Thursday, February 9, 2012

A Symposium on Infravision

Let's talk about infravision.

I think I'll throw this one open. I'd like to know what you think. Andrej in my campaign, who is also James C., challenged the way I do things, and I am open to being challenged. Here's what James wrote:

"My feeling on infravision has long been that its application is arbitrarily limited somewhat by most DMs considering it thermal vision only, and further being limited to the extent of thermal imaging available with mind-20th century technology. There is more than just heat in the infrared range and all bodies (i.e. matter, objects) can both absorb, reflect and emanate infrared energy, which is simply a kind of light humans can't detect. Just as the human eye and brain can discern a multitude of colors (i.e. frequencies) and shadows (amount) of "visible" light... wouldn't one anticipate the same level of sophistication in the same organs that can "see" light beyond the normally visible spectrum?"

James makes good points, and it deserves discussion. Here are some relevant questions I'd like answered:

1) Is infravision definitively the detection of infrared light, or is it a differently originating ability that is merely similar to infrared light.

2) If it is the detection of infrared light, is it near-infrared, mid-infrared, or long-infrared? For definitions, and for general information, read the wikipedia entry. Is it thermal only, or can one detect dipole moments?

3) Should infrared be just as good as seeing in daylight? Should there be any restrictions to what can be 'seen'?

4) If (3) is taken for granted, should the 60 foot limit be thrown out? Is any range limit logical? And if there is one, does infravision end dead without any ambient radiation detected by the eye further out, as there must be with visible light?

5) Again, if (3) is taken for granted, what is the difference between infravision and ultravision?

6) Should it automatically be assumed that infravision-capable creatures are able to see perfectly out-of-doors, or should visible light spectrums be limited? What is the changeover time between infrared and visible light vision, if a user needs to switch from one to the other? Does visible light underground 'blind' infravision users longer than normal visible light users?
These don't represent all the possible questions, but they would seem to me the most pertinent for game purposes.

Please argue your pet position. Please restrain anecdotal references or personal experiences, and stick to arguing why one position is better for gameplay that another. Please consider the problem from a game perspective, rather than what "real" infrared vision would be like. The problem here is how to manage the game, not how to solve philosophical questions about scientific optics.

Go on. Take a shot.


Anonymous said...

You beat me to the punch. Regarding "switching it off" my pet position is that infrsvision is merely an expansion of a creature's visible light range. So, no switch on or off other than opening and closing your eyes.

JB said...

My thoughts are already permanently logged:

Perhaps not a logical argument, but fairly succinct.

Butch said...

I always played that infravision was simply the ability to see in the dark -- if no light sources were present. If you have a torch-bearing Human in the party, infravision doesn't work. Which usually made it useless unless you had a demi-human scout up ahead of the party.

I thought the point was to explain why orcs, goblins and trolls would sit around in dark dungeons waiting for adventurers to show up. Why didn't THEY need torches? Because they can see just fine in the dark! No wonder they get pissed when topsiders show up with their obnoxiously bright torches!

It wasn't until I started playing Shadowrun that I started treating infravision in the modern, seeing heat as color sense. That's because a) Shadowrun explained IR a lot better (and contrasted it with Low-Light Vision), and b) by then I had seen the movie Predator.

John Bell said...

I did some thinking about this a while back, and I decided that infravision in creatures like dwarves works like infrared sensing in snakes, rather than as true vision.


The reason is that sensing nearby heat sources in this way raises few questions and problems of adjudication than true vision does, while preserving the most useful elements of the sense (is there heat on the other side of this door; are there enemies nearby; can I attack in the dark without penalty?).

Wickedmurph said...

Hey Alexis,

Yeah, I'd still like to play. I'm on the road for work tonight (lovery Mississauga, Ontario!) but I'll put a character together and get him/her off to you tomorrow when I get back to my dice.

Alexis said...

Email me at and we'll sort it out.

Dave Cesarano said...

I think Butch's initial paragraph sums up the most simple, expedient way to apply infravision. You can see in the dark. All that stuff about heat or seeing like snakes, etc, that's simply flavor text, if you really think about it. In pure mechanical terms, the easiest way to utilize it is simply as a "see-in-the-dark" ability as long as there is no light source interfering. An individual DM's mileage may vary.

graham said...

1. Infravision is based on but not definitively the detection of infrared light because once you declare that it is, the need to adhere to realistic scientific limitations supercedes gameplay considerations.
This is unacceptable since there isn't actually any realistic basis for infravision. It only exists fantastically.

2. n/a

3. Infravision should not be "as good" as normal vision. There are things in the visible spectrum which are not in the infrared spectrum, just as vice versa. Reading depends on distinguishing tones and colors which can only be seen in the visible spectrum.

4. Any kind of range is arbitrary and should be chosen for gameplay reasons. The range of regular vision is determined by our ability to distinguish, not by the range of, light. So too the range of infravision. 60 feet is a good range because it is further than most light sources but not so far as to totally undo the dynamic of limited vision in the dark.

5. n/a

6. Infravision capable PCs should also be able to see the visible spectrum because total color and tone blindness is too extreme a penalty. Monsters can be limited.
If PCs can see both spectrums simultaneously the DM is responsible for including infravision details in what is described.
If PCs can switch between normal and infravision the impetus is on the player to ask for infravision information.
Infravision which only works in the dark is a less versatile ability, but easier to incorporate into the game. No need to worry about it most of the time, and when it is used it is mostly just used to compensate for the lack of normal vision.

One can use infravision to see temperature, normal vision to see color and tone, and both to see the shape and form of tactile objects.
Regular vision can see further but is limited by available light, and most portable light sources have a shorter range than infravision.
They are meaningfully distinct but both vald ways of collecting different information from the same environment.

3llense'g said...

My oppinion on my blog:

Scarbrow said...

I'll stick to the questions you presented:

1) Definitely yes. That way we can base edge cases on the "real world", taking it to the actual wavelength in case of doubt.

2) I'd say near-infrared by default, with certain qualities/races/powers/gadgets allowing for farther ranges. Reason? The closer to human, the easier to understand and the less unexpected complications (I can elaborate)

3) Yes. The limits are the physical ones, that is, you depend on what you could see for the given wavelength. You may need specific light sources to correctly "see" in some situations (that is, this would never be the same as "blind vision").

4) Completely thrown out, unless you consider an equivalent limit for usual sight

5) I recognized I'm not versed enough to be subtle, but the way I see it, ultravision is an extension of common sight through the high part of the electromagnetic spectrum, so it would work the same as infravision. Some beings could even have both, in different grades of intensity. You could even redefine normal sight as the lack of both.

6) I think the most flexible solution would allow for several (possibly overlapping) ranges of visions to be achievable through each kind of "eye". So no, having infravision/ultravision should not imply having "normal" vision too. You could perfectly be unable to perceive anything red and above (which wouldn't make you exactly blind). I could also elaborate further.

I cannot say more at the moment, will try to come later to participate more.

David said...

No suitable blog so a wall of text here.

The questions are great but I don’t see any reason to suppose that there is one position that is “better” for gameplay than another as long as the positions are consistent and the implications are given at least a modicum of thought when designing the world. I’ve gone for the semi scientific model.

Ultravision serves solely to add to the spectral range seen by a character. They see additional “colors” that others can not. In situations where there is ultraviolet light (for fantasy game purposes I treat this as outside for the most part although I often assume that magical light has a significant UV portion) someone with ultravision has bonuses to perform vision checks as they have more information coming in and thus are not as easily fooled by camouflage and the like. This partially negates low light or darkness penalties. Since ultravision depends on outside light sources it can not work in complete darkness. Ultravision thus operates mostly like improved normal vision.

Infravision is also an extension of the spectral range but it has some different implications. Similar to near IR photography it provides different info and can provide a form of night vision. As with ultravision, it’s not something that gets switched on and off. Users can just naturally see in different light. I have always assumed that warm blooded infravision users can see in the reflected light from their own body heat. Thus these creatures can see in complete normal darkness without penalty. The only limitation is that they can not sense fine details without normal light (combination of longer wavelength meaning less clear details and similar temperature of nearby regions on an object obscuring the details). Thus penalties to fine visual things if the character is depending on IR but no penalties on less fine visual checks (combat).

Any range limit on both visions should be similar to the range limit on a lantern or torch; a fading out not a sharp demarcation line. No difference in blinding although one could suppose a special UV (or less likely IR) light source that would only blind ultra or infra-vision users.
I’m with Graham, infravision capable PC’s should have normal vision also although at least some monsters might rely solely on infravision.

Anonymous said...

I considered a longer post on this on my own blog, explaining how I do it in my world, responding to each question in kind, but found that it got overly technical for a D&D blog, and once boiled down fit as a comment:

1) infra-vision effectively triples the range of "visible light" for the subject creature, to include all or most of the near IR spectrum (700 nm to 1400 nm... normal human visible light is about 390 nm to 750nm).

2)See # 1

3) If only infrared light is available, then I imagine it looks something like night vision goggles only with a red and not green palette. If normal light is available, the image is blended... these creatures always see the world through rose colored glasses. I chose red because Ir is closest to that on the scale and my players can more easily grasp that vs. "new colors"

4) Yes. Here's where I may fudge the science a bit everythign not at absolute zero (i.e. anything with moving molecules) emits near IR energy. Perhaps infinitesimally, but the sophisticated eyed of a creature able to see IR can take this and send it to the brain and get a red-washed image even in the absence of all light. Again, everything is an emitter for near IR. Unless the creature is in a void, they can see both reflected and emitted near-IR.

5) I discard ultravision... but simply extend the frequency range of visible light and there you go. Creatures able to see across all bands would need to have highly evolved brains. I'm thinking super-alines and Cthulhu here.

6) Case by case. Some subterranean creatures in my world see only near-IR, but that means they see fine everywhere but can't recognize colors or normally visible light. No blinding effect except where intensity is considered. (There's a lot more near -IR on the surface in daylight than in a cave.)

Butch said...

One more point. If infravision works in the modern, thermographic sense, doesn't it also (at least when dealing with warm-blooded creatures) act as a Detect Invisibility and Detect Life spell? Render a thief's ability to Hide in Shadows useless to demihuman eyes?

Can infravision be used to follow fresh footprints (they leave radiant heat behind)? See creatures behind curtains or even behind thin walls?

Just how powerful do you want this ability to be?

Anonymous said...

If you keep infravision to the near IR range, there is no thermal effect... heat has much larger wavelength and would remain invisible except for very hot things.

Scarbrow said...

I like Butch's suggestion

Personally, I like powers to be customizable, and how powerful the IR sense should be (or in physical terms, as Andrej very well says, how far into the longer wavelengths legion will it reach) depends fully on what the DM wants to rule. So, DMs should be aware than allowing more "powerful" infravision can quickly become a game-breaker.

About blinding, I just came to realize that a torch (and almost all non-magical light sources) are powerful heat emitters, so they would surely blind (or at least cause some discomfort) to creatures that can "see" the appropriate frequencies. The fact is, almost any system (and certainly all for middle-ages tech level) relies on fire/heating an object until it emits wavelengths of the appropriate frequency (visible light). And as a rule, to emit visible light you must emit a lot of "lower" wavelengths (infrared), so any mildly-bright visible light would be a very powerful IR light source. Even more so for UV light - an object would need to be even hotter, and thus, a mild UV light would be a brilliant "visible" light source, and thus an unbearably bright IR light source.

Which brings again the option to "shut off" the IR sense. It seems that, in light of this discussion, being able to shut off that sense , "close the IR eye", would be a definite evolutionary advantage for races having that ability. Allowing it or not, and thus developing the blinding rules, would need to go hand-in-hand. Even if the same physical organ (eye) is used for all the light, you could have another separate eyelid, or an equivalent to the pupil. But I would probably bet for an entirely different IR-receiving organ.

I think that "lighting" by using own's body heat is a bit far-reaching. As a maximum, that could be used as a way to spatial navigation, like electric eel's. It would probably extend your "touch" sense rather than your "vision" sense. And also, if you were to be so sensitive, to the point of needing so little "lighting", you would leave yourself very vulnerable to blinding from something as hot as a torch.

Anonymous said...

I love the idea of dwarves, orcs, goblins etc. with furry "heat pits" at their temples. Or cheekbones. Maybe that's why female dwarves have beards?

Tom said...

Just a quick comment-on-a-comment. Blinding Ultra-Violet vision is harder than you might think in the Natural world. Electro-magnetic energy is emitted when electrons are excited around a nucleus, the more excited they are, the more energetic the light they emit. The problem is that Ultra-Violet light can only be emitted from electrons that achieve 'escape velocity' from the nucleus. Since they aren't part of the atom anymore, they don't cause it to do anything.

This was first noticed with metal. You heat it, it gets hot, then red-hot, then white hot. But it never gets 'ultra-violet' hot. Scientists called this the 'Ultraviolet Catastrophe' and it's one of the things that led to Quantum Physics.

So no Ultra-vision Blinding lights, at least without magic/alchemy.