IR Perception Question

[Gemphyre]

An interesting question was raised by a new player in my Supers campaign. Luckily, it was not during combat, so I did not have to make a snap decision. However, I would like some input from others before it becomes a problem.

 

The character in question has Sight Group IR perception, no other special modifiers to this. During "normal" circumstances, this is not a problem. She can see heat sources in the dark, etc. However, in reference to a recent battle where she was introduced, she raises an interesting question/argument.

 

The battle was with GRAB, and the question deals with Hummingbird when she is shrunk. Assuming that ambient temperature is normal, and given that there are most living beings are significantly warmer than their surroundings (20-30 deg. F at least), this should make them glow significantly in the IR spectrum. For something as small as HB, she should show up as a bright red ball. Even more so if it is cold out. Therefore, she should be easier to see, and thus to hit either HTH or at range.

 

Possible ruling for normal conditions. If there are no heat sources or heat shields between the character and the target, the Perception Penalty is divided by 2, round down. And if the Perception roll is made, the DCV penalty from size is divided by 2, rounded down when shrunk, and applied BEFORE any maneuvers. This only applies to shrunk/small targets, and has no effect on normal sized targets and no effect on Range Modifiers.

 

For cold weather/environment, there can an even further reduction of the Perception penalty because of the greater difference in heat from the source and the environment (glows bigger and brighter). Perhaps a division by 3 or 4 for extreme cases. For a shrunk character with fire/heat powers, the same thing can be done normally. The division of the DCV penalty probably should not be changed in any case.

 

I am looking for opinions and suggestions please.

 

Mark Sebree

Gemphyhre

[Checkmate]

Re: IR Perception Question

 

Well your first problem is that IR doesn't actually detect heat, it detects light in the IR spectrum. It is exactly like UV Vision just using a different wavelength. What your character wanted was Thermal Vision.

 

Now going on the assumption that we're now talking about Thermal Vision I'll answer your question: While someone with shriking does get a bonus to preception modifiers made against them, this isn't where the the bonus to HtH or Ranged attacks comes from. I can see a needle from 20' away, doesn't mean I can hit it with a rock or bullet. Now I would negate the perception bonus for someone with Thermal Vision if the the ambient temp was significantly lower, but not the DCV modifier.

[Gemphyre]

Re: IR Perception Question

 

> Well your first problem is that IR doesn't actually detect heat, it detects

> light in the IR spectrum.

 

That is what heat is. Light in the IR spectrum. High School physics and chemistry. All bodies above Absolute Zero give off heat, and thus radiate in the IR spectrum.

 

However, since all bodies radiate, it is differences in the amount of heat they are radiating relative to the surrounding environment that make them visible. If there is another similar heat source between the viewer and the target, the target disappears. Also, if the ambient temp is close to the target's surface temp, it's "glow" is washed out because everything else in the area is radiating the same amount in near the same wavelengths.

 

This is why most real world thermal imaging and perception devices are cryogenically cooled, to increase the thermal differential, and make the heat source stand out more.

 

> It is exactly like UV Vision just using a different

> wavelength.

 

Except that most targets do not radiate in the UV range, as they do in the IR range.

 

> What your character wanted was Thermal Vision.

 

What is the difference between IR Perception and "Thermal Vision"? Specifics. After all, IR perception *IS* thermal vision. You are seeing heat (the literal meaning of "thermal vision").

 

>

> Now going on the assumption that we're now talking about Thermal

> Vision I'll answer your question: While someone with shriking does get

> a bonus to preception modifiers made against them, this isn't where

> the the bonus to HtH or Ranged attacks comes from. I can see a needle

> from 20' away, doesn't mean I can hit it with a rock or bullet. Now I

> would negate the perception bonus for someone with Thermal Vision if

> the the ambient temp was significantly lower, but not the DCV modifier.

 

If you look back at my original post, I said that range modifiers are not affected by this. The idea is that a person with IR perception would have an easier time picking out a small target that is warmer than its surroundings than normal. If you can see a target, you have a better chance of hitting it. That is why not all of the DCV from shrinking is negated, only a portion of it.

 

Gemphyre

[Trebuchet]

Re: IR Perception Question

 

I would give a moderate bonus to PER (+2 or +3) for a warmer object in a cool background, but no bonus to hit. Something REALLY hot might get significantly larger bonuses towards being detected.

 

In our campaign we've allowed PCs with IR Vision to see basic shapes through thin non-insulating walls (such as tents or curtains).

[ghost-angel]

Re: IR Perception Question

 

Easy to Spot is not the same as Easy To Hit.

 

You're still trying to hit a very small object, a very small moving object no less.

 

Humming Bird will have difficulties sneaking past the character, but the character doesn't negate any DCV bonuses or OCV penalties.

 

--

On another note: There is a difference between Thermal Imaging and Infrared Imaging - they do use different technologies.

 

Also, what we see as Infraread in things like IR/Nightvision goggles are generally False Color images.

 

And note that Infrared is not the only source of "heat" in an object. Thermal Radiation occurs across the entire spectrum, it is not limited to the IR portion.

 

For game purposes, unless you're playing Science Team Hero, I'd wouldn't worry about the difference much.

[Gemphyre]

Re: IR Perception Question

 

> Easy to Spot is not the same as Easy To Hit.

>

> You're still trying to hit a very small object, a very small moving

> object no less.

>

 

You have a point here.

 

> Humming Bird will have difficulties sneaking past the character, but

> the character doesn't negate any DCV bonuses or OCV penalties.

 

More than you suspect. IR Perception isn't the only enhanced sense the character has. :-)

 

This is why I am asking the question BEFORE it becomes an issue. If I have the answers, as well as the logic behind it, ready for when the situation arises, the rules seem less off-the-cuff and are less likely to provoke discussion.

 

--

> On another note: There is a difference between Thermal Imaging

> and Infrared Imaging - they do use different technologies.

>

> Also, what we see as Infraread in things like IR/Nightvision goggles

> are generally False Color images.

 

I am actually well aware of this, since I deal with it on a professional basis.

 

> And note that Infrared is not the only source of "heat" in an object.

> Thermal Radiation occurs across the entire spectrum, it is not limited

> to the IR portion.

 

However, the major portion of the heat signature of objects likely to be encountered on Earth is in the IR spectrum. That is why the IR spectrum is associated with heat in common parlance.

 

>

> For game purposes, unless you're playing Science Team Hero, I'd

> wouldn't worry about the difference much.

 

My question came from how Checkmate was differentiating Thermal Vision from IR Perception. I honestly have no idea what he meant and how they were supposed to be different. especially in game terms. He did not define what the differences were supposed to be. And then he proceeded to answer my question using a power/ability that was not clearly defined except for saying that it was different from the power I was asking about.

 

Without defined differences, I see them as being essentially the same. IR Perception sees heat as defined by the rules and by logic, and since "thermal" refers to heat, that makes "thermal vision" mean "heat vision", or seeing heat, which is what IR perception is.

 

Gemphyre

[ghost-angel]

Re: IR Perception Question

 

> Easy to Spot is not the same as Easy To Hit.

>

> You're still trying to hit a very small object, a very small moving

> object no less.

>

 

You have a point here.

 

> Humming Bird will have difficulties sneaking past the character, but

> the character doesn't negate any DCV bonuses or OCV penalties.

 

More than you suspect. IR Perception isn't the only enhanced sense the character has. :-)

 

This is why I am asking the question BEFORE it becomes an issue. If I have the answers, as well as the logic behind it, ready for when the situation arises, the rules seem less off-the-cuff and are less likely to provoke discussion.

 

About the only concession I would give the character is the lack of a need to make a perception roll to find Humming Bird.

 

After that it's Mechanics As Normal.

[Checkmate]

Re: IR Perception Question

 

If I have managed to offend you in some way, please let me know. That said:

 

That is what heat is. Light in the IR spectrum. High School physics and chemistry. All bodies above Absolute Zero give off heat, and thus radiate in the IR spectrum.

 

However, since all bodies radiate, it is differences in the amount of heat they are radiating relative to the surrounding environment that make them visible. If there is another similar heat source between the viewer and the target, the target disappears. Also, if the ambient temp is close to the target's surface temp, it's "glow" is washed out because everything else in the area is radiating the same amount in near the same wavelengths.

 

This is why most real world thermal imaging and perception devices are cryogenically cooled, to increase the thermal differential, and make the heat source stand out more.

Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. Infrared light has a range of wavelengths, just like visible light has wavelengths that range from red light to violet. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. The "far infrared" is what we in the military call Thermal Imaging, and it's not used very often so I tend to forget it's still technically IR. Most military IR goggles look a lot like UV goggles when you look through them. So I apologize for that.

 

If you look back at my original post, I said that range modifiers are not affected by this. The idea is that a person with IR perception would have an easier time picking out a small target that is warmer than its surroundings than normal. If you can see a target, you have a better chance of hitting it. That is why not all of the DCV from shrinking is negated, only a portion of it.

 

Gemphyre

And if you look back at my post, no where in it did I mention range modifiers, but I did mention the DCV modifiers. The point of my post and my example with the pin is exactly what ghost-angle said.

[GAZZA]

Re: IR Perception Question

 

I believe the RAW give the Shrinking PER bonus to all forms of perception, that is, she'd be harder to spot with IR because she's tiny (just like her tiny mind makes her harder to spot with Mental Awareness, she has a tiny Radar image, and so on).

 

Now, one could certainly argue that the contrast would make her size work against her here - on the other hand, though, perhaps there's a sort of "aliasing pixelization" technique working in her favour (that is, although she's a warm dot contrasting against a cool background, the IR eyes pick up a "mostly cold" area and perhaps have a "blind spot"). I'd go with that for the sake of simplicity (ie basically I'm inventing some semi-plausible explanation to let the RAW stand); YMMV.

[Lord Liaden]

Re: IR Perception Question

 

I'm not sure that a shrunk Hummingbird would look like a bright red ball in the IR spectrum. At her minimum size I'd say more like a bright red speck, like the tip of a small flashlight. Such a light may be obvious at a distance, but the small surface area that's actually emitting light is no larger because it's bright, and thus should be no easier to actually hit.

 

I can also think of a number of conditions under which Hummingbird would not particularly stand out from her surroundings in the IR spectrum: amidst a crowd of people with the same body temperature, on a warm sunny day when the pavement and building walls have been heated, in the vicinity of cars or other running machinery that throw off heat while operating.

[Outsider]

Re: IR Perception Question

 

In the rulebook under perception roll modifiers, a trying to spot a 'high contrast object' is a +5 modifier. Being a source of heat in an otherwise low temperature environment would count as that for someone using IR vision. Same as being a guy wearing a strobe light on his helmet for someone using normal vision.

[GAZZA]

Re: IR Perception Question

 

I dunno, that sounds dangerously close to a free +5 PER modifier for IR (as this would come up fairly often, I should think).

[Outsider]

Re: IR Perception Question

 

How much of a bonus would you give someone to see a man who is carrying a lit flashlight in the dark? Being a heat source in a cool environment is the same thing to someone with IR vision.

 

If +5 is higher than you want, declare +5 to be what something just short of hot enough to emit in the visible spectrum (ie almost glowing red) contrasts as, and declare body temperature vs a cool night to be only +2 or somesuch.

 

My point is that the rule for handling this is (buried!) in the rules already, as far as I can tell.

[Gemphyre]

Re: IR Perception Question

 

I dunno' date=' that sounds dangerously close to a free +5 PER modifier for IR (as this would come up fairly often, I should think).[/quote']

 

Not that often, I would think. Most items would wash out or block the IR. Common window glass does this already. And there would be no modifier for normal sized persons already in a lighted situation.

 

The situation as I originally stated it only applied to shrunken characters, and any modifiers would assume clear LOS, and before other modifiers. That is why I was considering making it dependent on levels of Shrinking rather than a fixed amount. However, reading people's comments makes it clear that a fixed cap on the bonus would also be a good idea.

 

Therefore, here is a modified suggestion.

For a shrunken character, in normal combat situations and assuming that the character has no active fire/heat powers or elevated temperature, a person with IR Perception gets a bonus to their Perception Roll of 1/2 the number of levels of Shrinking, to a maximum of +3, rounded up, in order to counter the Perception penalty that Shrinking imposes. This bonus is applied before range modifiers and other adjustments. Hot environments (over 90 deg F) can reduce or eliminate this bonus, and cold environments can increase it, as can active fire/heat or ice/cold powers. The maximum bonus should not be above +5 to the Perception Roll in any case after all factors are included. Interposing people and materials can also affect the bonus, usually lowering it quickly to zero, due to other heat signatures drowning out the one behind it or materials blocking or absorbing it.

 

This has no effect on the DCV bonus from shrinking, only the perception penalty.

 

 

Gemphyre

[Ockham's Spoon]

Re: IR Perception Question

 

Let me first ask this: does IR vision get a bonus for a normal sized person because of their heat signature under normally lit conditions? No. So should you get a bonus on a shrunken person under normally lit conditions? No.

 

Now if you are in the dark, your normal vision doesn't work, but your IR vision allows you to function "normally". But do you get an extra bonus for seeing in the dark? No.

 

What you really need to ask are what are the other modifiers. For normal vision, if you have a high contrast situation (white object against a black background) you might get a bonus. Similarly for IR vision if you might get a bonus for high contrast, a "hot" object against a "cold" background. In this case it is up to the GM to decide if the circumstances merit a PER bonus (or penalty) or not.

 

On a related topic, I have often given characters +1 to their PER roll for each enhanced sense they have that applies. The reasoning here is that you are more likely to have at least one sense that has a favorable high contrast the more senses you have. That puts kind of a mechanic to it without me having to think what the scene might look like for any given sense, which is hard enough to get my mind around when we aren't in the middle of combat.

 

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