Kilojoules as Light

[LoganSaj]

For those of us non-electric engineers, how do you convert the Create (Light) into effect?

[DrTemp]

Well, the same way as everything else, as written on page M180: the Draw Power spells equals 10MWs (10MJ) with 28 FP per second.

Note that, of course, actual bodily energy consumption for casting a spell normally is way below that. One FP will probably be more in the KJ range than in the MJ range (something like 70 KJ, if it requires to regenerate for 10 minutes after spending one FP?), but Magic seems to be able to somehow multiply the energy if it comes from living beings.

[LoganSaj]

So ... how would that convert into light "brightness"?

[Bruno]

Originally Posted by DrTemp

Well, the same way as everything else, as written on page M180: the Draw Power spells equals 10MWs (10MJ) with 28 FP per second.

I think you've mis-understood, DrTemp. LoganSaj is talking about the new advantage Create from the Powers book. :D

LoganSaj, off the top of my head, I'd allow you to cancel out one level of light penalties with one level of Create, but I have no idea if that's fair.

[Bruno]

Ok, went back and re-read Create. It gives amount of energy created in kiloJoules, and caps energy output to 15 kW to prevent things from getting too dangerous.

I had a peek at the Luminous efficacy article on wikipedia. An ideal white light produces 242.5 lumens per watt. That means the brightest light you can create is 15,000 x 242.5 lumens or 3637500 lumens. Which is a WHOLE LOT of lumens.

Essentially your real restriction is how long your created light can last. How long you can sustain maximum brightness (in seconds) is determined by dividing your kJ output by 15 kW. A level one Create, producing 1000 kJ, could sustain your 3637500 lm light for 1000/15 = 66 seconds of OMFGBRIGHT light. You can make it last longer if you create a dimmer light.

In an effort to convert this to candela, which are a saner unit, I'm going to assume you create a point source that illuminates the entire region around it, with no occlusion. Under these conditions, convert lumens convert to candela by dividing by 4(pi). So you're creating a 289463 candela point light source.

Very roughly, you are producing the light of 289463 candles from a single point.

Ow.

[laserdog]

I've had two topics on the subject, which may or may not help ya:

This one has the math heavy bits:
http://forums.sjgames.com/showthread.php?t=11365

This one has a less math intensive system that still realistically represents that it's energy (e.g. directional sources are brighter than radiant sources):
http://forums.sjgames.com/showpost.p...5&postcount=13

However, yesterday, after reading the "Getting Tricky" section on the Control ability in Powers, I really am more of Bruno's mind on this (to keep it more centered on the bonuses given rather than the electromagnetic math).

Hope that helps.

[Bruno]

For comparison, a 120 watt incandescent light bulb produces roughly 1800 lumens.

[laserdog]

Originally Posted by Bruno

For comparison, a 120 watt incandescent light bulb produces roughly 1800 lumens.

Modern light bulbs are pretty inefficient btw. About 117 of those watts are going towards creating heat, rather than actual visible light.

But now I'm trying to turn this into the exact sort of engineering debate the poster didn't want...

Ignore me. =)

[Bruno]

Considering that Powers explicitly says that the energy is released slowly enough to not cause significant damage (the guideline is 1 hp of damage per level and I think that OMGWTF concentrated light source I worked out in my previous source counts as a little too intense), I think the better route would be to work out something rational based on either canceling out all light penalties evenly in a volume measured in hexes (which are usually 12' tall when it matters) and figure out the radius of that area based on your level, or work out a sliding scale of point-light-sources that last for a reeeeely long time.

The first one (with an area) will produce a directionless, uniform light source, as if the air itself were sort of glowing. Inside the area there will be no shadows and there will be pretty much no hiding from the light. This produces strange things like having the inside of your eyelids be lit up, the inside of closed boxes, etc. This is primitive video game style light, back before 3d accelerators and fancy lighting effects. It will look really really strange.

The second one (with a point source) will produce light like a far-more-normal object, as if you'd cast Continual Light on something.

For the first one, we start getting into candela/(square meter).

For the second one you'd have to find the candela of various things and do a little math to adjust the duration. Duration is going to go up dramatically as you ramp down the light intensity.

[Bruno]

Originally Posted by laserdog

Modern light bulbs are pretty inefficient btw. About 117 of those watts are going towards creating heat, rather than actual visible light.

But now I'm trying to turn this into the exact sort of engineering debate the poster didn't want...

Ignore me. =)

I was only mentioning the wattage as most people can visualize how bright a 120 watt bulb is :D