Sense-Based and Infravision

Strabo · 07-22-2021, 03:39 AM

Would Infravision be considered a separate sense for the purpose of Sense-Based, or should I apply Accessibility, Only Infravision, -X% to Vision-Based?

Do abilities with Vision-Based affect those who are using Infravision?

Anders · 07-22-2021, 03:59 AM

I would say it's a kind of vision. It's in the name.

Ashtagon · 07-22-2021, 04:08 AM

Aside... Standard "fantasy" infravision is a function of the same ocular orbs used for conventional vision. It turns out that snakes (the most notable RL example of infravision) have "pit organs" in what in humans would be the upper lip area. Biologically speaking, these structures are similar to what are hypothesised to be evolutionary-primitive eyes, except optimised for IR waves rather than the conventionally visible spectrum.

Unless the sense organs that relate to infravision were in a radically different location to those that handle regular vision (and maybe even then), I'd treat them as the same sense for purpose of gurps limitations and enhancements (so a gaze attack would work whether you were seeing the target normally or by using infravision).

Some things to consider:

Does the character's Infravision shut down if there is enough light to enable normal Vision (that is, would this be functionally identical to Accessibility: pitch black darkness only)?

Does the campaign have a significant number of creatures that would be genuinely invisible with Infravision (nb pretty much anything that isn't made of the same material as its background and receives heat from an external source such as the sun, or generates its own heat somehow, will be visible)?

Strabo · 07-22-2021, 05:21 AM

That sounds reasonable, thank you.

whswhs · 07-22-2021, 05:37 AM

If you want a more detailed treatment of Infravision, see GURPS Enhanced Senses, which divides it into two spectra: thermal infrared, which responds to heat emissions from things such as warm-blooded animals, and near infrared, which responds to wavelengths just below those of visible light and requires a light source. The latter would certainly be included in vision; the former is more debatable, as it's mediated by quite different organs such as pits.

Anders · 07-22-2021, 05:53 AM

It sounds whether it's part of vision or not is a 0-point feature.

Anthony · 07-22-2021, 10:32 AM

Realistically, using the same sensors for thermal IR and visible light isn't very practical (a factor of 20 difference in wavelength matters) so creatures that have non-fantastic infravision probably have more than one sensor set. Having a separate set of infrared eyes and visible light eyes seems like a perk at most (having four eyes, whether or not they're associated with separate senses, makes you slightly harder to blind). As far as sense-based goes, though, infravision and ultravision and dark vision are priced as being vision variants, not something that calls for separate countermeasures.

07-22-2021, 03:39 AM	#1
Strabo Join Date: Jun 2012	Sense-Based and Infravision Would Infravision be considered a separate sense for the purpose of Sense-Based, or should I apply Accessibility, Only Infravision, -X% to Vision-Based? Do abilities with Vision-Based affect those who are using Infravision?

07-22-2021, 03:59 AM	#2
Anders Join Date: Jan 2005 Location: Gothenburg, Sweden	Re: Sense-Based and Infravision I would say it's a kind of vision. It's in the name. __________________ “When you arise in the morning think of what a privilege it is to be alive, to think, to enjoy, to love ...” Marcus Aurelius

07-22-2021, 04:08 AM	#3
Ashtagon Join Date: Jul 2009 Location: UK	Re: Sense-Based and Infravision Aside... Standard "fantasy" infravision is a function of the same ocular orbs used for conventional vision. It turns out that snakes (the most notable RL example of infravision) have "pit organs" in what in humans would be the upper lip area. Biologically speaking, these structures are similar to what are hypothesised to be evolutionary-primitive eyes, except optimised for IR waves rather than the conventionally visible spectrum. Unless the sense organs that relate to infravision were in a radically different location to those that handle regular vision (and maybe even then), I'd treat them as the same sense for purpose of gurps limitations and enhancements (so a gaze attack would work whether you were seeing the target normally or by using infravision). Some things to consider: Does the character's Infravision shut down if there is enough light to enable normal Vision (that is, would this be functionally identical to Accessibility: pitch black darkness only)? Does the campaign have a significant number of creatures that would be genuinely invisible with Infravision (nb pretty much anything that isn't made of the same material as its background and receives heat from an external source such as the sun, or generates its own heat somehow, will be visible)? Last edited by Ashtagon; 07-22-2021 at 02:33 PM.

07-22-2021, 05:21 AM	#4
Strabo Join Date: Jun 2012	Re: Sense-Based and Infravision That sounds reasonable, thank you.

07-22-2021, 05:37 AM	#5
whswhs Join Date: Jun 2005 Location: Lawrence, KS	Re: Sense-Based and Infravision If you want a more detailed treatment of Infravision, see GURPS Enhanced Senses, which divides it into two spectra: thermal infrared, which responds to heat emissions from things such as warm-blooded animals, and near infrared, which responds to wavelengths just below those of visible light and requires a light source. The latter would certainly be included in vision; the former is more debatable, as it's mediated by quite different organs such as pits. __________________ Bill Stoddard I don't think we're in Oz any more.

07-22-2021, 05:53 AM	#6
Anders Join Date: Jan 2005 Location: Gothenburg, Sweden	Re: Sense-Based and Infravision It sounds whether it's part of vision or not is a 0-point feature. __________________ “When you arise in the morning think of what a privilege it is to be alive, to think, to enjoy, to love ...” Marcus Aurelius

07-22-2021, 10:32 AM	#7
Anthony Join Date: Feb 2005 Location: Berkeley, CA	Re: Sense-Based and Infravision Realistically, using the same sensors for thermal IR and visible light isn't very practical (a factor of 20 difference in wavelength matters) so creatures that have non-fantastic infravision probably have more than one sensor set. Having a separate set of infrared eyes and visible light eyes seems like a perk at most (having four eyes, whether or not they're associated with separate senses, makes you slightly harder to blind). As far as sense-based goes, though, infravision and ultravision and dark vision are priced as being vision variants, not something that calls for separate countermeasures. __________________ My GURPS site and Blog.