Monday, March 25, 2019

Infravision Instances

I've spent a silly amount of time recently thinking about infravision. In particular: Should it be nullified when nearby to a torch or lantern? And what is the point of that rule in the first place?

See, in OD&D by the book there is no such rule for infravision being spoiled near artificial light. It seems like a rule that Gygax came to between the OD&D and AD&D publications. It is on AD&D DMG p. 59. It was missing from the Holmes Basic draft manuscript, but was added for publication, presumably by Gygax (p. 10; see Zenopus Archives). We're told by Ernie Gygax that what Gary had in mind was specifically this scene from the original Westworld (1973).

But it makes so little difference in-game that I've been ignoring that rule for a long time now. The DMG says, "It requires not less than two segments to accustom the eyes to infravision after use of normal vision" -- two segments being a small fraction of a round, so I'm not sure how that would ever make a difference in play. I suppose there's the range issue: infravision is 60', and torches as of AD&D light a 30' radius, so I suppose that cuts down the distance. But on the other hand, OD&D says that monsters are seen at 20-80' (Vol-3, p. 9), and AD&D likewise says "A light source limits the encounter distance to twice the normal vision radius of the source" (DMG, p. 62) (as well as real-life experiments supporting the same thing, here; login required) -- so it seems like effective visibility is back to at least 60', equal to PC infravision. Moreover: I'm pretty sure none of us play like the monsters are blinded by PCs with a torch as in that Westworld clip, right?

So in these cases my approach is usually to research what would happen in real life as always the most solid, stable, and consistent way to play it. Previously I've used thermal-vision goggles as a serviceable model. Looking for real-world biological organisms with infravision is somewhat more elusive. Interestingly, there seems to be a lot of active progress in this area in recent years among biology researchers:
  • Snakes have specialized heat-sensing pits on their heads (2010).
  • Mantis shrimp can see deep into ultraviolet and deep red wavelengths (2014).
  • Zebrafish and bullfrogs produce special chemicals that can situationally shift their vision to near-infrared (2015).
Then, most incredibly on the day that I wrote this post, a new piece of research broke: Researchers in China and at U. Mass injected nanoparticles into the eyes of mice, altering them to perceive near-infrared light -- and this might soon work for humans. Pretty amazing! The claim also is that this treatment leaves the standard visible-light perception unchanged.

For all this, the burning question remains; if an infrared-sensitive creature stands near a hot torch or lantern, is its infrared visual capacity ruined? This does not seem to be a thing that anyone has tested to date. In fact, a few weeks ago I emailed one of the leading researchers in this area and asked, "If there is prey nearby and another very hot artificial source (say, fire), does the animal fail to detect the prey?". He kindly took the time to reply with: "Daniel, I don't know the answer to your question" (and also sent the inquiry to a second researcher). So: Still unknown as far as we can tell from current state-of-the-art science.

But I still can't quite see what the point of that rule was in the first place, actually. Perhaps it's just a totally academic issue.


17 comments:

  1. This is really interesting. Do you use infravision much in your games? How do you treat light sources in general? I find that I tend to forget completely about it.

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    1. Occasionally I forget, but my intent is definitely to verify who's carrying light where in the party, and be ready to penalize them it gets blow out or lost. I've definitely waved the switch to infravision for some time now.

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  2. Some time ago, maybe even before 3rd edition gave us "low light vision", I had decided that Infravision was more like night vision goggle and less like "Predator", partially to sidestep a lot of this. (All respect to Westworld and Ernie) Sure we lose some of the cool imagery from D&D fiction.

    Does 0D&D or AD&D have rules for regular human night vision being spoiled by a sudden bright light? If we dont want to simulate that level of complexity for normal, vision, its probably best leave this in the land of Ad-Hoc ruling for clever players.

    Plus, how does Hide in Shadows work in a world of Infravision? can you Hide in Thermals?

    Same as Enzo, i just tend to forget about lighting and vision until it comes up. Generally you can see, can't see, and will deal with in-between/corner cases when they become relevant.

    Not really an answer, just more questions.

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    1. I think I agree with you on those observations, esp.: not simulating a switch in human night vision. I do like my PCs to feel a bit constrained with light and who needs an extra hand to carry out. Also I'm prone to hit them with effects or spells that turn off the lights.

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    2. Thinking on it more, I wonder if a general rule would suffice.
      Sudden changes in visual conditions = Save vs Spell or "dazzled" (or blinded?) for 1 rd

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  3. I find this idea is more usable as a game balance issue than anything else. By requiring the dwarves et al to consider this limitation when making use of this game-changing trait, they have to put themselves at risk by venturing forward alone. Until they do that, the terrifyingly oppressive darkness of the dungeon affects them as it does others.

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    1. Well, let me ask: What advantage are you thinking of over just using the party lght in the first place?

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  5. I actually ignore this and play by the "magical underground" rule that monsters see in the dark. Characters do not. If the party charms a monster and it joins the adventurers it magically is unable to see in the dark. The necessity for a light source and the fear of total darkness is a big part of "dungeon horror",at least as I see it.

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    1. Yeah, I don't play that way, but I'm quite sympathetic to the motivation.

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  6. Thanks for sharing this! It is very interesting and extremely inspiring.

    Although I don't usually care about the details of infravision (as opposed to darkvision), this post has inspired me to consider the effects of darkvision in encounter distance, something I had previously ignored and seems to have many interesting implications - like seeing eyes and silhouettes in the darkness, for example.


    I hope you don't mind me linking it:

    http://methodsetmadness.blogspot.com/2019/03/encounter-distance-light-vision-etc.html

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    1. Excellent thoughts. Thank you for sharing!

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  7. In my houserules I have infravision and night vision. Night vision is like cats and other animals. Infravision is just like normal vision but with a 4th primary color being in the infrared spectrum. Creatures with infravision always see in 4 colors, they can't turn it on or off, only time they would only see infrared is when it is pitch dark and there is a heat source that doesn't emit light in the standard visible spectrum. So having bright lights or a fire wouldn't interfere with their vision any more than normal.

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  8. Does this also mean that most undead are "invisible" to those using heat-based vision?

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    1. Well, that's an interesting question and the last time it came up I might have wavered on that a bit. Looking at the AD&D DMG, I would tend to say "visible" for at least two reasons (p. 59):

      (a) "if you are generous, you can allow different substances to radiate differently even if at the same temperature... Note that air currents might show as cold or warm layers."

      (b) "Creatures with infravisual capability of unusual nature, such as those which see infrovisually to 90', are actually emitting infrared radiation from their eyes... The eyes of all such creatures will appear as very brightly glowing red when observed by any other creature with standard infravision."

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    2. I think I remember that passage. But I guess I'd still want to assign a negative to-hit mod as if partial cover. Swinging at two-points of red light seems harder than seeing a full target.

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    3. That's perfectly respectful. On the other hand, one might argue if that "emission" lights up everything well enough for the monster, then so too for any PCs with infravision in the area. Just a thought (not that I specifically apply the "emission" rule myself).

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