Tuesday 30 January 2018

Why Infravision Sucks

Infravision, as it's described in AD&D and the like, is just a terrible idea, conceptually speaking.

For a start, let's look at its limited range. Most creatures with infravision can see with it out to 60', but why? Why does it stop? If it's a sense that distinguishes temperature gradients as a visual signal, then a man (or a dog, or a Ravenous Bugblatter Beast) standing at 50' and one standing at 70' should be pretty much equally visible.

The range limitation only makes sense — barely — if the sense is based on receiving a reflected signal from some sort of active emitter, like early night-vision equipment that used an infrared lamp and an IR-sensitive receiver. But where does the IR beam come from, in a creature with infravision? From its eyes? In which case, what's it using to see with? If it is coming from the eyes, then they'd be glowing like flashlights to any other creature with infravision, and they'd blind each other if they looked each other in the face.

Which brings us to another point: warm-blooded creatures are warm. If such a creature had IR receptors in its eyes, those receptors would be surrounded by a body-temperature bath. It would be like trying to see clearly with a light-bulb right next to your eyes — it might not blind you completely, but it will certainly impair your visual acuity.

For infravision to be sensitive enough to be able to distinguish an individual's facial features, the hot eye-bath would be crippling, making the whole sense mostly useless. Assuming the sense existed at all, at best it would be able to make out gross forms, maybe silhouettes, and if you were trying to navigate an area of a more or less constant ambient temperature, you'd be walking into walls and tripping over furniture a lot.

I don't expect D&D to strictly adhere to the laws of physics, but if it's going to pay lip-service to them, it could at least try not to be so blatantly egregious in its hand-waving.

Later editions of the game dumped infravision completely and just used a pretty-much undefined, maybe magical, thing called Darkvision. I don't really recall ever reading anything that tried to explain how it works at all, which is, I think, an improvement over the clusterfuck that is D&D infravision.

Note: I'm doing away with infravision in my AD&D campaign. Nobody gets it. I'll give those creatures that currently have it an enhanced ability to see in dim light, but they'll see like a cat, not like an Advanced Optics Night Vision Apparatus. I'll keep the Infravision spell though, because that's a magical effect and requires no more handwaving than saying "it's magic". 
Also: Why the hell should halflings have infravision anyway? They're basically meant to be short fat jolly rural rustic English peasants. Screw them.

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