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# World in 7 days, Day 1: Galaxies

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The thing that drew me to programming was simple: ability to create. I always loved travels, adventures and discovering the undiscovered. I used to watch this old 60s cartoon called Jonny Quest, about boy having adventures, but when I looked out the window, I only saw blocks of flats in my city, and couldn't imagine that this was possible any more, so I spent time playing with my computer. When I was bit older Cartoon Network ran a reimagining of those stories - The Real Adventures of Jonny Quest. And they had adventures IN COMPUTER!

Now, this later on was looked down upon as not being able to stand the test of time, but for me it was always amazing. After I saw the first episode I bought 'C++ in 24 hours' and started writing an OS/AI/VR system (do keep in mind that I was young ;) ). Obviously it didn't do much except for saying 'hello, mantis!', but it set me on a road to where I am now.

Later on I've picked up the subject of creating worlds couple times, with changes in complexity and scope. I have done some basic ROAMing planets and atmospheric scattering, but I've never put it together into a coherent project. When I was finishing my last project though, I've bumped yet another time to blog of a guy who created the most amazing planets that I ever saw - Journal of Ysaneya. Now, these days his screenshots are down, which is a real shame, because they were AMAZING. Just reading the names of the entries gave me idea, why not do what I always wanted to do? Well, the complete world is a complex piece of engineering, and seeing how Ysaneya worked on his projects for couple years and I'll be wanting to finish mine in 7 days, there will have to be some compromises. Nevertheless, I set out on a journey, and am awaiting with curiosity where it will take me.

The scope is following:

1) I want to generate at least one galaxy
2) That galaxy needs to have proper amount of stars (I'm talking billions here)
3) Each star needs to be blue, white, yellow, orange, red or brown dwarf
4) Each star may have planets around it
5) Planets may have atmosphere/water (the M-class planet, to use Star Trek terminology. I'm not a big ST buff, but I like their naming convention)
6) Planets with atmosphere/water may have plants

Soooo.

How would I divide the work:

Day 1) Shaping of galaxy, preparing density maps
Day 2) Dividing galaxy into octree, allowing for tens (or hundreds?) of billions of stars
Day 3) Go to planetary system mode, create orbits for planets, display planet/sun
Day 4) Create proper terrain on the planets
Day 5) Create atmospheric effects
Day 6) Create L-system plants
Day 7) Polish (rest?)

Yeah, I don't get any smarter or less optimistic in my estimates. But I decline to give in

DAY 1:

I've started by playing around with Unity and figuring out a way to most efficiently represent thousands of stars. After short deliberation I chose the new ParticleSystem. I could access all the particles as an array, and tweak their parameters. I've looked up the wikipedia article on star types, and noticed something which surprised me: most of the stars aren't in fact white, but white are just that much more visible. Which meant that Ysaneya's approach to generating galaxies (using octree to look up stars depending on their colour) made sense. Well, that much I didn't doubt.

To generate correct shape I have combined a bell curve with the equation of:float a = 2;float b = 2;float c = 0.7f;float d = 0;float e = 2.71828f; probability = Mathf.Pow (a * e, -((dist * b)*(dist * b)) / (2 * c * c) + d);
and a picture that I have drawn in GIMP

To get the following result:

You can also see 'record' 'stop' and 'play' buttons there. What do they do? Well, your voice is your key: I take the recording sample, get its hash value, and pass it as a Random's seed value. That means that each person will have his own personal universe, unique to himself (or as close to unique as the hash function allows).

Basically, this means you can create universe by saying 'BE!' ;)

That's it for tonight! See you soon!

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Story so far:

Days 2, 3 and 4: Stars and Planetary Systems
Day 1: Galaxies

## 1 Comment

If you're interested in stuff like this then you can checkout how open source games do it to.

Pioneer (http://pioneerspacesim.net/) is open source (https://github.com/pioneerspacesim/pioneer) and features procedural galaxy, star systems, planets you can land on etc.

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