Speed modifier dependant on direction?

SciFiNut · 10-23-2012, 12:28 AM

On p550 of "Basic Set - Campaigns" there is an example of someone shooting at a motorcyclist 40 yards away travelling at 30 yards/second (60 mph). Does anyone rule that the speed modifier depends on the relative direction in which the target is moving?

for a 30 yards/sec motorcyclist, I would play it like this.

If moving directly towards/away from shooter, ignore speed.
If moving diagonally across shooter's line of sight, add half speed to range.
If moving perpendicularly across the shooter's line of sight, add full speed to range.

The above would give -9 only if the biker was traveling perpendicularly or diagonally across the shooter's line of sight, otherwise -8. At closer ranges one would see greater variation in the effect of speed and direction on the modifier (as the table becomes more "granular" closer to the 0 modifier).

Maz · 10-23-2012, 04:34 AM

Quote:

Originally Posted by SciFiNut

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If moving directly towards/away from shooter, ignore speed.
If moving diagonally across shooter's line of sight, add half speed to range.
If moving perpendicularly across the shooter's line of sight, add full speed to range.

This is what I play with as well.

Bruno · 10-23-2012, 08:23 AM

We've got engineers in our group, and have been known to calculate the relative lateral velocity straight up, via a little trig.

So yes sort of, but we've gone overboard. :P

Normally it's more like your "rule of thumb" though.

gilbertocarlos · 10-23-2012, 03:08 PM

Quote:

Originally Posted by Bruno

We've got engineers in our group, and have been known to calculate the relative lateral velocity straight up, via a little trig.

For those who want to know how, simply multiply by the cos with the line straight up to you.

Anaraxes · 10-23-2012, 03:56 PM

The simplification assumes that the weapon's trajectory is close to flat and that time-of-flight to the target is very short. For a rifle shooting at a motorcycle, perhaps. But with a weapon that has an arc, such as a bow at range, or a mortar, then movement directly away does affect where you have to aim to hit the target when the projectile lands.

10-23-2012, 12:28 AM	#1
SciFiNut Join Date: Dec 2011	Speed modifier dependant on direction? On p550 of "Basic Set - Campaigns" there is an example of someone shooting at a motorcyclist 40 yards away travelling at 30 yards/second (60 mph). Does anyone rule that the speed modifier depends on the relative direction in which the target is moving? for a 30 yards/sec motorcyclist, I would play it like this. If moving directly towards/away from shooter, ignore speed. If moving diagonally across shooter's line of sight, add half speed to range. If moving perpendicularly across the shooter's line of sight, add full speed to range. The above would give -9 only if the biker was traveling perpendicularly or diagonally across the shooter's line of sight, otherwise -8. At closer ranges one would see greater variation in the effect of speed and direction on the modifier (as the table becomes more "granular" closer to the 0 modifier). Last edited by SciFiNut; 10-23-2012 at 12:32 AM.

10-23-2012, 08:23 AM	#3
Bruno Join Date: Sep 2004 Location: Canada	Re: Speed modifier dependant on direction? We've got engineers in our group, and have been known to calculate the relative lateral velocity straight up, via a little trig. So yes sort of, but we've gone overboard. :P Normally it's more like your "rule of thumb" though. __________________ All about Size Modifier; Unified Hit Location Table A Wiki for my F2F Group A neglected GURPS blog

10-23-2012, 03:56 PM	#5
Anaraxes Join Date: Sep 2007	Re: Speed modifier dependant on direction? The simplification assumes that the weapon's trajectory is close to flat and that time-of-flight to the target is very short. For a rifle shooting at a motorcycle, perhaps. But with a weapon that has an arc, such as a bow at range, or a mortar, then movement directly away does affect where you have to aim to hit the target when the projectile lands.