infravision no more

published : 2014.12.14

The "infravision" of Dungeons and Dragons is hopelessly broken. In the game, various humanoid species can see in complete darkness through what is alternately written up as one of:

  1. a magical ability to see reflected short-wave infra-red light that is very similar to the color spectrum we humans enjoy
  2. natural sensitivity to emitted long-wave (or thermal) infra-red of the sort that allows you to distinguish something from its surrounds by its temperature


There are some real problems with both. I'm not going to go into a lengthy scientific analysis of the sort that could easily eliminate certain large, fire-breathing, flying, and titular reptiles from the game. I'll keep this short and explain why I've eliminated the whole idea from the game.

short-wave infra-red is reflected light

Night vision devices help modern humans see things in the dark. The point of these devices is that they help us see reflected light (either from the Sun or from an artificial source) that we can't normally see. They help us "see in the dark" by showing us what's available in the much broader spectrum of reflected light that we normally just don't see.

Even if we could somehow overcome the feeble nature of this form of reflected light (it's only 1/10th to 1/5th the strength of visible light) these devices would be useless in a pitch-black dungeon setting three hundred meters under the surface of the Earth. There is simply no source for this light.

thermal infra-red wouldn't work

I'll detour into over-analysis to start with: a problem with long-wave (thermal) light isn't sensible by anything remotely like a human eye. At 1/100th the strength of visible light, much thermal infra-red light is absorbed by the lenses in our eyes (which themselves are emitting this form of light). I wouldn't mind if certain species were allowed to see this light because of magic - for instance, we accept that the dwarven race was supposedly sculpted by a god out of magma, and that there are species of monster from the future (Mind-flayers), a previous universe (aboleth), elemental and negative planes of existence, hells and heavens of every imaginable sort, the Faerie realm, and who knows what else.

So having living things that see long-wave (thermal) infra-red is fine with me.

But what are they seeing? The long-wave infra-red light emitted by rocks, trees, water, humans, metal, etc reflects the temperature of the very outside sub-millimeter, not its internal warmth. Half the things that go bump in the dark of a dungeon are already dead. Or are cold-blooded. Or are magical and have bizarre temperatures (e.g. fire beetles, frost giants, etc). Some are invisible, walking in the walls or another plane, are inhabiting another creature, or are wrapped up in cloth or armor or scales or fur. Others simply wield torches to see. In other places, there is abundant torch light. In none of these cases would an encountered creature be sensible, as it would be damn hard to understand what you are seeing.

mysterious mammal
Ah yes, I'm being approached by a .. cat?

This is made worse by the inability to see distinguishing surface details in long-wave infra-red light. You just see the value of the temperature, not lines and shapes. In the sample below, it's clear that we're seeing a human. But what's going on with his lower face? Is that a beard? Is his face partially covered? Is he perhaps holding a camera or a rifle? Or is he drinking something cold? And just what is happening in the background?

mysterious man in infra-red
Just what's going on here?

Humans wreck everything

The worst aspect is that humans don't have any kind of "infravision" at all. So if the rest of the party is making do with their "infravision", are they leading along one or more blind humans?

Or does the torch-weilding human wreck everything for the other races by drowning everything in "hot", flickering light?

Game play

I've decided to get rid of it. I don't mind if non-humans have short-wave infra-red sight capability where there is natural light (e.g. in twilight, or by the light of the moon and stars). But since neither short- or long-wave infra-red vision really makes the game more interesting, and in fact adds distortions and problems, I'm scrapping them.

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rand()m quote

It is not necessary to change. Survival is not mandatory.

—W. Edwards Deming