Simplifying Gurps Space world creation

[Lanfranc]

Originally Posted by Brett

Finally, one of the rights of an author under copyright law is not to have his work distributed in a garbled form. This is why I do not distribute my Excel instantiation of the GURPS Space starsystem generator. I couldn't get the spacing on moons to come out right, I corrected some acknowledged but officially uncorrected errata, and I added a few calculations (such as the level of visible illumination) that are not in the original. So I would legally need explicit permission to distribute mine. The above permission only seems to me to apply to a faithful and complete instantiation.

That seems like an overly strict interpretation. After all, you're not distributing Zeigler's and Cambias's GURPS Space itself, which is protected by author's rights; you're distributing your own original and unofficial work which is simply based on the rules in GURPS Space.

As long as it is supplied with the required disclaimers and a bit of documentation, I can't honestly see where the problem would possibly be.

[Langy]

Especially if you document exactly where your program goes different.

Then again, I can't figure out why you'd have to use macros in order to do the moons - it looks relatively straightforward from my position.

[Agemegos]

Originally Posted by Langy

Especially if you document exactly where your program goes different.

I did, naturally.

GURPS Handbook of the Planets

A computerised game aid to automate the world design sequence from 'GURPS Space' (4th edition)

Release 1.0 5-Nov-07

'GURPS Space' is a trademark of Steve Jackson Games, and its rules and art are copyrighted by Steve Jackson Games. All rights are reserved by Steve Jackson Games. This game aid is the original creation of Brett Evill and is released for free distribution, and not for resale, under the permissions granted in the <a href="http://www.sjgames.com/general/online_policy.html">Steve Jackson Games Online Policy</a>.


Specification

This 'GURPS Handbook of the Planets' is a game aid for gamemasters and other worldbuilders using the world design sequence from 'GURPS Space' (Fourth Edition). I wrote it as an Excel workbook entirely without macros, for three reasons. First, because that makes it widely available to people using different personal computers and operating systems. Second, so that users could feel reasonably safe from the damage that careless programmers can cause with macros and powerful programming languages. Third, because it was an interesting challenge.

My objective in writing this game aid was to implement the rules as written as far as possible, subject to the constraint that it should be an Excel workbook with no macros. I have resisted the occasional temptation to add to or 'improve' the rules, except in three types of circumstances. First, where the rules as written cannot be implemented without macros, either because they require loops or because they leave things to the discretion of the user (discretion cannot be programmed into a spreadsheet). Second, where I am convinced that the rules as written embody clear errors in physics and astronomy (which is to say, in some particulars involving tides). Third, in cases where the spreadsheet could calculate useful values (such as the temperature of a planet at perihelion and aphelion, or the level of visual illumination, or the apparent size of the sun or a moon) from details that were already available (ie. without making up new 'facts' about the system).

The purpose of this game aid is to relieve the GM of those parts of the star system generation sequence that are routine and tedious and which require intricate calculations. It is naturally unsuitable to executing the parts that require intelligent interpretation, creative input, and an understanding of the requirements of the user's setting, campaign, and story intentions. Therefore I have omitted steps 11 to 14 of the basic world building sequence and steps 33 to 39 of the advanced world building sequence, which depend very much on the GM's setting and story ideas, and which are comparatively simple and interesting. This game aid generates the astronomical and planetological detail as far as calculating the carrying capacity of each world. It also calculates wealth and economic volume for given population and tech level. The rest of the social and political details are left to the user.

The Handbook instantiates both "GURPS Space chapter four—Basic Worldbuilding" and "chapter five—Advanced Worldbuilding". That is to say, you can use it in entirely random mode, or you can specify the some or all of the characteristics of the star[s] in the system and have it randomly generate the planets, or you can design a planet and have it generate the rest of the system randomly, or you can design the star[s] and one 'main' planet and have the Handbook randomly generate the rest of the system.

I have made every effort to implement the rules as written, except for known or strongly suspected errata. But have not been able to do this in every respect, because of the choice to design the Handbook as a spreadsheet. "If the moons turn out to be too close to each other, start over" cannot be implemented without macros.

This generator calculates everything about a planet up to its carrying capacity (if the user specifies a technology level) and economic volume and typical wealth (if the user specifies a setting TL and a population of the planet). It does not generate settlement type, population, world unity, society type, control rating, or any installations or trade routes, though there is space on the sheet for a user to add these himself or herself. I decided that these things were too dependent on campaign and story requirements to be worth my trouble in coding random generation. Users may generate the results at random by hand and type the results into the spaces on the sheet if they wish. That is neither difficult nor particularly time-consuming.

The Handbook is designed in such a way that your user number (which you may choose, alter etc.) and a system number are combined to make a seed for the pseudorandom number generator. If you put the same user number and system number in again [and the same control settings, if you are using the design features], the Handbook will generate exactly the same starsystem. That way you can choose a user number to make your universe not exactly the same as every other and treat the system number as a catalogue number: the system is completely defined (within that universe) by the system number. A GM can compress a complete system description into his or her notes as a single number. Players can 'look up' starsystems in the Handbook, given their numbers.

I have been reluctant to improve upon the rules as written, except in cases where I am sure they contain scientific errors. The exceptions have been that I have added a few minor features to calculate properties of the planets and moons that either require involved calculation or require access to intermediate data that I have not presented on the display pages. Such are:

• The Handbook calculates and displays the average temperature of a planet or moon at perihelion and aphelion, not just the annual average average.
• The Handbook calculates and displays the apparent size of the sun as seen from any planet or moon, in the case of planets, the apparent size of its moons if any, and in the case of a moon, the apparent size of the planet it orbits.
• The Handbook displays the visual illumination on a world (as a proportion of that on Earth): that is, how much visible light there is.

Then again, I can't figure out why you'd have to use macros in order to do the moons - it looks relatively straightforward from my position.

You need macros to do open-ended "while" loops. Without them you can only do definite-length "for" loops. The official rule is (p. 116) "If any two of the major moons orbit within one planetary diameter of each other, re-roll ... both". That's a potentially indefinite process, and I couldn't figure out how to do it in a spreadsheet.

[Langy]

Instead of using a loop, why not rewrite the code so it's impossible for two major moons to be within one planetary diameter of each other (five for terrestrial planets)?

Example, for gas giants your first major moon would work as normal. Your second one, however, would only roll 2d6+1d5+3 +IF(that random value >= first major moon's value,1,0)*. This would make it so you can't place two moons in the same orbit and it has the same mathematical properties as if everything was just rerolled.

*After some re-thinking, I'm not sure this would work out right. Instead, instead of rolling 'dice' just get a random value between 1 and 216 for the first one and map that to a value - this would be mathematically identical to rolling 3d6. Then subtract the number of possibilities in 3d6 for that value (for example: a value of 4 has only 3 possiblilities in 3d6 - 1,1,2, 1,2,1, or 2,1,1) and get a random number between 1 and 216-(possibilities) and map those values to the remaining possible numbers. This *is* mathematically identical to just rerolling every time you get one of the impossible orbits.

This might be slightly more work than using macros, but it's also a lot more compatible.

It's not exactly the same as the system in Space, but it's mathematically identical unless I'm completely missing something, which makes it quite good enough for a program.

[Agemegos]

Originally Posted by Langy

It's not exactly the same as the system in Space, but it's mathematically identical unless I'm completely missing something, which makes it quite good enough for a program.

Very good! I hadn't thought of that!

[Artifact]

Brett -

Have you shared your system generator? It sounds great and I have seen all of your posts (and work) pushing for corrections to the calculations - I did not see it with the other game aids. I think I saw that you were concerned with posting it at one point.

Thanks

[Agemegos]

Originally Posted by Artifact

Have you shared your system generator?

As a beta test I gave copies to some forum posters who have agreed not to distribute further copies.

[Artifact]

I have undertaken converting a bunch of old RPG material (created for Space Opera originally - I still have the books from about 1981) and some fictional material into a GURPS setting. I have been starting to work on planets and systems, but as has been pointed out, that is a long process if there are multiple systems. It is organized as a webpage at the moment, which is public, but still needs lots of work.

If you are willing to share your work with with one more person I would be grateful!

[Obi]

Originally Posted by Agemegos

As a beta test I gave copies to some forum posters who have agreed not to distribute further copies.

Is it possible that this many years later you could still provide access to this planet generator? If it doesn't work on current OS that's perfectly fine. Just was on a rabbit hole crafting my fictional world and would love to try your tool if it's still available.


Edit: Found it!

[Agemegos]

Originally Posted by Obi

Is it possible that this many years later you could still provide access to this planet generator? If it doesn't work on current OS that's perfectly fine. Just was on a rabbit hole crafting my fictional world and would love to try your tool if it's still available.

Well, I still have the beta.23 version of the workbook, and it still runs fine as far as I can see, and as far as it goes (which is: as fair as Habitability, Affinity, and carrying capacity). But I regret ever having released it, because I think it had the effect of inhibiting competent programmers from coding a proper generator with a proper user interface using an actual programming language. Such a proper generator would be possible to modify and maintain, where my Excel workbook is a code maintenance nightmare.

Did anyone complete a proper instance of the GURPS Space (4th edition) star system and planet generation sequence?