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Hi,

There're a few ways to "halve a units movement characteristic", including (but not limited to) the Space Marine Tremor Shell strat, the Vigilus Suppressive Fire strat, the Tenebrous Curse psychic power, etc...

Would those effects stack (e.g. movement characteristic is halved, and then the already halved characteristic is halved again), or is the effect always calculated from the "base" movement characteristic and thus would not stack?


Cheers,

Sunny Side Up wrote:
Hi,

There're a few ways to "halve a units movement characteristic", including (but not limited to) the Space Marine Tremor Shell strat, the Vigilus Suppressive Fire strat, the Tenebrous Curse psychic power, etc...

Would those effects stack (e.g. movement characteristic is halved, and then the already halved characteristic is halved again), or is the effect always calculated from the "base" movement characteristic and thus would not stack?


Cheers,

As with everything in 8th edition, it depends on the actual rule in question.

As far as I can tell, however, for the examples you listed (along with Doombolt) simply state that they "halve(s) their Move characteristic" without any qualifiers. Thus, as per page 175 of the BRB:

BRB Page 175 wrote:You may also encounter abilities and rules that modify a characteristic. All modifiers are cumulative, though you should apply any multiplication or division to the characteristic (rounding fractions up) before applying any addition or subtraction.

Emphasis mine. So while they do stack, it now comes down to what exactly "modifiers are cumulative" means. Does it mean 1) "Apply each modifier in turn using the result to feed the subsequent modifier" or does it mean 2) "combine all the modifiers together first and then apply that modifier"?

FWIW I think it's the latter, you combine all the modifiers and then apply them and FWIW I don't think there is a situation where doing it either way actually changes the result since you always round fractions up.

Agree with BCB.

While there is no RAW to guide how to put it together, due to always rounding up it's actually mathematically impossible for it to make a difference.

Well, if it's cumulative, it would still have a difference, rounding or not.

A unit of Genestealers (movement 8) is hit by tenebrous curse in the psychic phase, halving their movement to 4.

The same unit of Genestealers is hit by suppressive fire in the shooting phase, cumulatively halving their movement to 2 (?)

Sunny Side Up wrote:
Well, if it's cumulative, it would still have a difference, rounding or not.

A unit of Genestealers (movement 8) is hit by tenebrous curse in the psychic phase, halving their movement to 4.

The same unit of Genestealers is hit by suppressive fire in the shooting phase, cumulatively halving their movement to 2 (?)

What I/we meant by "make a difference" is that whether you halve, round then halve again; or quarter then round it will always end in the same result as you are always rounding up, not rounding to nearest. Likewise if you're halving in different phases.

 BaconCatBug wrote:

Sunny Side Up wrote:
Well, if it's cumulative, it would still have a difference, rounding or not.

A unit of Genestealers (movement 8) is hit by tenebrous curse in the psychic phase, halving their movement to 4.

The same unit of Genestealers is hit by suppressive fire in the shooting phase, cumulatively halving their movement to 2 (?)

What I/we meant by "make a difference" is that whether you halve, round then halve again; or quarter then round it will always end in the same result as you are always rounding up, not rounding to nearest. Likewise if you're halving in different phases.

Yes, this is what I'm saying.

Say a model has a Move of 9" and it gets halved twice.

Apply all at once:
1/4 of 9 is 2.25, rounded to 3 (because unlike normal maths, 40k always rounds up)

Apply in stages:
1/2 of 9 is 4.5, rounded to 5. Half of 5 is 2.5, rounded to 3.

Same result.