Size Attribute?

[samloyal23]

How do you derive height and weight from Size or determine Size for objects you have measurements for? This attribute seems too abstract, I cannot visualize it...

[fmitchell]

How do you derive height and weight from Size or determine Size for objects you have measurements for? This attribute seems too abstract, I cannot visualize it...

There's a couple of tables in the Big Gold Book, on p 26 (for characters) and p 296 (for inanimate objects) that translate SIZ into height and weight ranges.

That said, it is abstract, intentionally so; it's less about precise height and weight and more about leverage and inertia. Think of it this way: a SIZ of X means that a STR of X has a 50/50 chance of shifting it.

[ORtrail]

This has been the subject of fairly recent discussion. You could look at these threads:

Help me accept Size as a Statistic

The Bigger the Hole, the Harder to Get Through?

[tzunder]

RQ6 has alternative and quite extensive discussions about SIZ and it's real world measurement.

My advice, as usual, based on 33 years gaming, is 'don't sweat it'

[threedeesix]

Its easiest if you ignore height while determining an existing character or creature and just base SIZ on weight.

Weight it a constant with SIZ, height varies by type of creature. For example, a 15 foot long snake and a 15 foot tall giant should NOT have the same SIZ, one is obviously harder to knockback, harder to lift, harder to hit, etc. But a 600 pound snake and a 600 pound giant should have the same SIZ.

With SIZ, weight is constant. It just makes more sense that way.

I see this come up a lot on these forums and decided for Classic Fantasy 2nd edition I would try to clear it up somewhat. What I did is create a table that showed how much each SIZ equals in pounds. And then derived a separate table that determines height by SIZ according to race. That way you can have a SIZ 10 dwarf and a SIZ 10 human both weigh the same, but the dwarf be only 4'8" tall while the human is 5'6".

For anything other than a player character, SIZ equals weight and height simply doesn't matter.

Obviously every experienced BRP player has their own way of handling SIZ, but that's how I chose to look at it.

Rod

[soltakss]

A rough guide for man-sized humanoids is 1 SIZ = 1 Stone or approx 6.3 Kg.

I think it used to be 1 SIZ = 6 ENC, so 1 ENC = 1 Kg.

Work out how heavy the object is in Kg, divide by 6 and that's the SIZ equivalent.

YMMV.

[silent_bob]

Threedeesix,

I am so happy that you are not using the commie metric system:)

Its easiest if you ignore height while determining an existing character or creature and just base SIZ on weight.

Weight it a constant with SIZ, height varies by type of creature. For example, a 15 foot long snake and a 15 foot tall giant should NOT have the same SIZ, one is obviously harder to knockback, harder to lift, harder to hit, etc. But a 600 pound snake and a 600 pound giant should have the same SIZ.

With SIZ, weight is constant. It just makes more sense that way.

I see this come up a lot on these forums and decided for Classic Fantasy 2nd edition I would try to clear it up somewhat. What I did is create a table that showed how much each SIZ equals in pounds. And then derived a separate table that determines height by SIZ according to race. That way you can have a SIZ 10 dwarf and a SIZ 10 human both weigh the same, but the dwarf be only 4'8" tall while the human is 5'6".

For anything other than a player character, SIZ equals weight and height simply doesn't matter.

Obviously every experienced BRP player has their own way of handling SIZ, but that's how I chose to look at it.

Rod

[threedeesix]

Threedeesix,

I am so happy that you are not using the commie metric system:)

I like the metric system for Sci Fi gaming, it feels more futuristic. However, I really think it has the opposite feel in a fantasy game. Just my opinion of course.

Rod

Edit: And Happy 100th Post Silent Bob.

Edited September 14, 2013 by threedeesix

[Atgxtg]

This may, or may not help....

SIZ in general uses a logarithmic doubling progression where each doubling of mass adds 8 to SIZ. SIZ 8 is about 50kg, SIZ 16 is about 100kg, SIZ 24 is about 200kg and so on. This holds true from around SIZ 8 to around SIZ 88. If you want a formula to convert a mass to a SIZ score for a spreadsheet or calculator try log (kg)* 26.575-37.15 (round down).

[Canis latrans popus]

This may, or may not help....

SIZ in general uses a logarithmic doubling progression where each doubling of mass adds 8 to SIZ. SIZ 8 is about 50kg, SIZ 16 is about 100kg, SIZ 24 is about 200kg and so on. This holds true from around SIZ 8 to around SIZ 88. If you want a formula to convert a mass to a SIZ score for a spreadsheet or calculator try log (kg)* 26.575-37.15 (round down).

Oh hey, that might come in handy.

And why do I have deju-vu about this?

And about that part?

[MatteoN]

I like the metric system for Sci Fi gaming, it feels more futuristic. However, I really think it has the opposite feel in a fantasy game. Just my opinion of course.

I thought much of the BRP fanbase was in continental European countries... Having values expressed according to both systems would be appreciated, perhaps.

[Atgxtg]

Oh hey, that might come in handy.

It has come in very handy for me, and perhaps for a few others..

And why do I have deju-vu about this?

And about that part?

Because I've brought this up before. In fact I posted a "revised and expanded SIZ table"on the forms a few years back that fills in weight and mass values for the "missing SIZ" stats on the BRP SIZ table, and attempts to correct the errors on the BRP SIZ table. I think Rosen even used the table for his SIZ stats in BRP Mecha.

I'm the guy who has been working on a vehicle design system for BRP (off and on) and a BRP Bestiary (with Erasmus1966), and both use the x2mass =+8 SIZ progression along with stuff like the cube-square law to extrapolate good BRP game data from real world numbers and existing BRP stats.

The cube-square law really helps when making up giant or midgit creatures. Basically if you double all of a creatures dimensions (length/width/height) you would add 16 to STR and 24 to SIZ. The 2 STR per 3 SIZ ratio holds true here and is why insects are so strong relative to their mass, and why giants can only get so big before thier body can't support or move the mass.

I got a bit more real world formulas converted into BRP terms, too. Such as the relationship between SPEED, Thrsut (read STR in BRP) and Power (i.e. POW). It did take a little more effort to work that stuff out in BRP terms but the payoff is that I have a consistent scale for turning real world data, such as mass, thrust, velocity, and power into SIZ, STR, MOV, and POW.

Eventually I'm hoping to boil it down to the point where a GM can just plug the real world data into a spreadsheet and it will spit out BRP game stats.

[threedeesix]

I thought much of the BRP fanbase was in continental European countries... Having values expressed according to both systems would be appreciated, perhaps.

Nope, there are tons of us over here in The New World.

I did try using both in the earlier versions of the 2nd edition manuscript but it just made it awkward to read. Between all the tables with weapon ranges, spell ranges, height and weights, etc.

If anything, I will add a conversion table to the appendix in the back as well as give simple "off the cuff" conversion notes, things that get used a lot. For example, most maps will be 5 foot and 10 foot square-grid scale. The simple conversion would be 5 feet equal 1.5 meters and 10 feet equals 3 meters.

Rod

[Atgxtg]

For example, most maps will be 5 foot and 10 foot square-grid scale. The simple conversion would be 5 feet equal 1.5 meters and 10 feet equals 3 meters.

Rod

You could always use a 1 pace grid.That way it could be read as either 1 yard or 1 meter.

[threedeesix]

You could always use a 1 pace grid.That way it could be read as either 1 yard or 1 meter.

I thought about that as well at one point, but there are just so many awesome D&D maps to scale with miniatures at the 5 foot scale that I want to be able to use them as is. Plus it's easier when converting existing D&D adventures over to Classic Fantasy.

I do agree however that it would have been a nice easy idea and would (will?) more than likely use it down the road if (when?) I do something different.

Rod

[Atgxtg]

I thought about that as well at one point, but there are just so many awesome D&D maps to scale with miniatures at the 5 foot scale that I want to be able to use them as is. Plus it's easier when converting existing D&D adventures over to Classic Fantasy.

Sounds sensible. Since CF is emulating D&D to some extent,it makes sense to use the same scale and measurements as D&D.

I do agree however that it would have been a nice easy idea and would (will?) more than likely use it down the road if (when?) I do something different.

Rod

it works pretty good for a Japanese setting, too. Their building were based around floor mats that were approximately 3'x6', so all the buildings actually were all built on a 1 pace grid.

[Canis latrans popus]

It has come in very handy for me, and perhaps for a few others..

Because I've brought this up before. In fact I posted a "revised and expanded SIZ table"on the forms a few years back that fills in weight and mass values for the "missing SIZ" stats on the BRP SIZ table, and attempts to correct the errors on the BRP SIZ table. I think Rosen even used the table for his SIZ stats in BRP Mecha.

I'm the guy who has been working on a vehicle design system for BRP (off and on) and a BRP Bestiary (with Erasmus1966), and both use the x2mass =+8 SIZ progression along with stuff like the cube-square law to extrapolate good BRP game data from real world numbers and existing BRP stats.

The cube-square law really helps when making up giant or midgit creatures. Basically if you double all of a creatures dimensions (length/width/height) you would add 16 to STR and 24 to SIZ. The 2 STR per 3 SIZ ratio holds true here and is why insects are so strong relative to their mass, and why giants can only get so big before thier body can't support or move the mass.

I got a bit more real world formulas converted into BRP terms, too. Such as the relationship between SPEED, Thrsut (read STR in BRP) and Power (i.e. POW). It did take a little more effort to work that stuff out in BRP terms but the payoff is that I have a consistent scale for turning real world data, such as mass, thrust, velocity, and power into SIZ, STR, MOV, and POW.

Eventually I'm hoping to boil it down to the point where a GM can just plug the real world data into a spreadsheet and it will spit out BRP game stats.

I would dearly love that to happen. It would make cross-system conversions so much easier. I could have spelljammer vessels that actually make sense, in one sense I mean flying sailing ships in space doesn't make sense.

[Atgxtg]

I would dearly love that to happen. It would make cross-system conversions so much easier. I could have spelljammer vessels that actually make sense, in one sense I mean flying sailing ships in space doesn't make sense.

I got it to the point where it does most of the work. There are a few tricky bits, but I've got working formulas for most things. Right now I am working on simplifying a few things, adjusting scales, and trying to find a better formula for armor and weapons, plus a few spot rules to account for the differences in tech (for example, sailing ships probably need longer turns in chases, and modern aircraft can often chase targets beyond visual range).

But, if it helps, I got the vehicle top speed formula simplfied down to:

SPD= (STR-DRAG)/2 or SPD = (POW-DRAG)/3

You read SPD on the SIZ table using m/s instead of kg.

STR is kg thrust

POW is in decajoules (I think).

DRAG is the vehicles SIZ plus modifers for vehicle type, streamlining, and medium (air or water)

[Canis latrans popus]

I got it to the point where it does most of the work. There are a few tricky bits, but I've got working formulas for most things. Right now I am working on simplifying a few things, adjusting scales, and trying to find a better formula for armor and weapons, plus a few spot rules to account for the differences in tech (for example, sailing ships probably need longer turns in chases, and modern aircraft can often chase targets beyond visual range).

But, if it helps, I got the vehicle top speed formula simplfied down to:

SPD= (STR-DRAG)/2 or SPD = (POW-DRAG)/3

You read SPD on the SIZ table using m/s instead of kg.

STR is kg thrust

POW is in decajoules (I think).

DRAG is the vehicles SIZ plus modifers for vehicle type, streamlining, and medium (air or water)

Does this mean that if I wanted to convert, let's say a mecha from Patlabor, you would take its lifting capacity converted to kgs and use your formula for SIZ to get its STR, rather than, what I did, which is to convert its lifting capacity to Newtons and then apply your formula to derive its STR?

[Mugen]

Does this mean that if I wanted to convert, let's say a mecha from Patlabor, you would take its lifting capacity converted to kgs and use your formula for SIZ to get its STR, rather than, what I did, which is to convert its lifting capacity to Newtons and then apply your formula to derive its STR?

Honestly, both methods should give the same results.

Using kg instead of Newtons allows you for less calculations in "normal gravity" worlds.

[seneschal]

I've carefully saved Atgxtg's charts and comments about SIZ. That stat is one of the hardest BRP concepts to get one's head around, regardless of what other RPG system you came from.

[Atgxtg]

Does this mean that if I wanted to convert, let's say a mecha from Patlabor, you would take its lifting capacity converted to kgs and use your formula for SIZ to get its STR, rather than, what I did, which is to convert its lifting capacity to Newtons and then apply your formula to derive its STR?

Yes. Although technically speaking, Force should be measured in Newtons not kilograms, I used the latter so as to put STR and SIZ on the same scale. That way you know that a vehicle with STR 50 and SIZ 50 has a 1:1 thrust-to-mass ratio, a base acceleration of 1G, and could take off vertically, if the thrust was used as lift.

Since the thrust rating of real world jet engines is often listed in kg or lbs of thrust, I don't feel too guilty about rating STR in kg.

Using kg instead of N will reduce the STR score by about 26 points or so.

Now keep in mind that the STR score is to total thrust of the engine. So if a vehicle is using some of that thrust for other purposes (such as for lifting thhings) that STR wouldn't apply towards the vehicle's speed.

Since we are dealing with real world terms, instead of gobbledygook, 1kg of thrust is approximate equal to 9.81N (that's 1kg mass, multipled by the acceleration of gravity), but a common approximation used in the real world for design purposes is 1kg thrust = 10N. The 10:1 ratio is simple to do in your head, and the 2% error won't really matter for our purposes. In fact, since BRP stat values encompass a range, most of the time the STR score you get with 10:1 will be the same as with 9.81:1, and even when they differ the difference will only be by a point. The 10:1 ratio is also why I rated POW in terms on kilojoules instead of joules - it lets me rate STR, SIZ and POW on the same relative scale (sort of).

One of the little speed bumps I trying to work around is that since a value of 1kg would be about a -37 SIZ if the doubling progression were used beyond the SIZ 8-88 range, a modifier has to be added to some of the equations to get the correct values. For example, if a Vehicle had a thrust of 100kg (STR 16) and a velocity of 100m/s (SPD 16 on the SIZ table) it should have a power rating of 100000J (100x10x100) or 10000dJ (POW 95). I would like to work it out so I can just add STR to SPD to get POW but can't because a value of 1 doesn't equal a stat on 0 on the SIZ table.

Another speed bump is that when engineers design veicles in the real world they use different reference areas to calculate the drag area of the vehicle. This means that cars, boats, airplanes, and submarines all use different reference areas and drag coefficients to determine their respective drag areas. This means that a car and a airplane with the same drag coefficients are not necessarily streamlined to the same extent, since they are not using the same reference areas. The car is using frontal area, while the plane is using it wing area.

Sorry if I got too technical here. Most of this "nuts& bolts" stuff I am planning on hiding away. People won't have to know or use it to stat us or design vehicles. I, unfortunately, do have to know and use it to make sure it all working out correctly behind the scenes. But, since I do have the "real" info on hand, it can make it easier for someone to write up something specific if he has real world terms to work with and wants game stats.

[Atgxtg]

Honestly, both methods should give the same results.

Using kg instead of Newtons allows you for less calculations in "normal gravity" worlds.

Not quite. Since 1kg thrust is approximately 9.81N (say 10), then he N will be be about 10 times the kg,or about 26 points higher on the SIZ table.

[Atgxtg]

I've carefully saved Atgxtg's charts and comments about SIZ. That stat is one of the hardest BRP concepts to get one's head around, regardless of what other RPG system you came from.

LOL! Me too.

I've actually been working of some stuff to let people do more with SIZ, and make it easier to wrap their heads around.

Basically the problem is that the SIZ table progression is a logarithmic doubling progression rather than a linear progression. So I got a table that you can use to multiply values using the SIZ table. For instance, x2 = +8 SIZ, x3 is about +12 SIZ, x4 is +16 SIZ, x5 is about +18 SIZ.

I also got a sheet for working up stats for giant sized creatures that does the whole cube-square law thing for you so you don't have to. If, for instance, you want to make an animal or object twice as big (length, height and width), you look up x2 on the sheet and see that you should add 24 points of SIZ and 16 points to STR and CON (for realistic giants -fantastic ones should scale STR at the same rate as SIZ).

[Canis latrans popus]

Yes. Although technically speaking, Force should be measured in Newtons not kilograms, I used the latter so as to put STR and SIZ on the same scale. That way you know that a vehicle with STR 50 and SIZ 50 has a 1:1 thrust-to-mass ratio, a base acceleration of 1G, and could take off vertically, if the thrust was used as lift.

Since the thrust rating of real world jet engines is often listed in kg or lbs of thrust, I don't feel too guilty about rating STR in kg.

Using kg instead of N will reduce the STR score by about 26 points or so.

Now keep in mind that the STR score is to total thrust of the engine. So if a vehicle is using some of that thrust for other purposes (such as for lifting thhings) that STR wouldn't apply towards the vehicle's speed.

Since we are dealing with real world terms, instead of gobbledygook, 1kg of thrust is approximate equal to 9.81N (that's 1kg mass, multipled by the acceleration of gravity), but a common approximation used in the real world for design purposes is 1kg thrust = 10N. The 10:1 ratio is simple to do in your head, and the 2% error won't really matter for our purposes. In fact, since BRP stat values encompass a range, most of the time the STR score you get with 10:1 will be the same as with 9.81:1, and even when they differ the difference will only be by a point. The 10:1 ratio is also why I rated POW in terms on kilojoules instead of joules - it lets me rate STR, SIZ and POW on the same relative scale (sort of).

One of the little speed bumps I trying to work around is that since a value of 1kg would be about a -37 SIZ if the doubling progression were used beyond the SIZ 8-88 range, a modifier has to be added to some of the equations to get the correct values. For example, if a Vehicle had a thrust of 100kg (STR 16) and a velocity of 100m/s (SPD 16 on the SIZ table) it should have a power rating of 100000J (100x10x100) or 10000dJ (POW 95). I would like to work it out so I can just add STR to SPD to get POW but can't because a value of 1 doesn't equal a stat on 0 on the SIZ table.

Another speed bump is that when engineers design veicles in the real world they use different reference areas to calculate the drag area of the vehicle. This means that cars, boats, airplanes, and submarines all use different reference areas and drag coefficients to determine their respective drag areas. This means that a car and a airplane with the same drag coefficients are not necessarily streamlined to the same extent, since they are not using the same reference areas. The car is using frontal area, while the plane is using it wing area.

Sorry if I got too technical here. Most of this "nuts& bolts" stuff I am planning on hiding away. People won't have to know or use it to stat us or design vehicles. I, unfortunately, do have to know and use it to make sure it all working out correctly behind the scenes. But, since I do have the "real" info on hand, it can make it easier for someone to write up something specific if he has real world terms to work with and wants game stats.

Technical is good even if my background isn't in physics or mechanical engineering. Having an idea about your reasoning is exceedingly useful in evaluating how to approach using your methods in statting up mecha for my game.