3 you could modify a human's form, feature by feature, until they resembled an ostrich (it would take a seriously hefty spell, but it's hypothetical possible), whereas Life 4 just lets you replace "human" with ostrich" and bam you're done. Similarly, both Space 3 and Space 4 can be used to change someone's position variable, but Space 4 simply overwrites their location, whereas Space 3 would have to use a cascading spacial distortion field to translate the subject the entire way, requiring higher Potency based on the distance.
Just thought of a shorter way to describe it: Weaving let's you change property "y" by value "x". Pattering let's you change "y" to "x". If that makes any sense.

On which Arcanum to use: I think you can use only Matter to change a living being's density, but Life would be required to keep it functioning normally as a living being. In essence, a solely Matter spell would be dealing bashing damage as it altered the basic properties of the subject's body, which would not be healthy. Conversely, Life by itself could change the subjects biology to a less dense form, but it would be by giving them built-in hydrogen sacks or something. You'd want both Arcana to change the subject's density without strange side-effects.

Also, while you can't directly change a bullet's velocity with Matter, you can do the next-best thing and change it's mass. Conservation of Kinetic Energy (Sleeper science can be useful when you know the rules) dictates that if you magically increase the mass, the velocity will drop. Of course, you'd want to make sure the bullet slows down enough to fall out of the air before it hits you, or it would still hit you just as hard.

[Mrmdubois]

On which Arcanum to use: I think you can use only Matter to change a living being's density, but Life would be required to keep it functioning normally as a living being. In essence, a solely Matter spell would be dealing bashing damage as it altered the basic properties of the subject's body, which would not be healthy. Conversely, Life by itself could change the subjects biology to a less dense form, but it would be by giving them built-in hydrogen sacks or something. You'd want both Arcana to change the subject's density without strange side-effects.

Overall accurate, but this doesn't make a whole lot of sense. You don't use Matter on living subjects, and magic isn't required to come up with compensatory biology to deal with a living being reduced in mass.

[galivet]

Aside from Shrink and Grow, which requires conjunctional Life to work on living beings. It's a weird spell. I would have thought Life 3 would have been enough unto itself if the subject is living.

After beating my head against fundamentally the same kinds of issues with the game rules from several different angles, at this point I just accept that the rule book is not a technical manual on magic. From a game world perspective, mages are probably just as befuddled about the inconsistencies and weird exceptions in how it works as we are. The Practices are the best taxonomy mages can come up with for spell effects, but experienced mages know that they're, to quote a pirate, more what you would call guidelines than actual rules. That leaves the ST with a lot of latitude in adjudicating spells as well as opportunities to build mysteries around spells that don't color within the lines.

What finally broke me was when I noticed that Teleportation isn't mentioned as Lasting and I couldn't find any solid rule-based criteria for it being so***. Fuck it, of course it's Lasting, if some mage doesn't like it they can take an Obsession for figuring out why it works the way it does and I'll make up a reason for it as best I can.

*** Suppose you take the transformation of a person-sized area of space into a different person-sized area of space (in a different spot) as the primary effect of the spell, and the secondary effect is that the person occupying that space moves to the new location. Then the secondary effect is Lasting by the usual convention -- cool. However when the duration of the spell ends, the person better have moved out of that spot, or they're getting teleported back where they started as the primary effect reverses itself to normal. Or possibly just part of their left leg gets teleported back if they were in the process of moving when the spell's duration expires. It's a can of worms. I'm just going to say it's Lasting because it's obvious it's meant to be and it'll be far from the first published spell that doesn't perfectly jive with the general rules.

Of course the spell text includes verbiage such as "summon a subject to her from anywhere in the world" which makes it seem like the person getting teleported is the subject of the spell. In that case, rewriting the person's location is the primary effect. Don't care; it's still Lasting.

[galivet]

Also, while you can't directly change a bullet's velocity with Matter, you can do the next-best thing and change it's mass. Conservation of Kinetic Energy (Sleeper science can be useful when you know the rules) dictates that if you magically increase the mass, the velocity will drop. Of course, you'd want to make sure the bullet slows down enough to fall out of the air before it hits you, or it would still hit you just as hard.

Yeah I'm pretty sure that with sufficient knowledge of physics a smart person can come up with a 3-dot Matter spell to more or less duplicate the in-game effect of almost any Forces spell of 4 dots or lower. Matter has the ultimate Many Roads overlap with Forces when the subject is an inanimate object. Trying to come up with an example of a Forces-aligned property of an object that could not somehow be altered using Matter Weaving proved to be an impossible exercise for me; I just did my best to get the point across.

[Mrmdubois]

Some things don't get mentioned as being Lasting because it's just obvious that it is. Teleporting is one of those, Shaping is another, and there are more.

The example of Shrink and Grow is one of those things where I go, they should have put an And/Or in there for the Life bit. I'm more than happy to treat the example spells as guidelines rather than hard rules. The writers were essentially doing exactly what we do when we do creative thaumaturgy, and not all of their decisions will make perfect sense in retrospect.

[proindrakenzol]

On which Arcanum to use: I think you can use only Matter to change a living being's density, but Life would be required to keep it functioning normally as a living being. In essence, a solely Matter spell would be dealing bashing damage as it altered the basic properties of the subject's body, which would not be healthy. Conversely, Life by itself could change the subjects biology to a less dense form, but it would be by giving them built-in hydrogen sacks or something. You'd want both Arcana to change the subject's density without strange side-effects.

Matter cannot affect living beings at all.

Also, while you can't directly change a bullet's velocity with Matter, you can do the next-best thing and change it's mass. Conservation of Kinetic Energy (Sleeper science can be useful when you know the rules) dictates that if you magically increase the mass, the velocity will drop. Of course, you'd want to make sure the bullet slows down enough to fall out of the air before it hits you, or it would still hit you just as hard.

There is no conservation of kinetic energy, and conservation of momentum requires there to not be magic. Reducing an object's mass with Matter would not alter its velocity, it would alter its total momentum (p = mv). What you could do with Matter is alter the object's shape to an anti-aerodynamic one, causing it to slow due to increased drag.