May 25, 2011

Infravision, Ultravision, and other forms of sight on the planet Ezzin

During my time running games, I always found that some of the most used but least discussed rules involved vision.  I was constantly describing to the players what their characters saw.  Yet the rules on infravision and ultravision were either vague or outright obtuse.  So, I've made some vision guidelines of my own.

I want to keep this more or less scientifically accurate (or at least plausible).  I've seen a great many explanations of infravision and ultravision on the internet, many of these descriptions are just plain wrong.  RPG's taught me a lot of things as I grew up, and may be responsible for my infatuation with science and curiosity about how things really work.  Knowing that I might one day run games for school aged kids, I do not want to misinform them (as I sometimes was) about the nature of light and vision.

Granted, most of the science here is a gross simplification, and some bits are just plain fabrication...  but I think I've got the bones of it, and the basic concepts are nailed down pretty tight.  If you notice things that could be improved upon, please let me know.  I'd be happy to make this more accurate if I can.

Normal Vision

The humans of Ezzin default to this form of sight.  The light visible to humans represents only a thin sliver of the full spectrum of light. 

Human eyes perceive light because of light sensitive receptors called cones and rods.  Rods detect the brightness, while cones detect color.  There is only one type of rod, and these are very sensitive even in dim light.  Some creatures (like dogs) have eyes with no cones, only rods, so they see only black and white.  Humans have three different types of cones, one detects blue, another green, and the third detects red.  All the colors that humans experience are from combinations of those three colors.  This rainbow of color goes in the order of lowest frequency to highest as Red, Orange, Yellow, Green, Blue, Indigo, Violet.

Most creatures need time to adjust their eyes after a sudden flash or dimming of light.  In certain situations a wisdom check may be used to determine if a character was blinking or looking away during a flash of light.  If flash blind or suddenly thrust into the dark of night, it can take 3 rounds before any details can be seen.  They can still run or attack during this time, but risk knocking over furniture or hitting allies.  Incidentally, this is why pirates sometimes wore an eyepatch over one good eye.  Then if they had to run quickly into the darkness below decks they could simply switch the patch to their other eye.  This allowed them to work below decks without having to wait for their eyes to adjust.  Handy if you're in a battle and need to find the gunpowder really fast.

I'll probably never use this chart during a game, but it might be useful as a point of reference.  It is based upon a table I found in the AD&D Wilderness Survival Guide, with some changes of my own.  If anyone knows of a better chart, please let me know.

Quibish's Visibility Chart
Unobstructed outdoor range of normal human vision in feet.
At these distances a character can identify the basic form of a man-sized creature.

                 Daylight ..... Twilight ..... Full Moon ..... Moonlight ..... Darkest Night

Clear             1600           1200              600                  300                 100
Overcast       1200             800               400                 100                   80
Light Fog        800             500               250                   70                   60
Rain/Snow      400             300               150                   50                   30
Heavy Fog      100              80                 40                    30                   20
Blizzard            50               50                 30                    10                   10
Sandstorm        40              40                 20                    10                   10

Low-Light Vision (Eyeshine)

Many animals have better night vision than humans do.  Some of this is because they have more rods in their eyes than humans.  A larger sized eye or pupil would also aid night vision.  Most often though this enhanced vision is due to an interesting adaptation of the eye possessed by many creatures (which humans lack entirely) called the tapetum lucidum.

The tapetum lucidum (Latin: "bright tapestry") is a reflective layer of tissue in the back of the eye.  Light passes over the rods and cones then reflects off of the tapetum lucidum and passes over the rods and cones a second time, thus increasing the apparent brightness seen by the individual.  Many animals have this adaptation such as, fish, sharks, owls, spiders, crocodiles, dogs, cats, cows, goats, rodents, marsupials, bats, and many other nocturnal and sea creatures.

Only the most knowledgeable sage would know the tapetum lucidum's proper name and function, most people know it simply as "Eyeshine" because of the occasionally visible effect of the light reflecting out these creatures pupils.  Eyeshine is possessed by a few sentient species on Ezzin, including the elves.  Elves can see twice as far as the distances listed on the chart above.  Elves can somehow adjust their eyes after only 1 round, instead of the usual 3 rounds that humans need after a sudden flash or extinguished light source.

It should be noted that eyeshine does not produce light, only reflects it, so it is of no use at all in dark caves and dungeons where light cannot penetrate.  Also, eyeshine gives almost no advantage when standing near a light source such as a torch or campfire because,  just like humans, the range of sight is limited by the radius of illumination provided by the artificial light.  The GM may allow characters with eyeshine to see a foot or two farther into the gloom though, allowing these PC's to react before others in the party in certain situations.  Creatures outside the circle of torchlight will sometimes be revealed by their eyeshine, those within the circle would see only a pair of shining eyes reflecting the torchlight.

Eyeshine can be of any color.  Usually creatures of the same species will all have the same color of eyeshine if all other factors are the same, but different colors of source lighting or angles of reflection can make the eyeshine appear as a different color.


Infravision allows heat to be seen.  Heat gives off light at a frequency so far below the color red that the cones in the human eye cannot detect it.  This frequency of light is called infrared.  Some creatures on Ezzin (such as the goblinoid races) have cones and rods in their eyes that are able to detect infrared.  Infravision is useful for detecting the warm bodies of prey, especially within caves and dungeons devoid of normal sources of light.  The range of this form of vision is limited because the creature constantly sees its own body heat, like a human peering through a glowing mist or fog.  A sudden burst of heat can blind infravision just as a flash of light can blind normal vision, requiring 3 rounds for the eyes to adjust.

Creatures like goblins who only possess infravision rarely venture out during the day.  Emerging from cool caves to suddenly look out at objects heated by hours of sunlight can be painfully bright, making it difficult to see detail in any object more than a few feet away.  Even once their eyes adjust, the sun is much brighter in infravision than when seen with normal vision.  Infravision is usually given a flat range of 60', 90', or 120', this is the range at which man-sized and man-temperatured objects can be seen.  Objects that are smaller and cooler will need to be closer before they are noticed.  Some very hot objects (red dragons, fireballs, lava) can be seen far beyond this range, even if only seen as big blobs of heat in the distance.

Certain magics can allow humans to see infrared.  These spells typically alter the three types of cones so that they respond to infrared rather than the normally visible frequencies of light.  Humans so effected would see the same rainbow of colors, but changes in color would represent different temperatures.  Normal vision would be lost for the duration of the spell.  Such vision might appear similar to this:

COLD [black - blue - purple - red - orange - yellow - white] HOT

Theoretically, magic users could alter their spells to reverse or mix up the order of the colors between cold and hot, but most in Ezzin use this version of the spell. 

More powerful magics can provide a very different form of infravision.  Rather than alter the three existing types of cones in the eye, these spells grow a fourth type of cone sensitive to infrared, essentially producing a new primary color that can mix with the original three.  This new color was dubbed "Ulfire" by the mage who first used such magic. Mixing ulfire with the other primary colors adds a new rainbow to be perceived by the individual.  The first use of this spell is extremely disorienting, as the individuals' mind struggles to interpret these new signals in tandem with the signals from normal vision.  Powerful headaches, nausea, and vertigo are common until repeated use allows the mind to adjust to interpreting these new signals.  Once mastered, individuals will be able to see every detail and color that they would with normal vision and be able to see variations of heat as well.  These individuals would be able to see anything visible with either type of vision, but this combination does not extend the range of infravision or limit the range of normal vision.

Some things to keep in mind while using infravison:
  • Objects hot enough that humans can see them glow visibly will be blindingly bright in infravision. 
  • Glass and water are opaque to infrared because they absorb heat so thoroughly.  Infravision does not work underwater, nothing can be seen except the surface temperature of the water.  In fact, even a mist, fog, or heavy rain could obscure heat beyond 10 feet away.
  • Smoke and dust are nearly transparent to infravision.  Infravision can be a great help when searching for people or exits while inside a burning building filled with smoke.
  • The profile of a cold creature would stand out easily if it were in front of a warm stone wall.
  • Undead are always slightly cooler than ambient temperature, constantly sucking in heat from their surroundings even in arctic conditions.  Ghosts and spirits normally invisible to humans can be seen as dark patches of cold by those with infravision.
  • Cold-blooded creatures are nearly invisible to infravision because they are usually the same temperature as their surroundings.  Even rapid movement would only give away it's basic size and position.  No details would be seen until a few rounds of continuous movement began to warm the creature.
  • Warm bodies leave warm footprints, unless walking over water, snow, or ice.  These footprints fade quickly and disappear within 2 or 3 rounds.
  • Mirrors reflect light well, including infrared.  However, even a thin layer of glass over the mirror will considerably dim the infrared light reflected, so a disk of polished metal may work better.  Also, a mirror carried around in a pack is bound to absorb some body heat over time, making the mirror itself appear to glow a bit... interfering with the reflection.
  • Visible light is invisible to the goblinoid races, just as infrared and ultraviolet are invisible to human eyes.  Because of this, goblins have no words or concept of color, but they have many words for various temperatures. 
    • Hide in Shadows is not used by creatures who see only with infravision.  The concept is simply foreign to them.  Even a creature who understands the nature of light and shadow would find it very difficult, because shadows cannot be seen with infravision.  However, such creatures would still make use of cover.
    • Hiding from creatures with infravision can be very difficult.  Shadows and colored camouflage will be of no help.  Covering yourself with cold mud or slime might disguise you until it is warmed by your body heat.  Ten feet of thick fog could hide your heat.  Going underwater would work very well... until you had to breathe.  Hiding behind large rocks or trees blocks heat effectively, although eventually a fire or warm body would warm the air nearby producing a telltale glow, unless dissipated by wind.  It may even be possible to hide in what would normally be plain sight by standing near a large source of heat such as a chimney, forge, or a large creature.  It's possible that the air itself might even hide a person if it were very close to 98.6°.  A spell like Invisibility to Infravision, or a magic item such as an "Evercold Blanket" could prove useful.


    Above the color violet are shorter, more energetic wavelengths of light that are invisible to the human eye.  This sliver of the light spectrum between violet and x-ray is called "Ultraviolet" or "UV".  Ultravision allows creatures to see ultraviolet light.  UV is found in sunlight (6.8% of sunlight is UV, 54.3% infrared, 38.9% visible to humans), electric arcs (lightning), and specialized black lights.

    Creatures on Ezzin who only see in ultravision are basically screwed.  The atmosphere of an Earth-like planet blocks most of the UV from its sun, electric arcs aren't common enough to be a viable light source, and black lights aren't readily available.  Fire does NOT produce UV light.  Creatures who only see UV would (I think) quickly be wiped out through natural selection.  Therefore, most creatures on Ezzin with Ultravision also have an additional form of vision AND produce their own bio-luminescent UV light source.

    Let's take a closer look at the Dwarves, shall we?

    The Dwarves of Ezzin have evolved antennae which can glow like black lights.  This output of light is controlled consciously and has two basic settings when in use.  The first is totally invisible to human eyes, the second can be seen by humans as a faint blue/white glow in the tips of their antennae, almost equal to the brightness of a firefly, enough to see from a distance on a dark night but far less bright than a candle.  To the Dwarves both of these settings give off UV light which allows them to see a 60' radius.  This expenditure of energy is not negligible and may account for the Dwarves renowned appetite, and fondness for alcohol.  Dwarves cannot maintain this glow for more than a few hours at a time, and must snack and drink throughout the day if they wish to produce the glow for extended periods without becoming fatigued.

    Dwarven eyes have four types of cones.  Three types see visible light just as humans do, these are sensitive to red, green, and blue.  The fourth type is sensitive to a band of UV light, the Dwarves call this color "Jale".  Thus, the dwarves see four primary colors which can all mix together, as opposed to the three seen by humans.  Dwarves see many more colors in a rainbow than humans can.  Because of this dwarves have little respect for human artistry, they see imperfections and color clashes where humans do not, likewise dwarven color schemes can seem ugly to human eyes.

    There are rumors that the Dwarves have developed a secret language based upon the flashing of their antennae.  It is said that they can communicate silently over great distances by interpreting the number and length of their flashes.  Much is suspected, but little is known for certain... the Dwarves do not speak of such things with outsiders.

    One odd side effect of this UV light production is fluorescence.  Some chemicals in minerals, plants, or animals will absorb some the higher energy UV light produced by the Dwarves' antennae, and reflect or emit lower energy light that is visible to the human eye.  Thus, sometimes when dwarves use their antennae, humans will see certain minerals, plants, or animals near the Dwarves begin to glow.  The dwarves can also see these effects.  Dwarven "magic" is based mostly upon superstition regarding such fluorescent effects (which may explain why you don't see many effective dwarven magic-users).  Fluorescent minerals are highly valued in dwarf society, treated as gemstones (gemstones often fluoresce).  These minerals might be used as construction materials, ground up to be used in inks, and for many other purposes.  The "magical" properties of these minerals are usually based upon the colors that they fluoresce.  Minerals than glow Blue/White under the antennae glow are usually considered protective or lucky, but keep in mind that dwarves often see colors a bit differently than other species.

    If you thought Dwarves were sensitive about their beards, you won't believe the care and attention they give to their antennae.  If severed, Dwarf antennae will grow back after 2d4 weeks.  Healing spells will only close such wounds and stop bleeding, regeneration magic however can drastically reduce that time.


    Darkvision looks essentially the same as normal vision, except that it displays only shades of black and white, and just so happens to work in total darkness.  Many games use darkvision to replace infravision and ultravision because it is easier to imagine and has far fewer idiosyncrasies.  Most sane GM's are wise to embrace it.

    I, however, am not especially wise nor sane.  I like all the interesting quirks provided by strange types of vision.  I think it's fun to watch the players think outside the box and try to trick their opponents, and infravision/ultravision provide more opportunities for that sort of thing.  I still plan to use darkvision for a few underground species though, because variety is nice, and the same tricks shouldn't work against everything.

    Aura Perception

    This ability belongs in this list least of all, those who possess it are called "Seer".  Aura perception is more of a psychic ability than a form of vision, but the minds of those who can perceive it often overlay such information within the signals from the eyes.  Yet, even if blinded, those with the gift will still be able to "see" the magic of the Dreaming Gods around them.  Some seers can also "see" or feel magic that is behind them, out of their line of sight, but they are at a loss to describe how.

    Some magical effects can be seen by anyone, light spells or fire magic especially.  A seer sees... differently, the underlying forces are exposed.  A seer can see spells as they are being cast, rather than just the effect at the end.  Even the portals of the Dreaming Gods can be seen, though they sometimes appear without warning.

    To see magic is a terrible thing.

    Magic-users wear their prepared spells like a swirling fog.  When cast, magic does not flow like water or gust like wind.  Magic slithers and darts, it is very much alive.  At times it even seems aware, staring back at those who watch it.  It often looks much like a snake, slithering toward its target, and then striking like lightning at the completion of the casting.

    Some seers can recognize the types of magic from the colors that they perceive, but such skill takes much practice.  Even then, some peculiar spells might be seen in false or conflicting colors.  Some of the most renowned seers claim that there are eight colors of magic, one for each school.  The seven colors of the rainbow, plus an eighth color that some call Octarine

    It should be noted that the rune magic of the Azhuloughmahni cannot be seen by any seer, or revealed by any known magic.  It is separate, different than the magic of the Dreaming Gods.  It can only be revealed by looking for the runes themselves, which must be drawn or carved upon the enchanted object or person.

    Invisibility, Darkness, and other Magical Effects

    There are many sorts of low level specific invisibility.  Invisibility to Undead, Invisibility to Infravision, Invisibility to Ultravision, just to name a few.  The generalized spell "Invisibility" causes any frequency of light to pass directly through a subject, rendering them invisible to all forms of vision (though very sensitive seers might see the aura of the magic).

    The spell "Darkness" does just the opposite.  No frequency of light can penetrate a darkness spell, so no form of vision can see inside.

    Some powerful magics were created in ages past by a magic-user known as Three-Eyed Gheairgo.  It is said that with one eye, he saw as goblins do, with the second he saw as the dwarves, and the third eye that he grew for himself could see the Dreaming Gods themselves.  Some say that it was Gheairgo who named the colors Ulfire, Jale, and Octarine.  He had many apprentices, and he researched and attempted to cast spells upon them so that they could also see all of these things.  None survived.  Some wept tears of blood and lived long enough to say things like "It's so beautiful" or "My Gods, it's full of stars", but none lived longer than a few minutes after the casting.  Three-Eyed Gheairgo went into seclusion after the death of his fifth apprentice, ROY G. BIV.  There are many tales of his demise, but who can say which is the truth?


    Well, this took longer than I intended.  Perhaps I should have split this into a few different posts, but it's finished now so it might as well stand together.  I'd be lying if I didn't admit that I was highly influenced by webpages about the merits and use of infravision, especially the one at General Starlight.  Others who seem to despise infravision also helped in a way.  Nothing pushes me to try harder than people telling me that something cannot be done, such as rants like this.

    I would be remiss not to mention that I borrowed "Ulfire" and "Jale" from  "A Voyage to Arcturus" by David Lindsay.  "Just as blue is delicate and mysterious, yellow clear and unsubtle, and red sanguine and passionate, so he felt ulfire to be wild and painful [and] jale [to be] dreamlike, feverish, and voluptuous."

    I borrowed the color "Octarine" from Terry Pratchett's Discworld series.  A color which only wizards can see.  It is described as being approximately a sort of fluorescent yellowish-greenish-purple', which may be based on the splashes of afterimage one sees after staring into a bright light.

    I thank you,  my readers.  I hope you had fun.  I appreciate your time, and welcome any comments.


    1. Did you know I actually have a few more vision modes than this available in Synapse? Check it out.

    2. Cool beans.

      I'd been meaning to take a look at your games. I'm planning for my campaign to have portals allowing the characters to travel into a lot of different game systems, and free games fit my budget nicely.

      I really like Synapse's build-your-own-species rules, even though point buy systems aren't usually my bag. I also rather like that you give short descriptions of the types of vision and leave it to the GM to determine the rest. Any GM who wants detailed complex vision guidelines are just going to houserule their own anyway, like I just did.

      I did forget to include compound eyes or bug-o-vision. I was just planning to use low-light vision mostly. They'd have a huge peripheral range, see movement very well, and see details poorly.

      Echolocation I'm planning to describe in a later post (much later) along with Tremorsense (the spice must flow), Superscent (pheromones), Taste-o-vision (Gentle Tongue-Tongue, he weeps for he has but one small tongue with which to taste the world), and some other oddities like how sharks can find stressed animals by detecting the electric impulses in their thrashing muscles.

      It's a weird world out there.

      Synapse mentions ultravision seeing very well at night, and insects seeing infrared. I've seen those mentioned in other systems also, but I've had trouble finding any science to back it up. Do you guys know something I don't?

    3. It seems counter-intuitive, since the UV light comes from the Sun, but during most of the moon's cycle it reflects a significant amount of UV light and starlight is powerful on UV as well. Most birds have UV receptors and they can see well at night as a result (they also use UV markers for mating purposes).

    4. Best account of fantasy vision I've ever read! I love the scientifically plausible explanations! Gary Gygax would be proud.

    5. Wow, thank you for the kind words Jack.