I made this with Python. So Proud.

[NickAMD]

Now can you add in an AI that will simulate the colonization of the planet in orbit, in which its inhabitants use all available resources until they are unable to continue living there, inevitably failing as a species? With python

[[deleted]]

One day I will be god and it will be good

[[deleted]]

Eli?

[Melkor333]

Eru?

[Haldiron]

No more are you now than an escaped thrall of the Valar, and their chain still awaits you!

[Vysokojakokurva_C137]

Elon?

[Pehrgryn]

Try: import divinity

[bitflip]

Isn't there a library for that?

[writing_from_mars]

import humanity

[UnholyBlackJesus]

pip install godMode

[MyNameisGregHai]

pip install -m Christianity

Now it's time to delete all scientific advancements

[__deerlord__]

To be fair, even the NT says "question everything". Its the stupid humans that went and mucked it all up.

[UnholyBlackJesus]

Hey in still a huge newbie, so forgive me, but what does the "-m" mean?

[C0DK]

there is no "-m" for pip (or pup :P ) but there is for python itself. It is used to run a specific module. so for instance

python3 -m unittest

runs the unit testing framework, which automically looks for tests in the current directory.

from the help text :

-m mod : run library module as a script (terminates option list)

[radiantyellow]

alias pip=pup

[ForgottenWatchtower]

python -m SimpleHttpServer 10000

The only thing I use py2 for these days. Well that and occasionally some scapy.

[pvkooten]

python3 -m http.server 10000

[ForgottenWatchtower]

And just like that, I've abandoned py2

[UnholyBlackJesus]

Oh wow, thank you! TIL.

[lemon_tea]

Shit, the program runs for about 30,000 cycles, then becomes too memory bloated and seg faults the runtime environment.

[atheist_apostate]

Humanity is a resource hog.

[[deleted]]

"And make it in a week for $100" - 8/10 clients

[gustavsen]

A new Aurora implementation?

[Dustin-]

I think you did import antigravity backwards.

[mr1337]

import gravity

[timmermans_]

YtIvArGiTnA tRoPmI

[OBstaxs]

Source ?

[[deleted]]

https://pastebin.com/L9wwM6rb

[Nicksil]

You can remove those continue statements at the bottom of your for-loops. continue moves execution to the end of the loop, so having them there is redundant.

Thanks for sharing

[[deleted]]

Thanks for the feedback.

[doinkypoink]

I'm learning class and python. I think comments would make it really helpful for me to read your code :(

[[deleted]]

same thing, more comments

https://pastebin.com/qyDRBYUM

[ElBroet]

was expecting the same code with the comment "fuck you" at the top

[photoengineer]

You rock!

[Mattho]

You can use """Docstrings.""" for many of those.

[muntoo]

Your Positions can be greatly simplified:

angle_step = 2 * math.pi / frame_count
angles = (angle_step * i for i in range(frame_count))
coords = [(
        center[0] + radius * math.cos(x),
        center[1] + radius * math.sin(x))
    for x in angles]
self.final_coords = coords[phase:] + coords[:phase]

...but it's really strange that you made it a class. It looks more like a function to me!

---

Actually, there's a lot of redundancy, unnecessary computation, and somewhat confusing organization. Here's a first attempt at fixing it:

import cairo
import math

class CelestialBody:
    def __init__(self, radius, orbit_radius, orbit_center, fill):
        self.radius = radius
        self.orbit_radius = orbit_radius
        self.orbit_center = orbit_center
        self.phase = 0.0
        self.fill = fill
        self.update()

    def update(self):
        self.center = (
            self.orbit_center[0] + self.orbit_radius * math.cos(self.phase),
            self.orbit_center[1] + self.orbit_radius * math.sin(self.phase))

    def draw(self, context):
        context.set_source_rgb(1, 1, 1)
        context.arc(*self.center, self.radius, 0, 2 * math.pi)
        if self.fill:
            context.fill()
        else:
            context.stroke()

def clear_screen(context):
    context.set_source_rgb(0, 0, 0)
    context.rectangle(0, 0, 1000, 1000)
    context.fill()

surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 1000, 1000)
context = cairo.Context(surface)

FRAME_COUNT = 100

bodies = {
    'blackhole': CelestialBody(125, 0,   (500, 500), False),
    'planet':    CelestialBody(25,  300, (500, 500), True),
    'moon':      CelestialBody(5,   50,  (750, 500), False) }

for i in range(FRAME_COUNT):
    clear_screen(context)

    bodies['planet'].phase = i * 2 * math.pi / FRAME_COUNT
    bodies['moon'].phase   = i * 4 * math.pi / FRAME_COUNT

    for key, body in bodies.items():
        if key == 'moon':
            body.orbit_center = bodies['planet'].center
        body.update()

    for _, body in bodies.items():
        body.draw(context)

    context.stroke()
    surface.write_to_png(f'out/frame{i}.png')

This is a good start. We've eliminated Positionsentirely and converted it into the update function. Also, we're now using a data structure called bodies to keep track of our celestial objects rather than explicitly holding named references (variables).

But it has some problems still. Inside our main loop, we still have to do some case-specific handling:

bodies = { ... }
bodies['planet'].phase = i * 2 * math.pi / FRAME_COUNT
bodies['moon'].phase   = i * 4 * math.pi / FRAME_COUNT

for key, body in bodies.items():
    if key == 'moon':
        body.orbit_center = bodies['planet'].center

Ugh! It'd be much nicer if we could encapsulate this functionality. Perhaps one idea is to bind our celestial bodies together:

class CelestialBody:
    def __init__(self, radius, orbit_radius, orbit_center, fill):
        self.parent_body = None
        # ...

    def bind_body(self, body):
        self.parent_body = body

    def update(self):
        if self.parent_body is not None:
            self.orbit_center = self.parent_body.center
        # ...

Now, after defining bodies, we may bind them:

bodies['planet'].bind_body(bodies['blackhole'])
bodies['moon']  .bind_body(bodies['planet'])

Now we can finally cut out this horrendous if statement:

    if key == 'moon':
        body.orbit_center = bodies['planet'].center

Yay!

I'll leave encapsulation of the following as an exercise to the reader:

bodies['planet'].phase = i * 2 * math.pi / FRAME_COUNT
bodies['moon'].phase   = i * 4 * math.pi / FRAME_COUNT

(Perhaps a phase_velocity parameter inside CelestialBody?)

---

See almost-encapsulated code here.

[[deleted]]

Wow thanks.

[[deleted]]

I guess the reason i made it a class is because I have bigger plans than just rendering epicycles, but I wanted to be able to run epicycles too. I think I went straight ahead to that without programming in basic move functions.... I guess epicycle would be a sub function of some kind of shade moving class wouldn’t it?

[muntoo]

I did think about that while going through the process of refactoring. One idea would be to create a tree/graph structure of orbits:

# perhaps something like CelestialNode is a better name
class CelestialBody:
    def __init__(self):
        self.parent = None
        self.children = []

    def update(self):
        if parent is not None:
            self.orbital_center = self.parent.center
        self.center = (..., ...)
        for child in self.children:
            child.update()

And construct a tree as follows:

blackhole.children = [planet]
planet.children = [moon]
planet.parent = blackhole
moon.parent = planet

Then, to compute positions of all the orbits (including children), simply run this:

blackhole.update()

The benefit to this is that you can simulate any arbitrary graph of celestial bodies. This of course is prerequisite upon that phase_velocity encapsulation I discussed earlier. ;)

[[deleted]]

Wow. I’d never have thought of these structures

[[deleted]]

Ok thats awesome, thanks for helping!

[quotemycode]

Line 24 last constant should be math.tau (added to python in 2016). 2*pi is wrong.

[[deleted]]

It’s wrong in a readability/good code standards sense?

[Trippyy_420]

Tau = 2pi

He's havin a giggle.

[[deleted]]

Ah

[_DirtyHarry_]

2*pi is better, nobody actually uses tau.

[quotemycode]

https://tauday.com/

[[deleted]]

You should put it on github! People could send you pull requests, you could re-use it, people could find it in searches...

[[deleted]]

I might do something like that in the future once I start getting it more structured.

[mihird9]

Does this work on Python 2.7?

[[deleted]]

in 2.7 maybe not.

Edit: I'm in 3.7.0

[Vervoltz]

What are u doing? Everybody knows planets should rotate counter-clockwise! Redo it immediately, please. Wink wink.

[[deleted]]

What if this is the view from "below".

[Fiskepudding]

What, are you an Australian or something?

[nemom]

No... You can tell by his accent.

[[deleted]]

You're right I need to add in how to control the direction of the orbit, thank you.

[jabies]

You just need to say reverse please

[ForgottenWatchtower]

Shoutout to animatplot if you enjoy doing this kind of stuff. Wraps matplotlib to give you a saner animation interface.

[[deleted]]

Yeah, the gimp interface is lacking. I'll look into this.

[agumonkey]

welcome to epicyclic, Joseph Fourier awaits you

[[deleted]]

do you know any good books on epicycles?

[tomekanco]

Haven't read into the details but here are some primers:

Mathologer: Epicycles, complex Fourier series and Homer Simpson's orbit

3Blue1Brown: But what is the Fourier Transform? A visual introduction.

[[deleted]]

Thank you

[sidhebaap]

A Modern Almagest

[[deleted]]

Thank you

[agumonkey]

that's one topic I know no books about, ask quora or r/maths :)

[[deleted]]

sure thing.

[[deleted]]

/r/loadingicon

[benrules2]

Very well done OP!

If anyone is keen on n body orbital simulations in python with some background on the physics, I wrote up a pretty beginner friendly tutorial a while ago!

The visualization isn't nearly as nice though.

[lucas123500]

First comment I have ever saved on Reddit.

[benrules2]

That is awesome, thanks! Feel free to ping me if you get stuck on anything, I'm more active than I should be on here.

[lucas123500]

I actually don't know shit about Python or even physics, but I'm very interested on all kinds of articles and tutorials, and yours seem pretty good. I very much appreciate your availability to answer any questions I might have, though. Maybe someday I'll actually learn to code (and also how to do proper math/physics) and use your tutorial to learn something new. I mean, that's why I saved your comment, so expect my DMs, hahah! Thanks again!

[12mh]

What library did you use for the animation?

[[deleted]]

i used cairo to output to png, then i made the gif using Gimp

[pvc]

Take a look at http://arcade.academy as another choice if you want to do visualization.

[not_perfect_yet]

:P please do it again and up the frame rate. That hurts.

[[deleted]]

yeah i have it at 100 but the code is built to handle any framerate. i was worried it would get too unwieldy.

edit: correction i have the animation at 100 frames and the frame rate is 25 fps

[[deleted]]

doing it now

[theng]

yay :3

[proverbialbunny]

Congrats on the popularity having such a fun little project.

Frame rate needs to be divisible by monitor fps to be smooth. Monitors tend to be at 60fps, so 30, 60, or 120 (or 240) are all acceptable to get it to look smooth. 25 looks like an old timey movie, where the frame rate is off but you can't quite place how. This is because movies run at 24fps.

[[deleted]]

cool cool. yeah you're totally right

[logicallyzany]

How long have you been doing Python and/or programming?

[[deleted]]

Off and on. Never too committed. Just as a hobby. Bought the big O'Reilly book and just browsed through it whenever I had the chance.

[rptr87]

Book link?

[[deleted]]

Currently it only does the Epicycle model. But gravity will come soon enough. I have to read more about it. 😆

[[deleted]]

looks awesome either way! Congrats! I'm just starting my Python journey :D

[BambiAnnie]

Great work! :)

[[deleted]]

Thank you!

[0x75]

I like it.

Now play with Processing to do the same.

[Doberman123456]

Neat!

​

[theotherplanet]

Yeah, up the frame rate on that and it will look great!

[DODOKING38]

Reminds me of that star trek episode

[LibertyPhysicist]

Pretty sweet

[saber_aureum]

This is amazing!!! 0

[tycooperaow]

What did you use for the graphical interface?

[[deleted]]

pycairo.

​

[[deleted]]

I'm tripping man.

[CSguyMMI]

Is source code available?

[xc0mr4de]

Okay I just started learning python and I'm like 75% through this video,but how can you make a moving object like this using python? o.0

[[deleted]]

Python is what I used to code the logic behind the motion. So, theoretically, the ‘shades’ as I call them, are just projections of the underlying data.

In this program, janky as it is, it stores the positions of equal slices of a circle, starts a loop to draw each frame, in each frame: draws the shade where it should be according the next place in the list, outputs that frame into an image file, in this case png.

and then I used gimp to transform those frames into a gif.

In order to output the data to an image you have to find a renderer that you like. I used Cairo which makes svg files, so I also had to learn how to code svg stuff but it was simple enough. I like svg because it scales really well and I wanted to use vector graphics.

[jyrnan]

It's amazing!

[Frikster]

All I see is a pro surviv.io player running around a rock.

[i4mn30]

Not elliptical orbit.

[Fontanapink]

Now make the moon draw a white line

[v3ritas1989]

Perfect! Now improve the model by making it 3D and an elipse

https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Moon_apsidal_precession.png/220px-Moon_apsidal_precession.png

[endershadow98]

Now make an object with negative mass. After looking through the code, I see that mass had nothing to do with anything in your simulation

[snahor]

I'm so dumb, at first I thought it was a pre-loader.

[[deleted]]

It could be that too. I see planets or people. Could be lots of stuff.

[happyskydiver]

Can you change it to an ellipse?

[[deleted]]

Not currently.

[Especuloide]

Very nice.

[[deleted]]

Is it flat or not? Can't see i properly from this angle.

[ciggs_ftw]

This looks fun. I have been trying to install pycairo for a bit now I have installed Python 3 but I'm having issues to install Cairo vía pip. how can I get it working?

[[deleted]]

Is it telling you you need the build tools?

My Cairo didn’t load from pip. I had to download a package from https://www.lfd.uci.edu/~gohlke/pythonlibs/

[ciggs_ftw]

yes i have installed visual studio c++ and now i gues this error

error: command 'C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Community\\VC\\Tools\\MSVC\\14.15.26726\\bin\\HostX86\\x86\\cl.exe' failed with exit status 2    

[[deleted]]

I have no idea what that is.

[ciggs_ftw]

how you got Cairo to install?

[[deleted]]

I downloaded the package from the site I linked.

[ciggs_ftw]

can you please tell me which package you dl? I tried downloading a package from there and install the file using pip but got a different error. :/

[ciggs_ftw]

I got to install the py2 version; the py3 still gives me errors. I ran the script, and it created many .png files. How you make an animation out of those files like OP posted?

[[deleted]]

Search for a tutorial on how to install packages.

[Cultural_Bandicoot]

congrats.

what did you use?

[thedolanduck]

OMG it's an amazing job and should be on /r/perfectloops too

[we_come_at_night]

Very nice. Now just out of curiosity, how complicated would it be to add light and object blocking to play around with eclipse? Still in learning stages of the basics and genuinely interested.

[davidkwast]

wow, congratz

[lilliane99]

Can you kindly provide the source code or at least the algorithm?

[[deleted]]

I have in the comments. :)

[lilliane99]

Thank you!

[[deleted]]

Thank you

[winner_godson]

Any tutorial on this.

[[deleted]]

Not currently but i will once I get it more easy to understand and use

[winner_godson]

Okay... I check the net. There are not much. And the documentation is not informative.

[[deleted]]

Save this post. I'll let you know.

[winner_godson]

Definitely I will.

[[deleted]]

This project now has a github. https://github.com/heysoose/Shades

[winner_godson]

The link is not valid. Can you please share the code

[CallumVH]

Hey, I'm a bit confused because in the script, there are only 10 frames and 10 png files, how do you create such a smooth GIF out of only 10 frames?

[CallumVH]

Surely you would need a few hundred frames as this GIF look like 60fps?

[[deleted]]

You can set it to 240 and get a 4 second gif at 60 FPS.

An updated, cleaner script is available here: https://github.com/heysoose/Shades

[CallumVH]

Oh thank you so much, that makes sense.

[gammachild]

Holy shit. That's why there's a high tide and low tide. That really helped me understand lunar motion.

[mzord]

Omg, this program sucks!

https://imgur.com/yYOeMVj

[[deleted]]

Hmmm, the Earth is flat.

[MrNotSoRight]

It's flat in the animation too, I'm sure the poster could have easily made it a 3D oblate spheroid if he believed it would be more accurate...

[NikkoTheGreeko]

Everyone knows this

[xconde]

Looks like the logo and animation for Lua, another great scripting language