Steve Jackson Games Forums Distance for Hearing/Vision rolls?
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 01-05-2023, 11:42 AM #1 thom   Join Date: Oct 2011 Distance for Hearing/Vision rolls? OK, in my Fantasy campaign, I've got a Hearing/Vision contest coming up in my next session, and I want to do it right. Situation: PC on night watch for a caravan, and a 10-man group of orcs (with Night Vision 5) is heading towards the PC for an attack. • the Orcs are not using stealth; they're moving at Speed of 4. • I'm figuring this gives a +2 on hearing them, accounting for the size of the group. • It's a cloudy night, so -4 to the PC's Vision rolls. • the PC is standing behind a torch, and doesn't have any Night Vision (I'm expecting they'll learn from this mistake-assuming they survive ) With a Perception of 12, and +2 for hearing based on group size, and -4 for a cloudy night; IF the PC rolls a '12' HOW FAR AWAY does he see or hear the orcs?? thom
 01-05-2023, 12:15 PM #2 Varyon   Join Date: Jun 2013 Re: Distance for Hearing/Vision rolls? If he's standing behind the torch, his night vision is nonexistent. The torch itself, based on the "Illumination Levels Table" from Powers: Enhanced Senses*, produces light that gives a -1 to see at 1 yard away, and a further -1 per +2 SSR to Range - -2 at 2 yards, -3 at 5 yards, and -4 at 10 yards, at which point there's no difference between the light from the torch and the ambient light (which is also -4)... but I'd apply a -2 beyond that 10 yards, on account of the character has non-adapted night vision (because he's staring at a torch). The orcs are in plain sight, for +10 to see them, and a net +4 (not counting Range) if further than 10 yards away, net +6 if further than 5 yards away, net +7 if further than 2 yards away. For a roll of 12 to succeed, the character's effective Sight needs to be 12; net +4 would negate -4 for Range, which conveniently is 10 yards away. So they'd be spotted around 10 yards away - unless you decide to treat them as easier to see due to the size of the group; 10 orcs could potentially be justified as being up to SM+4 (10x the size of a typical orc) if they're all walking side-by-side; I'd call them SM+2 instead, in which case they'd be spotted around 20 yards away. In terms of noise, I don't currently have access to the Hearing Table (from High Tech as well as Powers: Enhanced Senses), but a bit of searching online indicates a "normal conversation" (which further searching puts around 60 dB) can be heard at 1 yard with a roll against Hearing+0, and I know it's +2 SSR to Range or -10 dB per -1 to Hearing. If the orcs are talking, then if they're all talking things might rise to around 5x as loud as that "normal conversation," which is around +25 dB - +2 to Hearing at 1 yard. Most likely they aren't that loud, but let's go with that. At +2 to Hear at 1 yard, and -1 per +2 SSR to Range, a roll of 12 for a character with Hearing 12 would result in them being detected at 5 yards away. So, they'd be seen before they are heard, if I'm remembering the Hearing rules correctly (if you haven't received other responses by then, I'll try to remember to check my books when I get home and give you an update), and would probably be seen at around 20 yards away. Note they'll see the caravan much sooner than that, as that torch will be visible from a long ways off. *EDIT: There's some language in the table about having a light source in a dark area rendering you unable to see outside of the illuminated area at all, but without further guidelines, I don't really know how to use that, so I'm ignoring it here. EDIT2: Considering the character is making the rookie mistake of having the torch in front of him while on watch, does he happen to have any relevant skills such as Soldier? If so, I'd be inclined to allow an IQ-based roll for the character to realize that's not a good idea. __________________ GURPS Overhaul Last edited by Varyon; 01-05-2023 at 12:25 PM.
01-05-2023, 03:31 PM   #3
thom

Join Date: Oct 2011
Re: Distance for Hearing/Vision rolls?

Quote:
 Originally Posted by Varyon If he's standing behind the torch, his night vision is nonexistent.... *EDIT: There's some language in the table about having a light source in a dark area rendering you unable to see outside of the illuminated area at all, but without further guidelines, I don't really know how to use that, so I'm ignoring it here. EDIT2: Considering the character is making the rookie mistake of having the torch in front of him while on watch, does he happen to have any relevant skills such as Soldier? If so, I'd be inclined to allow an IQ-based roll for the character to realize that's not a good idea.
OK, so let's put him 2 yards to one side of the torch - how does that improve things? I kinda figured spotting the orcs is gonna be more likely than hearing them - especially without any hearing advantage...

 01-05-2023, 04:53 PM #4 Varyon   Join Date: Jun 2013 Re: Distance for Hearing/Vision rolls? At my books now, looks like my only error there was that I forgot Hearing ranges don't follow SSR, but are true doublings. Turns out that even if they aren't talking, someone who isn't trying to be stealthy would probably be around 60 dB, as the table in Loudness Levels (P:ES21) notes this is where a failed Stealth roll would be. If we treat it as around 80 dB for there being a group (equivalent to a loud conversation; note 90 dB is for a shout, and that's probably too loud for just ten orcs walking), it's an unmodified Hearing roll at 4 yards. For vision, there actually aren't any rules related to where the light source is at (I was misremembering, and going off of a playtest-formatted version of the Illumination Table - from when we were discussing errata on the forums - which wasn't quite as readable as the publication-formatted version in Powers: Enhanced Senses), so it being behind you, in front of you, to the side, etc, doesn't matter. The text states the +10 for Plain Sight only applies within the illuminated area, and that you're at -7 to see anything outside of it... but doesn't define what the illuminated area is. Is it the area where the light source makes a difference? That seems rather excessive - a 120W lightbulb (+0) being on within your line of sight during Sunset (-1) certainly shouldn't make everything more than a yard away from that lightbulb be at -7 to see! Is it everything the light reaches? The light reaches everything if there isn't something in the way (in fact, going off of the Illumination Table, the only way to actually have a -10 to see is if you're in an area that is completely enclosed by light-blocking barriers). Without clarification, I'm going to ignore that rule. So, ultimately, I think that the -2 I assumed beyond 10 yards shouldn't be in play. Again, light levels with a torch are at -1 at 1 yard, -2 at 2 yards, -3 at 5 yards, and -4 beyond that. Orcs who aren't sneaking should count as in plain sight, for +10 to see them, so beyond 5 yards we're at a net +6 to Vision, ignoring Range. This means a roll of 12 for a character with Vision 12 will spot an orc at 20 yards away. If we give the orcs an effective +2 to SM for there being 10 of them, they'll be spotted 50 yards away. __________________ GURPS Overhaul
 01-05-2023, 05:48 PM #5 whswhs   Join Date: Jun 2005 Location: Lawrence, KS Re: Distance for Hearing/Vision rolls? I think the question is, not "are you within the circle it illuminates?" but "are you looking at the light source?" If that light source is within your field of vision, your eyes will adapt to it, and thus be handicapped in seeing things that are darker. __________________ Bill Stoddard I don't think we're in Oz any more.
01-05-2023, 08:10 PM   #6
Varyon

Join Date: Jun 2013
Re: Distance for Hearing/Vision rolls?

Quote:
 Originally Posted by whswhs I think the question is, not "are you within the circle it illuminates?" but "are you looking at the light source?" If that light source is within your field of vision, your eyes will adapt to it, and thus be handicapped in seeing things that are darker.
Are you saying the rule from Powers: Enhanced Senses is meant to be something like "You are at +10 to see the light source, as it counts as In Plain Sight, but are at -7 to see anything else, in addition to any darkness penalties"? That still runs into the "lightbulb at sunset" issue. Or would you need to be close enough to the light source that you are more visible than you would be with ambient light alone for this to come into play - I could certainly buy that having a 120W lightbulb only a yard from your face blinds you to everything else.
EDIT: On second thought, that doesn't quite work either - a quick bit of reality checking shows me that I can still see things elsewhere in my room even when looking directly at the computer monitor, which is by far the brightest thing here (when it goes off, the only notable source of light is the dimly-glowing LED on my PC). Certainly I can see things in my room better when just using the light of the monitor rather than looking directly at it, but I wouldn't say by any more than would be covered by the -2 for my eyes not being appropriately adjusted.
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GURPS Overhaul

Last edited by Varyon; 01-05-2023 at 08:15 PM.

 01-06-2023, 10:15 AM #7 thom   Join Date: Oct 2011 Re: Distance for Hearing/Vision rolls? OK, lemme see if I'm reasonably close to understanding this: 1] the PC has a Perception of 12 and he's not looking "into the light source" 2] add +10 for "in plain sight" since the orcs are not using Stealth while Moving at 4 hexes/second, and (let's say) +2 for group size, which gives us a Vision roll of 24 3] then we have -4 for cloudy night, when the PC is looking beyond the 6-hex range of the torch; so the Vision roll is now 20 4] with a roll of '12' that's 8 under, and checking the Speed/Range chart that means the PC sees the orcs at 50 yards?? Is that correct? thom Last edited by thom; 01-06-2023 at 12:06 PM.
01-06-2023, 02:37 PM   #8
Pursuivant

Join Date: Apr 2005
Re: Distance for Hearing/Vision rolls?

Quote:
 Originally Posted by thom 2] add +10 for "in plain sight" since the orcs are not using Stealth while Moving at 4 hexes/second, and (let's say) +2 for group size, which gives us a Vision roll of 24
If you're using books other than Basic Set, there are further Vision modifiers for camouflaged or highly visible clothing. Penalties to Vision apply if there is Concealment between the observer and the thing they're trying to see. Bonuses might apply to Hearing if the orcs are moving in ordinary armor (+1 to +4 depending on armor type & movement speed). Maybe add +1 or +2 based on the size of the group if they're all moving as a unit.

Quote:
 Originally Posted by thom 3] then we have -4 for cloudy night, when the PC is looking beyond the 6-hex range of the torch; so the Vision roll is now 20
Cloudy night in areas without light pollution would have a Darkness Penalty of -5 to -9 depending on moon phase/brightness and cloud cover.

Quote:
 Originally Posted by thom Is that correct? thom
Per GURPS Basic Set rules, you're correct for Vision rolls. Hearing rolls use a different range progression, per B358.

Traits like Parabolic Hearing and Telescopic Vision effectively reduce range from the "detector" to the thing they're trying to detect, reducing Range penalties.

Don't forget Comprehension rolls for sentries to interpret what they're seeing. ("You see something moving in the darkness" vs. "You see armed figures moving in the darkness.")

Muddying the Waters

Various house rules and old rules concepts.

Unknown Contacts: GURPS 3E had the concept of "No Contact, Contact, Identification, Detailed Identification" for sensors, including Vision rolls (AKA "The Mk 1 Eyeball"). Success only gets you Contact, success by 4+ or Critical Success gives you Identification. Subsequent successes as detection bonuses improve improve the "level of contact."

Contact = "You see a group of figures moving in the darkness."
Identification (with/without Comprehension roll) = "They're armed."/"They're Orc raiders!"
Detailed Identification (with successful Skill or Comprehension roll) = "They're a mix of ordinary Skullcrusher tribe orcs armed with spears or two-handed axes, and 4 well-armed & equipped elite warriors in plate armor with broadswords & shields."

This idea might have been dropped for GURPS 4E, but it's a useful house rule if you want to add a bit detail and uncertainty to Sense rolls.

Lighting Effects: A quick & dirty way to measure drop-off of lighting effects is to assume that each light source has a "Brightness Rating" (i.e., how many levels of Darkness Penalty it cancels) which drops by 1 per doubling of illumination range beyond the base range. E.g., A Torch with Brightness Rating 3 (reduces local Darkness penalty by -3) with 6 yard range would have Brightness Rating 2 (-2 DP) at 12 yards, 1 (-1 DP) at 24 yards, 0 at 48 yards.

Where multiple light sources overlap, use the highest Brightness Rating and possibly boost combined Brightness Ratings by 1 (i.e., reduces Darkness Penalties by an addition level).

To detect distant light sources, keep up with the reduction of Brightness Ratings over distance until -10 (for visual sighting), or greater than the Sensor Rating of whatever system is attempting to detect the light. On a dark night you can see a torch from miles away in the right conditions.

Bonuses to Visually Detect Groups: For a large group moving in roughly the same direction & speed, base Size on the narrowest dimension the group occupies +1. For example, 100 Size 0 soldiers moving in single file would effectively be Size +1. A group of soldiers moving in 10 ranks 10 abreast, spaced at 1 yard intervals, would have Size +5 (Size +4 for occupying 10 yards +1). A group of Size 0 creatures moving in loose order, at their own pace, with no particular formation, would be would +1.

Additional Sighting Bonuses: +1 or +2 if the target is backlit, "skylined" or otherwise stands out against their background; +1 to +4 if target is reflective or otherwise attracts visual attention. At night, bonuses for reflections, etc. shouldn't exceed +1. Most creatures are better at detecting moving targets (unless the thing they're trying to see is tiny or very fast), especially if they're traveling along a predictable path; perhaps +1 to +4.

Last edited by Pursuivant; 01-06-2023 at 02:47 PM.

 01-06-2023, 07:14 PM #9 Lancewholelot     Join Date: Aug 2004 Location: USA, Planet Earth, The Milky Way Galaxy Re: Distance for Hearing/Vision rolls? A group of 10 orcs moving at a run, presumably with arms and armor... Unless the caravan camp is making a lot of noise I'd judge the guard likely to hear them rushing toward him before he could see them on an overcast night. Still, even with a shout of alarm, the assault would likely be on him before help was roused.
01-06-2023, 09:51 PM   #10
thom

Join Date: Oct 2011
Re: Distance for Hearing/Vision rolls?

Quote:
 Originally Posted by Lancewholelot A group of 10 orcs moving at a run, presumably with arms and armor... Unless the caravan camp is making a lot of noise I'd judge the guard likely to hear them rushing toward him before he could see them on an overcast night.
Hmmm...I'm not so sure 'bout that. The orcs are moving at their normal speed, wearing leather armor, so that's not very loud. And I find the Hearing Range tables to be far less friendly for those who aren't exceptionally acute...

thom

 Tags hearing, vision

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