I am often asked what the point is of introducing scientific data, reasoning, or logic into a fantasy game world. Considering the PHB even suggests this may be unwise, I'm not surprised many people wonder about my predilection for doing it. But I have my reasons.
Even though we are dealing with fantasy and games, things SHOULD make sense on some logical level. Several ways can be found to do this, but the scientific method is a good one since it readily lends itself to believability, logic, and the natural conclusions we can already draw from the real world while using it. Unless one doesn't mind - or actually enjoys - having things make absolutely no sense in their games - most probably because they have no desire or ability or inclination to figure things out for themselves - then some measure of consistency should be introduced. Only with this level of detail can our characters ever hope to realistically use clues to figure out puzzles and complete their quests. If things don't have to make any sense, what's the point of intelligent and/or wise playing?
Is this harder to do than ignoring such things? You bet it is; no question, just as it is harder to write good fiction than to write crap. But by paying attention to detail, your game may reap the benefits of the reward, most notably the freedom from the tired old phrase, "It doesn't have to make sense; it's just a game."
Besides, should one 'accidentally' learn something about the real world while playing, where's the harm in that?
Yet, this does not mean everything must be explained in excruciating detail, nor do you have to be an expert in science to do this, or particularly skilled in the scientific method to at least use the more scientific guidelines once they are suggested or given.
And let's not lose sight of the fact that some things simply aren't real, so they have no natural counterpart in our real world. Yet many things may. And when we introduce some explanation or justification for a rule or an ability, we can do more with it. We just have many more options to play with. It's like increasing your toys for no extra money. More can be ascertained using it, thinking about it, and cleverly devising new methods of use. It makes the game that much richer in detail and believability when we do this. So though not everything will be, or even should be explained with scientific clarity, a lot more of it can be than most people might initially think.
In particular, I wish in this article to delve into the matters of infravision, ultravision, dark vision, and normal color vision. I will mostly deal with 2nd edition AD&D, but also touch on 3rd edition D&D at the end.
Despite what you may have heard or have inferred from many children's pictures, the sun is not yellow. It is a white star, radiating light from the ultraviolet, the visible, and finally the infrared spectra. The visible spectrum covers the range of white light - the presence of all visible colors. It is visible to us since our eyes evolved under this sun and some of this radiation (information) at those frequencies (colors) proved useful in survival - at least surviving long enough to propagate by having children - who not coincidentally inherited our eyes. The statement, 'Oh, you have your father's (or mother's) eyes' is no joke.
In fact, since snow (frozen water) scatters virtually all colors across the visible spectrum equally well, you can tell what color a planet's sun is pretty much by what color the planet's pure snow is. In Earth's case, it is white. But I digress.
White light can pass through a prism and bend. Each frequency (color) bends more or less than the others, so the light is separated into the color spectrum. Roy G. Biv is a name you should learn. It is easy to recall and highly instructive as a mnemonic device or memory aid. It simply helps us recall the natural order in which the colors in the rainbow appear. (Rainbows use water raindrops as natural prisms). Roy G. Biv, thus =
For the most part, in simplest terms, when light hits an object it tends to absorb most of the radiation - probably heating up. White objects reflect nearly all light, so they do not heat up much in comparison to dark or black objects that absorb nearly all light and can become quite hot. But usually a few particular frequencies don't absorb well and those are partially bounced off and reradiate back. The particular frequencies that are most strongly reflected are what we see, and this is taken as the color of the object.
For example, an apple is hit by white light and absorbs most frequencies, though much is redirected or bounced off. But the red frequencies are absorbed least, most strongly reflecting those outward in all directions - like a stone hitting the pond, sending out circular, ring-like waves, or in three dimensions, concentric, sphere-like waves. Those who have color vision in the red range can see this as a red apple. If illuminated with some different colored light - other than white light, or white light that is missing its red component - you will see strange results. This is why colors look so strange under black lights, for example.
The sky appears blue since nitrogen molecules scatter some of the blue components well and in all directions, thus making our sky appear blue. Most of the rest of the visible spectrum simply passes though the air. Thankfully the majority of the ultraviolet components does not pass through and bounces off, never reaching us. What does come through can still cause sunburns, however. These ultraviolet components are also part of the basis for ultravision.
The sun often is taken as yellow, or when particularly low in the horizon, perhaps even taken as orange or red. This is because by the time all that light goes through the entire atmosphere - more of it to go through when at lower angles - certain colors are scattered out less than the others are. We see the ones that remain, and this is the apparent color of the sun. The higher the sun is in the sky, the harder it is to even look at - even causing pain and blindness if one isn't careful. But if you look, it is whiter while closer to noon. The lower the sun on the horizon, the easier and safer it is to look at, with more air, more dust, and more pollution, etc., to filter out some of the harsher elements. It is then that you may notice various other colors being scattered out. This is also when most people do look at the sun - at least for longer periods - and this is perhaps why they think the sun is yellow more often than not since the only time they tend to look at it, it does seem yellow. Similarly, the moon may have some unusual colors to it while lower in the horizon. Also, while the sun is low on the horizon and scattering so many colors, this is the reason sunsets and sunrises are so beautiful. Sunsets are supposed to be more so only because the day's activities have kicked up more dust, scattering more colors and painting a richer scene - so they say. But I digress. I digress a lot, apparently.
WARNING. Do NOT look directly into the sun for any extended period of time no matter how comfortable if may be. It is dangerous.
Out in the empty reaches of space where there is no air to interfere with our sight, Sol is simply a white star - more or less by definition. But this is not an astronomy lesson.
Some materials are opaque to certain frequencies (colors). This means light of that color (frequency) will not pass through. Other materials are translucent or transparent to a particular color. This means light of that frequency will pass right though it. Most glass, for example, is transparent to the visible spectrum, but opaque to some infrared radiation. This is why a green house lets light in but doesn't let heat out. This is also why the 'green house effect' is a problem since carbon dioxide and some other gases are transparent to light but opaque to heat - infrared - thus letting sunlight in, but not as easily letting the radiated heat out, hence warming the Earth.
Our eyes have two types of light sensitive receptors, and by the time our brain gets done playing with the information these nerve endings send to it, we interpret this as color and brightness. Cones and Rods at the back of the eye do this for us. The Cones register color and the Rods register brightness. (Cones and Rods are so named as the nerve endings have these characteristic shapes).
For the most part, there are three kinds of cone receptors, for blue light, for green light, and for red light - the primary colors. If there were more, we would have more than three primary colors.
When your cones are working properly, you have 'normal' color vision - normal for humans, anyway. However, in some people and in some animals, these cones are weaker or fewer than they could be, or perhaps even nonexistent. If they do not exist, then that animal cannot see that color. Similarly, some say their color vision is a bit better than normal, as their cones are slightly more sensitive.
Many animals do not have any cones and are therefore colorblind. Some do have these cones, however. Primates - humans, monkeys, apes, etc. - birds, some fish, and some insects are the most notable of these and thus they have superior color vision compared to most other animals.
Cats do not have some cones while they do have others, and though they can see different shades of blue and greenish yellow, cats cannot see orange and red; these colors probably appear white to the cat - only their rods detect them. NOTE: how a cat's brain interprets this data is questionable, so if it 'sees' what we see, we cannot say, but it can detect differences in these colors (frequencies).
No humans have cones that detect in the infrared or ultraviolet ranges, so no humans can see infrared or ultraviolet radiation.
Some humans have weak, fewer, or defective red, green, or blue cone receptors. For myself, I have what is called a red/green deficiency, meaning my red and green cone receptors, though they are there, are weak or fewer - I'm not sure which - and work very badly. My blue sensitive cones are fine. If something is pure green, I can see this as green. If something is pure red, I can see this as red. True, they are not as vivid to me as people with normal color vision will see them, but I know what color they are. So red to me is a rather dark color, but it looks bright to normal vision.
However, many things are not purely comprised of only one primary color. Take new grass, for example. White light hits it and it absorbs most of this, but radiates back strongly at the green and orange frequencies - chlorophyll is green and carotene is orange, like carrots. The orange light so overpowers my weak green receptors that this green is totally washed out. I see only orange grass. An evergreen tree, on the other hand, looks green to me since it has no orange carotene - only green chlorophyll.
Oddly enough, such color 'challenged' people were sought out as bombardiers in world war II - or so I'm told - as poorly made 'green' camouflage often stood out against the orange grass. Bombs away!
Similarly, purples - red and blue mixed together - simply look blue to me. Other mixed colors can give me problems too, and other cones may be weak or fewer in other people or other creatures, giving them different kinds of color vision problems than I have. And color challenged individuals have even greater problems discerning colors in low light than normal people may have. Poor illumination often yields poor results.
The point is, however, to get you thinking about what may happen when some receptors are weak, deficient, fewer in number, or just missing. And what's more, to get you to think what it might be like if someone else had extra kinds of receptors in the infrared or ultraviolet range. To their minds, so-called normal vision types would be the ones who were colorblind. In fact, they would probably have many different names for various shades of color than you can possibly imagine. Just look at all those crayons in that giant box, and those are made only using three color receptors for (RED, GREEN, and BLUE). Add one or two more kinds of primary colors and the possibilities are staggering. But unlike the crayons, most things don't have their color's name printed on them :-(
By the way, perhaps you may have missed this, but the spell Cure Blindness, or now, Remove Blindness, is supposed to be able to restore 20/20 vision as well as fix colorblindness. Wow ;-) Of course, a tough DM may make you cast it twice if you need it to do both.
Infrared radiation is normally invisible to humans, lying just below the color red on the electromagnetic spectrum. But like normal visible colors, this area can be subdivided into several regions - colors or shades. Near, Middle, and Far - or Deep - infrared, in particular, are often described. In a way, the near and middle infrared spectra can really be thought of as one or two new primary colors that most people simply cannot see - though some animals can see part of this, such as bees, for example, where they see the color of flowers differently than we do, particularly in the ultraviolet range.
But for game purposes, we usually have to delve into the far infrared. This is where low temperatures - another kind of color - can actually be seen. I mean low enough so normal body heat would register. You have to get this low or deep into the infrared to actually see radiated body heat.
The hotter the object, the stronger the heat signal it gives off, the brighter it appears in this spectrum. If it gets hot enough, it will begin to glow red and finally white hot in the visible spectrum as well, but such temperatures are much higher than the insignificant temperatures at which our bodies operate.
Be advised. A creature with infravision NEED NOT have near, middle, AND far infrared receptors. Unless you wish to play with hundreds of new shades of color, it may even be wise to assume such creatures do not have near and middle infrared vision, but only have far infrared that developed and evolved independently for other survival reasons - like finding food, or avoiding becoming food. Continuous spectrum vision - from visible all the way into deep infrared - is not required and I recommend against it - for player characters, anyway.
But unless we insist on color vision while using infravision - and we don't, usually - and we limit ourselves to black and white and shades of gray only, the infrared receptors may be more like rods than cones, or they may have a third shape for all we care. (Disks or spheres?) Such receptors would absorb infrared light and send that information to the brain and let it interpret it.
One of the problems of infravision is likening its sensitivity to that of modern night vision equipment, thus being able to discern temperature differences of only a few degrees. If one could do that, they could follow footprints by their heat before they cooled down, see tiny animals with surprising detail - even hundreds of yards away and while they were hiding under dense foliage - and do other things the game probably never intended. AD&D infravision was never meant to be THAT good.
But if not, why not? Assuming one can see into the far infrared at all, why can't they see this stuff like our modern night vision equipment can?
One problem is lens size. Eyes would need to be about 5 to 10 times larger than they are to gather so many weakly energetic photons. True, whereas Sailor Moon and many other anime characters have the eyes for it - the kind of eyes some people would kill for - most humans do not have eyes that big.
But a bigger problem is such equipment must be cool in comparison to what it is looking at. Otherwise it is like looking at a match in front of the sun or a firefly resting on a light bulb. And unless creatures with infravision are deathly cold to the touch, their own body-heat greatly limits what they can see.
Science demands we keep track of where energy comes from and goes to. It cannot simply be created out of nothing nor destroyed and vanish into nothing. But there is an answer for that on such high fantasy worlds. For a real world comment of thermodynamics, and the mistakes some people might make about them, check this aside:
A Brief Aside On ThermoDynamics (Two Common Erroneous Misapplications Of These Laws In Regards To Evolution)
Certain worlds are located in certain areas of the galaxy where the fabric of space is weaker and bridging the gap between the prime material plane and other planes of existence is easier to do. This is more fully explained if you follow the link immediately below.
The Magical Evolution Of Worlds (Why Some Worlds Are Magical And Others Are Not)
In fact, it is so relatively easy that this becomes an evolutionary force or trick, and evolving creatures may stumble upon such things through mutation and use this as they evolve.
One of the nicest things about magic - interplanar - more than one plane - manipulation of energy as opposed to intraplanar - only one plane - manipulation of energy - is that energy may be brought in or taken out through magical means; it is not created or destroyed, but obtained from or sent to elsewhere. You can really see this at work with spells like Continual Light, Continual Darkness or other long duration spells, or understand better what the Permanency spell may be doing.
When this happens, certain cellular functions may capitalize on the fact that they can be hotter or colder than one may normally otherwise expect them to be. Lots of magical creatures are magical simply because they have stumbled upon such a thing though mutation, it had survival characteristics, and their offspring inherited them.
Be warned, however, that ancillary functions along these lines are nice and sometimes advantageous, but primary ones can be just as lethal. For example, if one intersected with a Dispel Magic Field or Anti Magic Shell, such magical functions would temporarily be cut off. If your infravision quits working for a time, this ancillary function is no great loss. If a creature's primary function is interrupted - like a massive heart stops pumping since it was partially run with magic in some way to operate a heart so large - it will die. As there are numerous natural and artificial ways to temporarily interrupt the flow of magical energies - we just don't notice them all that often since we aren't magical - primary biological functions often become a lethal trait rather than a survival trait. This is why most such functions are not lethal should they temporarily fail. (Such mutations died off and didn't reproduce, leaving only more ancillary type functions, like infravision or ultravision).
Nevertheless, since some areas have a tendency to be less stable in regards to magic, highly magical creatures may simply avoid living in such a niche. Other areas may be incredibly stable, however, so even some primary biological function may become enough of a survival trait to pass on to their offspring, provided the creatures tend to stay close to such stable areas of high magic. In fact, sometimes this is the hidden reason why creatures live in and defend, or avoid certain areas, even though no other 'apparent' reason can be 'seen' by conventional means.
NOTE: Mages and Clerics often like to find such areas of stable high magic to build their keeps or temples, while warriors sometimes like to find such areas of unstable or low magic for their keeps and castles since they are not as vulnerable to magical attack.
Also note, certain magical functions may simply stop working while on other planes of existence, as they never evolved on those planes. Creatures native to such planes do not have this problem, so this consideration is mostly for those who travel between planes using artificial means - like the Plane Shift spell. Your local DM will have or make these details. But I - yes, I know - digress.
The point is, that with extraplanar energy heat sinks and sources, it is possible to suggest that SOME infravision may be partially magical, and that such eyes - the extra sets of infrared cones or rods or whatever - bleed off thermal energy to elsewhere, making the eyes slightly cooler than the rest of the body, and enabling them to see with some distinction into the far infrared range without their own body heat spoiling their infravision. This is why infravision is soooo cool ;-) Of course, such things may also have to have special tissues that thermally insulate well.
Naturally, there are other ways to do it. Eye stalks, like a crab or a beholder are far enough away from the warmer, main body and may be sufficiently air cooled, or cold-blooded creatures may not require any magic to make this work.
However it is done, this still shouldn't be sensitive enough to discern heat differences of a mere few degrees - unless we are actually cooling down the body or the eyes to a more icy temperature, or at least a lot colder than most warm blooded types. So one cannot normally see footprints, normal colors, or even more than vague outlines at a distance. The closer, the larger, or the hotter the object, the better your chances at discerning what it is.
In addition, we adopt another point of view by looking at our friend the cat, thus finding another factor in our analysis.
Cat's eyes open wider than human eyes, thus allowing not so much an amplification of existing light, but a utilization of more of the available light. (Nothing is being amplified since 'amplification' implies more energy is being added, and in quite clever ways too, so we avoid this notion). Remember, even a cat cannot see in total darkness - thank god for whiskers. Furthermore, the back of a cat's eyes reflect back some of this light upon the light sensitive receptors, thus letting it see more. A cat sees about 6 times better than a human at night. Not six times further, really, but as if it were 6 times brighter, which may translate to some greater distance, but how much is questionable.
NOTE: I am not suggesting cats have infravision. They do not. Well, normal cats, anyway.
Thus, the better a creature's infrared range, the greater control they may have on their pupils, and/or the larger their eyes, and/or the cooler they are in relation to the heat source, and/or the more reflective capability they may have - like a cat. Some may even have eyes that glow in the dark like a cat - reflected light.
The idea a creature's eye generate beams of infrared light gets to be too problematic to stomach. Greater ranges of infravision will not be handled in that fashion. See 'Active Infravision' below.
Your DM may rule certain creatures with exceptional infravision - 90 or 120 feet - may have eyes that reflect in the dark like a cat's - they may even make your character's eyes do this if they think it's neat. But this is not because such creatures are emitting heat beams from their eyes. Get real. It is only because their eyes are WIDE open and they may have this reflective, mirror-like property just as a cat does, so if the light hits it just right, they may shine back at you. The mirror like ability may reflect both visible light and infrared, or only infrared. If only infrared light is reflected, then only creatures with infravision would see this reflected light, and even then only if it is within one half the range of their own infravision. See 'Mirrors And Infravision' below.
Putting limits on how far certain illuminations carry is sort of silly. 'This far but no further' just doesn't wash. As long as one has a clear line of sight with no intermediate opaque barriers in the way, you should be able to see something.
However, the total heat energy remains the same. Like an expanding sphere with an expanding surface area, the brightness - heat level - drops drastically as the surface area increases. This follows what is known as an inverse square law. The further away it is, the cooler it will look, until eventually it is too cool to see with infravision.
The surface area of a sphere increases as the square of the distance from the light source. S=4(Pi)R2. Thus, if you double the distance - R=2 - the illumination drops by a factor of four - 22=4. The same energy is now spread out over an area four times larger than before - R=1. If you quadruple the distance - R=4 - the illumination drops by a factor of 16 - 42=16 - the same energy now being spread out over an area 16 times as large as before, etc. Eventually, the illumination just gets too low to be useful at discerning detail, or too low to even register with such poor receptors, so your character might not be able to tell the difference between a bat 30 feet away or a red dragon 300 feet away. But like a campfire in the night, something might be seen - absent other light or heat sources. You just have no idea what or even necessarily how far away since it could be cool and close just as easily as it could be hot and far away.
How low is too low? It perhaps depends on how cool your eyes are, or how well you gather infrared radiation, and other similar factors. Once the heat gets much less than the temperature of your eyes, it is unlikely you can discern such objects anymore. If our standard becomes the heat a typical man gives off at 60 feet, we can guess where things should fall when they are hotter or colder, closer or further away. But there is no magical barrier at 60 feet, for example. That measurement only suggests where a man might fade from infrared view - probably since the heat from a man at that distance is comparable to the heat of your own eyes. A hotter but further object, for example, could still be seen past 60 feet, so these limits are not meant to be absolutes - like some magical barrier. Other factors are also involved, so there is room to play and make adjustments.
If we accept 3" - 30 feet - as a minimum range on infravision, then since under an inverse square law, the different ranges on infravision - 30, 60, 90, 120 feet - are not 1, 2, 3, and 4 times as sensitive as 3", but 1, 4, 9, and 16 times as sensitive as 3" infravision. That is, 12" infravision is 16 times more sensitive than 3", 9" is 9 times more sensitive than 3", 6" is 4 times more sensitive than 3".
Greater range sensitivity may simply translate to how far they can see the same heat, and NOT how much better they may differentiate between a few degrees. Thus, 12" infravision can't tell what something is any better than 3" infravision, but they can see it from a greater distance, whatever it may be.
However, the DM may allow those with 90 or 120-foot range infravision - greater sensitivity - to differentiate with greater clarity - see more shades of gray - and tell more - perhaps even follow hot footprints - but ONLY when at distances closer than 10 to 30 feet. This would be similar to letting 30 or 60-foot infravision capable people still see hot things when within 10 feet even if normal infravision may not be working - like elves may better discern secret doors even in the light, for example, due to slight temperature differences, but only if they are within 10 feet of the secret door. Of course, an elven mother wouldn't have to kiss her child's forehead to see if they were running a temperature then. She could tell if they were by looking at them, assuming she was within a 10 feet of her child in the dark, or a few feet in the light. That's sort of interesting, don't you think?
I suppose one could work out exact numbers and a formula, first using - Temperature x Profile Surface Area - and then taking into account certain ratios: E(1)/E(2) = [R(2)/R(1)]2, but we have no hard numbers on exactly how hot most fantasy creatures are anyway, or what profile they are presenting - which may change even by simply turning sideways. The matter is further complicated by the fact we must deal with multiple sensitivities (ranges) of infravision, knowing that certain clothing or coverings may more effectively hide this heat, often depending on how long they have been worn, and finally, different air temperatures or other medium - like fog - may deaden the incoming thermal energy. Once we go this far, we are not playing a simple game but are actually doing science. (Well, sort of. Scientists often don't calculate such things so much as they simply measure them with instruments). You can make all sorts of calculations and build various tables for each sensitivity, various ranges, and different heat levels if you enjoy tedious calculation of that nature, but most of us don't.
At best, we wish to know in general HOW it works so we may adjudicate a fair, but rough guess, and take into account when, where, and why other factors come into play - like when that thief is hiding in front of that hot wall of bricks.
All of this can be simplified by just using ranges, but it would be a mistake to think a 60-foot range means one can see ALL the heat sources within 60 feet, no matter how small, and NONE of the heat sources further away than 60 feet, no matter how hot. There is nothing magical about the distance of 60 feet. Similarly most light spells may have 'useful' radii of effect, but those outside that radius can see such things, even if they are too far away to 'read' by that illumination. The DM just has to consider these things carefully and decide what is reasonable and fair when determining what can and cannot be seen.
Unfortunately, more often than not, life is too prolific and abundant and at varying degrees of distance to think too much about every vague blip on one's heat radar, and such information is often ignored, unless one wishes to spend the majority of their lives tracking down every little creature that crawls in the bush or flies in the sky.
We may simply say that in certain ranges "useful" information may be gleaned - as given for various creatures with infravision, like 30, 60, 90, or 120 feet - and beyond certain ranges, normal heat vision will not register. If we do this, that does not mean all infravision stops at 60 feet - or whatever. We assume a medium object with medium heat - like a man - will no longer register past 60 feet, but a red dragon at 80 feet sure as heck still will, for example. A tiny bat - with heat less than a man - will become invisible to infravision at a range even closer than 60 feet. Exact calculations are left to the interested parties, but roughly guessing is a good alternative - or eyeballing it, you might say.
It probably should take at least a round for eyes to adjust from normal light to infravision or vice versa, but it may take longer. If a particular creature's infravision is more dependent on the opening of the pupils rather than the other factors, then for that creature it may take longer and have greater adverse effects from sudden changes in levels of illumination - such as temporary blindness.
NOTE: Even normal vision has difficulty adjusting to rapidly changing levels of illumination. Pirates, for example, often wore eye patches over one good eye - not because they were blind in that one eye, but because they often had to quickly go below decks into the dark. Changing the patch from one eye to the other allowed them to function without pause, but if one had to wait for their eyes to adjust to the darkness, that could take several minutes, which they could hardly afford during a pitch battle. Arrghhh, Jimboy, where's the powder me lad?
Again, infravision is not something a character turns on and off at will. It just happens. Furthermore, though there is something to be said for sudden changes, I doubt one would be totally blinded if they suddenly looked at a new, unexpected heat source - like a Burning Hands spell. Rather, the infrared receptors would simply be overloaded for a time and they would become infrared blind, but their normal vision would be unaffected, or at least no more affected than expected for one who has normal vision going from darkness to torch light. So if a torch appeared from around a corner, one might be blinded in the infrared range, but normal vision will kick right in with no adverse effects. Normal vision always supersedes infravision. You could be temporarily blinded on both fronts, however. A Fireball FLASH!, if it would blind a normal vision person, would blind an infravision capable person on both fronts. (Recall infravision is not continuous spectrum vision from visible to deep infrared, but discontinuous vision including both visible and deep infrared, but not near or middle infrared).
Similarly, any light source - like a torch, lamp, or even a candle, if it was close enough to provide 'useful' illumination - was in their infravision 'range,' then their infrared receptors would simply be washed out - like my red or green receptors are when other more prominently perceived colors come into play - and superseded with normal vision. Thus, normal daylight - before sunset - torches, campfires, Continual Light Rocks, etc. would simply, though temporarily shut off infravision. It may still take one or more rounds to readjust to the new, lower illumination conditions after such sources are removed or blocked off.
If the DM plays with these rules, they should develop an appreciation for what the world may look like through infravision. Here are some tips:
Though you may think steel or that toilet seat is colder than the surrounding air on some frosty morning - since it feels colder when you touch it - it really isn't colder - usually. It is the same temperature as the rest of the room. The only reason it feels colder is because it is an excellent conductor of heat, thus drawing off your body's heat very rapidly - much faster than the air - therefore feeling colder when you touch it. But most things soon reach ambient temperature. Therefore, the vast majority of objects all look kind of gray and you really can't tell anything apart after a time. Unless it is actually generating heat of its own accord, or something is drawing off its heat faster than normal, it typically will not stand out. Cold water pipes may make a toilet reserve tank look colder if it were recently used, but usually hot water pipes are used to prevent excessive condensation. Not that the water is hot, really, as it has been sitting in the pipes for a time - out of the water heater - since the last flush, but it sure isn't cold either. But I digress.
However, moving air and water often help adjust temperatures quicker and such things may stand out, particularly if recently used. A hot water pipe may normally look gray since the water inside it is no longer in the water heater and has had time to cool down, but if someone in the house was just using hot water, it will look brighter. Of course, such pipes are often well insulated too, so you may not see them after all.
Rocks and water, bricks and tar, plants and air absorb heat during the day while the sun shines on them. At night they give up this heat, but this takes time and they each do it at different rates. During the early evening hours one can see these changes and differences. Land heats up quicker than water, but then so too does water retain this heat longer than land. If you can just guess what its temperature would be, this will give you a good idea of what it may look like.
NOTE: Infravision capable people probably enjoy watching the scenery at sunset and into the night for a time more than humans since they can see the heat slowly fade and have many more interesting things to look at and think about while relaxing and having a brew after a hard day's work - I assume. Unfortunately, a good pipe, cigar, or cigarette is not an option if you wish to enjoy this thermal decline. It would probably spoil the view.
Ambient temperatures look gray. Colder temperatures look black or darker. Hotter things look whiter or brighter. Many temperatures are possible; so many shades of gray can be used. The more sensitive infravision is, the more shades of gray may be seen.
Anything giving off too much heat or light will just shut down infravision by overwhelming the infrared receptors. Normal vision will naturally become predominate at such times. Also be aware that larger and closer heat sources, if they are in the way, may mask smaller or more distant heat sources, even if you could normally see them at such distances if they were by themselves. For example, though you could see a halfling at 60 feet, if a man were at 30 feet and between you and the halfling, unlike normal vision where you might see the halfling around the man, chances are the halfling would be totally hidden in this scenario. This is also why very hot, low light items - like a pipe, cigar, or cigarette in your face - really obscures infravision while you smoke it. Such facts may be used to help sneak up on infrared capable sentries or guards. For example, waiting for a guard to have a cigarette before sneaking in is a good idea. Making sure they have something to smoke is an even better idea.
You will find curiosities where life is involved. For example, certain flowers reflect well in the infrared range. I do not mean they are hot, but they have NEAR infrared colors to them - not FAR infrared. Though we cannot see this - even most infravision cannot see this - bees can, and they quickly go to such lovely flowers to collect pollen - unintentionally helping to pollinate the flower.
A spider's web is nearly invisible at a distance. Surprisingly enough, the spider wishes it to be visible. A visible trap? Yes. It radiates patterns well in the infrared range, and flies can see this and - I assume like a moth to a flame or a housefly to a bright window - they head for it rather than avoid it. Nice, huh?
It has even been suggested the reason why elves are so good at finding secret doors just by passing within 10 feet of them is they have unusual thermal signatures that might be picked up while so close - even if normal light is in the area. Though the normal rule is infravision shuts down in normal light, some trace of it may remain on, particularly at very close ranges. Oh well. The mind boggles. Of course, if this is the real reason, then dwarves and other infravision capable character should have a similar chance to see secret doors.
Most subterranean areas like deep dungeons or caves are pretty much at uniform temperatures - around the mid 50's on the Fahrenheit scale - unless there are geothermal properties involved. Hot vents, lava or magma, geysers, and hot water may paint a more interesting infrared image than most areas underground. Underground running water normally tends to be very cold, however, so would stand out like shiny black surfaces amid the gray. Large open areas like entryways may be slightly cooler or warmer due to moving air, thus could be seen as a slightly different shade of gray. Little else can be seen, however, unless more heat signatures enter the picture, or things within the scene begin to move, as moving objects, even gray ones within a gray backdrop, often show up.
Moonlight is reflected sunlight. But at that distance, it does not radiate well in the infrared range, so moonlight or starlight will not spoil infravision. Similarly, starlight is not hot - not counting the close one, the sun - because of the vast interstellar distances involved. Though these do not radiate in the infrared all that well, the sky would not look black or gray, but normal vision would supersede infravision and one would see the stars and moon.
The DM will choose just how sensitive they wish infravision to be for their world. The greater the ability to differentiate between a few degrees here and there, the more detail one will see, up to and including being able to identify individuals at a distance if the DM wants this. Be advised, however, that if you make infravision this sensitive, then creatures should logically be able to follow hot footprints in the dark - say, within a half-hour of being laid down - and things like that. Also, one might be able to discern different species just by looking at them - though the DM might have to determine what different body temperatures each species normally operates at - like dogs run around 102 degrees while humans are around 98.6 - though I'd recommend most humanoid species coincidentally operate around that latter temperature, or better yet, infravision just not be sensitive enough to discern these minor differences. Also note, cold winds will wipe away such hot footprints quicker, and tracks in water or in snow or on ice do not have heat signatures since the heat was used up already - carried away by water, or used to melt the snow or ice.
In fact, you may begin to use other neat facts, like heavy drinkers are hotter than sober people, or people running a fever are hotter, and one might be able to tell who is drunk or sick - or course they can't tell which one is which, so a thief may think an apparent drunkard is an easy mark only to find he has contracted a disease for his pocket picking efforts. LOL ;-)
Cold-blooded creatures are pretty much at ambient temperatures, but their movement does heat them up a bit. If infravision is VERY sensitive, one might be able to see a cold-blooded creature sitting there, its gray outline discernible against a gray background - particularly if it recently moved off its hot rock while sunning itself and moved into its dark cave, for example. If infravision is moderately sensitive, one may only notice such things IF the creature is currently moving. If infravision isn't that sensitive - recommended - one probably won't see cold-blooded creatures at all, unless the creature is in front of a hotter or colder object.
If it isn't too sensitive, then all you may be able to discern is that some man-sized object is over there within 60 feet, but it may be your friend, an orc, a troll, or just a hot cauldron of water. Even then, in the absence of other visual or audio cues, it may be hard to judge the scale of the image. It could be cool, small, and near, or hot, large, and far. It's often too hard to tell with certainty while in the dark and one can't see the surrounding area to help judge these things. Images flying, drifting, levitating, hovering, etc. in the air are even harder to judge than those on the ground. However, if a known heat source is nearby - like your friend - then comparisons are possible. That extra heat source that just appeared next to your friend will now have something by which to judge its scale.
As a matter of game balance, the better the DM allows infravision to work, the bigger their game balance problem. Fortunately for game balance, most adventuring parties are mixed groups, and many will need visible illumination. Thus, infravision will only come into play when certain characters are alone - which still happens frequently enough. Also, many more NPC groups will be comprised entirely of infravision capable individuals - particularly racial groups, like an elven hunting party or a dwarven militia. This is probably why the home lands of races with infravision have a scary reputation amongst 'normal' vision types, since at night or in the underdark, such racial groups have fantastic advantages of choice - avoid or ambush. But I digress, again.
Water is, for the most part, opaque to infrared radiation. Infravision will not work well under water - certainly less than 1 or 2 feet, if at all. In fact, water molecules absorb this radiation so well that infravision will hardly work even in a decent FOG or up in the CLOUDS if you happen to find yourself there. I would guess anything further than 10 feet would be totally obscured.
But please do not mistake SMOKE for fog. Though smoke and fog may seem similar in the visible spectrum, they are not both opaque to infrared radiation. Infrared capable creatures can see heat sources through smoke quite well. Ask you local fireman. They use equipment to enhance their heat vision and can find people even in smoke filled rooms by seeing the heat signatures. Nice, eh?
The ability to turn invisible deserves a scientific treatment paper in and of itself. Suffice it to say that if an object is made to be invisible in the visible spectrum, this will usually include the infrared and ultraviolet spectra as well. They can still be smelled, heard, or perhaps otherwise perceived.
Unless thermally described and obvious, most magic is not a heat or a light source. Some of it that is may be dim enough or cool enough not to spoil infravision. The light from a sword may not spoil infravision, for example, but the light from a Continual Light Rock would. Naturally, spells or swords that involve flames that will actually start fires will spoil infravision. Cold flames probably will not. (Ask your DM).
This spell dampens-out energy within its area of effect in most regions of the electromagnetic spectrum. This will include infrared. This does not mean it is especially cold, really, so a hot object placed inside such an area wouldn't cool down any faster than normal. As heat radiates away, the spell swallows it, dampens it, and sends it elsewhere, but the normal rate of cooling prevails. Someone with infravision cannot see a hot object inside this area of effect. Thus, the spell will effectively hide one from infravision-capable searchers while one remains inside it. Similarly, I suspect ultravision or dark vision would be hindered.
Looking at such darkness would not suggest a cold spot either. It would probably look the same as the surrounding air. However, if it were in front of a hot wall or even a cold wall, it would stand out. Such an area is almost certainly opaque to infrared radiation - like a sheet of glass. That would mean a person on the other side of it - though not inside of it - would probably be shielded from the sight of an infravision capable creature just as a normal sighted person couldn't see them on the other side of the darkness either. Most EM - ElectroMagnetic - radiation will not pass through a Continual Darkness area of effect.
Unfortunately there is no good way to 'see' out of this field and easily maneuver around while hiding inside it. But it would be similar to being blind or in total darkness, so it can be done, particularly with those skilled in blind fighting. However, a moving field of darkness may in and of itself be overly obvious. It is often better to pretend to be a deep, immobile shadow while hiding thus.
Recall that each creature type - race - may have infravision for different reasons or in different ways. If some aspect of the justification you use for a particular creature relies on magic, then infravision of that nature may stop working while on planes of existence where the spells Continual Light or Continual Darkness do not work. (Just as it will stop working in anti magic fields or for a brief time when hit by Dispel Magic). If those light and darkness spells work on that plane, infravision should work on that plane too. Creatures native to those planes may have infravision for other reasons. However, many planes like the astral or ethereal planes probably have uniform - or near enough - temperature and would appear featureless in the infrared spectrum.
Mirrors reflect light well, including infrared. (Modern mirrors are better than polished bronze or most inferior mirrors, so take mirror quality into account). But the DM should keep the actual distances the light travels in mind. For example, an elf with a range of 60 feet on his infravision can just see his own image in the dark by looking at a full sized mirror 30 feet away. 30 feet there, 30 feet back, equals 60 feet total. Of course, if the sensitivity of infravision is low, chances are he will not know 'who' he is looking at, or even how far away 'it' is, or even what size it may be unless he knows there is a mirror 30 feet down the hall, or he has some other visual or audio cues. It could appear to be a man-sized person at the edge of one's limit, or a close halfling, or very close leprechaun, or even a giant further away than 60 feet. It's often too hard to guess distances in total darkness without other visual cues to help our brain determine the scale of the image. But if they knew from a map that the hall was 60-feet long - which is unlikely - then they might take it as a man-sized object at the end of the hall, even though the mirror would be at the 30-foot mark. Naturally, if a known heat source is nearby, then a comparison exists. More often than not, such handy items will not be available and they will not know with certainty.
And unlike a mirror's image where such detail makes it plain that's your own reflection, even this detail may be lost. A fuzzy blob is a fuzzy blob is one possibility, or maybe a vague humanoid outline can be seen. Since the mirror itself doesn't radiate its own heat, it probably wouldn't be seen. Great fun may be had with this fact.
Note: Water reflects visible light well, like a mirror, but not infrared light. Water tends to readily absorb infrared radiation, so the same trick cannot be done with reflecting pools or even vertical polished ice or something.
Always remember that infravision need not be one thing and one thing only. It may rely on several factors, but most typically will be some combination of eye size, pupil control - inadvertent, probably - cool eyes, and reflective capabilities. Each of these may have different consequences. And it may be several of them or any one of them, but generally it takes two or three such factors to get the really good infravision - 90 feet or more.
Chimneys will really stand out, like a huge blob of blurry light, a sort of puffy cloud of heat. Knowledgeable thieves may use this to hide from infravision capable seekers, sticking close to such chimneys to mask their heat signatures, thus being lost in the haze. They should remain motionless while hiding thus, however, as movement has a way of being seen.
Anything so hot it glows in the visible spectrum will probably spoil infravision if it is within the infravision's range. And naturally, normal illumination will spoil it too. A clever - and perhaps wealthy thief or magic rich thief - may drop a Continual Light rock, temporarily spoiling the infravision of his pursuers, and by the time their eyes readjust to darkness, he may be gone into the night - out of their infravision's range, anyway.
Keep in mind that sometimes infravision may reveal other unexpected things. A cold creature in front of a hot brick wall would stand out. Temporarily losing infravision due to passing through an anti magic field might suggest to an individual that he or she just passed through such a field - they might wish to check their potions, for example. Any cold objects may stand out too since they are lower in temperature - look black - compared to the room temperature's normal gray. Thus some brown mold or life energy draining undead may be apparent. Most undead, like skeletons, however, would just be ambient temperature - I assume. Even if the DM wanted skeletons to have an 'icy touch' due to their connection to the negative material plane, this could be like steel - simply drawing heat away from their victim faster than the air, though they, too, are at normal ambient temperatures.
One probably cannot read by infravision alone, unless the letters actually generate heat or were made to reflect heat and infravision is particularly sensitive. Normally, this is NOT the case.
There are lots of little animals that will register - if very close. Thankfully, if we take into account the size and distance of each source, most of them will not register even if within 'normal' infravision range - too small at that distance. Otherwise bats and mice would forever distract your character. Also always keep in mind that many animals - non-mammals and non-birds in particular - are cold-blooded and will not really register at all. And remember that just because a giant is huge, a giant isn't really hotter than a man, so he may not stand out much further away than 60 feet either - though with a greater profile, it could be up to half again that distance. And if the giant has partial cover - 50% or more - he probably won't be seen at all if outside the normal range of infravision. A hot red dragon would certainly stand out from a very long ways away, no matter what your infravision 'range' may suggest.
Friction will generate heat, so moving parts - like chariot wheels or sliding doors - will be hotter after recent use. Even if you don't allow great sensitivity, you may allow some. They just need to get closer. Perhaps 10 feet will do it; else they could simply touch the object and tell how hot it is as well.
As an option the DM may assume - if a warm object is within one-third of the infravision's maximum range - that infravision-capable creatures will have a better idea of what it is from various other cues and inputs to the brain. So for infravision of 30, 60, 90, or 120 feet, they'd know better what size the object was or perhaps even better what it was if it were within 10, 20, 30, or 40 feet respectively. But how much extra detail may be given is still up to the DM.
This skill somehow adds acuity to the senses, and though it will not work in silence fields and the like, it may add greater range to one's infrared sensitivity - if they have it already. By that I mean it may add an extra 10 feet to the 'one-third range' rule. For example, one with 60-foot infravision may normally discern more in a third of that distance - 20 feet - but with blind fighting, more cues may be available and they can discern more within 30 feet - 20 + 10. But this is optional. Ask your DM.
A big problem I wanted to avoid was the active infravision. Like active sonar - which submarines and bats use - something is actually emitted from a creature, bounces off objects, and the echo-like reflection is imaged by the creature. Countless problems will arise and thus infinite problems may be avoided if we shy away from this notion. In truth the way I have it set up here, there is no need for doing this anyway - that I can see.
This doesn't mean some creatures can't have something like this, but as a general rule, infravision doesn't work like that. And if some creature does actively emit infrared radiation to image others, those with infravision will see them coming a long, long ways off - if it's constantly on - or might notice them using it long before they are even within their normal infravision range. Such creatures would stand out to infravision capable creatures as easily as a man with a torch at night or a campfire in the distance, or ever better, a man waving around a flash light in the dark would stand out for folks with normal vision.
A better solution is simply as suggested before, with larger eyes, wider pupils, cooler eyes, and/or a more reflective quality to refocus the light, and similar reasons to account for greater ranges of infravision.
If some description on infravision, or some write up in some book of a creature with infravision suggests something contrary to what I'm saying here, do not feel obligated to follow the book unless you really need some property derived from such a write-up. Chances are it has since been superseded anyway, so it may be far better to ignore it and use this system instead. Finally, just ignore most of what any source says about infravision if you feel it is contrary to what I have here. By doing this, you will adopt a self-consistent and apparently better - as far as I can tell - workable system of infravision.
Simply stated, this is detecting things in the ultraviolet ranges. Mostly it is x-rays, cosmic rays, and ultraviolet radiation and the like. By thinking of it as simply a kind of B&W vision one may use if under the illumination of the stars, this is often good enough for game purposes. Similar reasoning used to justify infravision will in many ways apply to ultravision, but few planet-bound objects naturally radiate in this spectrum, so the ability is not nearly as useful as infravision.
Just for fun more than anything else, one may extend normal color vision by adding two new primary colors, one above violet - near ultraviolet - and one below red - near infrared. Races with such color sense will feel other races - like humans - ARE colorblind, and may even have great laughs at that race's 'poor' fashion sense. Personally, I'd avoid doing this since it will involve inventing many new shades of color and the names that go with them. Normal, everyday objects actually do radiate in the near infrared and near ultraviolet ranges, so these colors would be seen mixed with the normal primary colors and would be taken as various new shades of color. It's just that all humans would be colorblind, or color 'challenged' compared to this other race. And recall I'm red/green colorblind already and can't even deal with the colors I have. How many crayons are in that box already? You may not have this problem, however, so doing this may be fun and interesting and a creative challenge. On the other hand, it may be even more frustrating to those with color problems already.
Of course like normal colors, these new colors will also be seen by REFLECTED light, and not things generating radiation of their own accord. Thus, a light source is still needed to see these colors.
For this particularly color sensitive race, it may still take direct sunlight to see these colors. Since I have ruled Continual Light sources carry the proper EM component for photosynthesis, this would suggest under such a light source, these extra colors can be seen by members of this race as well. But other light sources may not have the right components of the spectrum for proper illumination. Torches, campfires, candles, lamps, etc. may not have what it takes to illuminate those colors. Just as colors look funny under various poor lighting conditions, so too will these new colors look funny under less than optimal illumination.
And just because this is my article, I'll tell you my favorite color. It's the way white things look under a black light, whatever you may call that. I call it electric blue ;-)
THIRD EDITION D&D
To avoid many of the problems found with some of 2e's suggestions or implications of infravision, WotC just scrapped it and decided to opt for 'night-vision' instead. Again, they shy away from giving any explanations, the 'it doesn't have to make sense' idea almost seeming to be more prevalent in some areas of 3e than I would like to have seen.
Then again, by avoiding some of the tricky issues they don't really need much in the way of further explanation. If I recall correctly, night vision, unlike cat vision, is only twice as good at collecting light - not six times. So this doesn't take huge explanations.
If you still like the idea of heat based vision, you should feel free to use it in your 3e games, though you may cut down on the ranges to bring them more in line with normal 3e ranges for night-vision and therefore not be as huge a game balance problem as giving infravision to some species for what is essentially free and with little or no drawbacks.
Dark vision, on the other hand, presents a problem. It works in total darkness. How? Magic? Psionics? Active sonar-like pinging of some carrier wave? I hope the latter most will not be the case - I hate that.
Just as a quick suggested solution, I think I'll assume that in magical space - where the fabric of space is weaker - that like a cosmic background radiation - similar to ultravision - this planar radiation is ever present and weakly interactive with normal matter. But it bounces around and will present a B&W image to those with the right receptors in their eyes, provided this isn't washed out with normal light. Normal heat will not affect dark vision. Since the carrier wave is a magical planar emission, it is prevalent in all areas - even in total darkness and away from star shine - and works everywhere except those areas where magic does not work. Thus, anti magic considerations may hinder dark vision.
Also, I think it prudent to rule dark vision would not operate in areas of magical darkness, such as within an area of effect for a Darkness spell. In fact, the spell Darkvision even suggests as much.
Under the theory that nothing is all good, dark vision may have to be saddled with some draw back for the sake of game balance. I think the most natural conclusion will be that dark vision takes time for one's eyes to adjust from normal vision to useful dark vision, thus making it impossible to jump from light to dark, back and forth without pause, and becoming too powerful. Just as normal light may have spoiled infravision, so, too, will normal light spoil dark vision. Furthermore, it takes time, perhaps minutes or even hours - ask your GM - for one's dark vision to kick in once normal light fades. At a minimum, I would suggest one minute or ten rounds, and don't think it would be out of line to even make the adjustment period hours long, or maybe even uncomfortable, perhaps explaining why deep dwarves tend to dislike coming to the surface.
Why? My fear is that, without such a provision, dark vision could and would be used to make those relying on normal vision virtually powerless when facing those equipped with dark vision. Any room instantly darkened would make those without dark vision virtually helpless, and that's just too powerful.
Of course, each time a DM tries to incorporate part of the real world into a fantasy game, he runs the risk of failing to take into account some important factor. Oddly enough, this only matters if such a factor ever comes up, or a player comes along who can see the problem. Only when you know there is a mistake does it tend to bother you. Ignorance is bliss, so to speak.
My point, gentle readers, is that if any of you can find flaws in these ideas, I'm keen to hear about them. Please write and tell me about them. Or, if you like the ideas, I'm keen to hear this too. Please write and tell me what you thought of this article. Thanks ;-)
Email Jim Your Comments (Send Praise, Critique, Complaints, Suggestions, Ideas, or Submissions).
Until then, I hope this article has been, well, illuminating, or at least has left you with a warm, fuzzy glow ;-)
Happy Gaming ;-)
© June of 2001