Suggestions! (new)

What did you draw?
SFastro
Posts: 2
Joined: Wed Jan 14, 2015 1:01 am

Re: Suggestions! (new)

Postby SFastro » Wed Jan 14, 2015 1:26 am

Hi! I'm a physics & astronomy teacher - would love to use GSim for student projects! But I'm having trouble with these bugs / missing features:

-Saving / Loading extremely buggy. Sometimes screen is stuck panning after load, saved objects missing/altered after load, time coordinates messed up after load, etc. Could use a more traditional, robust Save / Load system with files instead of code.

-Need a "reset" button that snaps the system back to its initial configuration at t=0. This would be great for systematically building systems by trial and error.

-Need a merge option for asteroids and fixed stars.

-Would like to be able to edit the position and velocity of existing objects with the mouse. Clicking on an already created object and dragging could change its velocity; shift+dragging could change its position.

I've tried a LOT of gravity simulators and GSim is the most promising for student use. Hope to see an updated version soon!

NealCruco
Posts: 197
Joined: Thu Mar 27, 2014 8:26 pm

Re: Suggestions! (new)

Postby NealCruco » Sat Jan 17, 2015 9:41 pm

Welcome to the forums!
Andy has a downloadable version with these features, or at least most. It only costs $5.

A Random Player
Posts: 523
Joined: Mon Jun 03, 2013 4:54 pm

Re: Suggestions! (new)

Postby A Random Player » Sat Jan 17, 2015 11:11 pm

SFastro wrote:Hi! I'm a physics & astronomy teacher - would love to use GSim for student projects! But I'm having trouble with these bugs / missing features:

-Saving / Loading extremely buggy. Sometimes screen is stuck panning after load, saved objects missing/altered after load, time coordinates messed up after load, etc. Could use a more traditional, robust Save / Load system with files instead of code.

-Need a "reset" button that snaps the system back to its initial configuration at t=0. This would be great for systematically building systems by trial and error.

-Need a merge option for asteroids and fixed stars.

-Would like to be able to edit the position and velocity of existing objects with the mouse. Clicking on an already created object and dragging could change its velocity; shift+dragging could change its position.

I've tried a LOT of gravity simulators and GSim is the most promising for student use. Hope to see an updated version soon!

I'll put in my $0.02 while Andy sees this. (Might help fix some of the bugs.)
Saving and loading are indeed quite buggy, but many of the problems I've noticed are because of merging; a "new" body resulting from a merge is saved in place of the old ones, which don't get saved.
Try with merging on:

Code: Select all

Gravity Fun at TestTubeGames.com: [ForceGr: r^(-2)], [x0: 122.5,y0: 25,vx: -7.998894,vy: 1.333149,t0: 0,who: 3,m: 0,c: 0], [x0: -10,y0: 7.5,vx: -0.03,vy: 0,t0: 0,who: 4,m: 1000,c: 1], [x0: 120,y0: 10,vx: 0,vy: 0,t0: 0,who: 4,m: 1000,c: 1]

Then take the code it generates and put it back in. Results in something completely different. (Not sure who I'm really talking to anymore, but oh well.) This could be fixed by not doing anything for merged bodies, remembering only what's added where. Time reversal, on the other hand...

Resetting to t=0 would basically clear everything, since nothing would have been added yet. Unless you're creating everything at t=0, which this would indeed be helpful. Right now you can save and load the code when you "get" a good trajectory.
Spoiler: show
Though I do like the idea of going back to an earlier point to change or add something, which can't be done with the current time-reverse tools in many cases. (Chronotron anyone?) However, stopping an object from being added is quite a UI puzzle. Maybe instead of resetting everything, add a quicksave system? Holding Shift-S for 2 seconds (in case of accidents) saves, Shift-L loads. This way you wouldn't have to go back and wait for everything being added. Really depends on how you build systems. I like t=0 starting more, but it's quite complicated.

I feel that since asteroids are m=0 objects, they wouldn't have a collision area. Graphically, it seems they do, but they're basically test-masses right now. I support adding collisions, but it adds complexity for creating "real" massive asteroids, especially when they are at the scale of planets. Fixed stars seems like a bug; they merge with all things for me. (You do have merge on, right?)

Finally, I support position/velocity nudging, and we don't have any analogues right now; closest would be editing barycentric vectors. (I think it was actually suggested a while back, as something you could do with multi-select. Could use a button, since shift drag is already used for multi-select. Click the button, then click-drag (shift- for position) single planet or one of a selected group.).

tldr: Fix save/load with merge, think about t=0 trial and error button, asteroid merge, definitely add nudge for both planet and group.
NealCruco wrote:Welcome to the forums!
Andy has a downloadable version with these features, or at least most. It only costs $5.

(s)He might have the downloaded version, since none of those features are in the sim (or at least not exactly).
$1 = 100¢ = (10¢)^2 = ($0.10)^2 = $0.01 = 1¢ [1]
Always check your units or you will have no money!

NealCruco
Posts: 197
Joined: Thu Mar 27, 2014 8:26 pm

Re: Suggestions! (new)

Postby NealCruco » Sun Jan 18, 2015 12:27 am

@ARP
Well, their first point is that they want a S/L system that uses files instead of codes. That's in the newest downloadable version. But you're mostly right- I was underthinking.

User avatar
testtubegames
Site Admin
Posts: 1008
Joined: Mon Nov 19, 2012 7:54 pm

Re: Suggestions! (new)

Postby testtubegames » Sun Jan 18, 2015 1:50 am

SFastro wrote:Hi! I'm a physics & astronomy teacher - would love to use GSim for student projects! But I'm having trouble with these bugs / missing features:
...
I've tried a LOT of gravity simulators and GSim is the most promising for student use. Hope to see an updated version soon!

Hey there SFastro -- I'm so glad to hear you're interested in the simulator for your students! I'm all for doing that, and know that if I were a student I'd love to fling planets around myself. So, let me see what I can do about those problems you've been having...

-Saving and Loading: Yeah, this is pretty buggy at the moment. The ability to save is a brand new feature I posted last month, and it's very much in beta still. In the next update I'll try to fix the bugs and streamline it.
-Reset button for t=0: I like this. I find myself, too, wanting to repeat a setup a whole bunch, just changing one little thing. (aka 'experiments') Having a 'quick return' to a certain state would be very convenient. Maybe it's like the memory button on old calculators... where you click one button to save the state in some temporary memory slot... and click another button to jump right to it.
-Merge option for fixed stars and asteroids: Yeah, they should merge, too. This was just a matter of simplicity. (At the moment, all merging calculations are done in combination with gravity calculations, and since asteroids don't pull on each other, for instance, they don't collide.) But I'd like to get that in, assuming I can do it without too much of a lag hit.
-Changing positions and such with mouse: I'd love that, too. I agree this would make manipulating things a lot easier.

Thanks for sharing your suggestions... and if you think of any more, throw them my way. I'd like to get the next update to the gravity simulator up within the next month, and I'll try to address all these problems.

A Random Player wrote:Saving and loading are indeed quite buggy, but many of the problems I've noticed are because of merging; a "new" body resulting from a merge is saved in place of the old ones, which don't get saved.

Yup, that's a problem. The algorithm right now for making the save list is pretty basic. "What objects exist? When were they created? Cool... list them." This works pretty well, but leaves out any objects that have been destroyed due to merging/deletion/destruction. So ideally, I'd keep track of the deleted objects, too. That should fix the most glaring holes. (And if I save not only the initial states of objects, but the final states of them, then you'd be able to run a simulation backwards, too, and objects should reappear properly... unlike now).

ps - Neal and Random, thanks for being an extremely responsive welcome brigade to the forums! It's really nice to have you around.

NealCruco
Posts: 197
Joined: Thu Mar 27, 2014 8:26 pm

Re: Suggestions! (new)

Postby NealCruco » Sun Jan 18, 2015 10:09 am

testtubegames wrote:ps - Neal and Random, thanks for being an extremely responsive welcome brigade to the forums! It's really nice to have you around.


Either you're being sarcastic, or you failed to notice that SFastro had to wait four days for their welcome. That doesn't qualify as "extremely responsive" in my book.
And that reminds me: the email notifications are buggy. SF posted on the 13th, but I didn't get a "new post" notification until the 17th. That's not good.

User avatar
testtubegames
Site Admin
Posts: 1008
Joined: Mon Nov 19, 2012 7:54 pm

Re: Suggestions! (new)

Postby testtubegames » Sun Jan 18, 2015 11:13 am

NealCruco wrote:Either you're being sarcastic, or you failed to notice that SFastro had to wait four days for their welcome. That doesn't qualify as "extremely responsive" in my book.
And that reminds me: the email notifications are buggy. SF posted on the 13th, but I didn't get a "new post" notification until the 17th. That's not good.

Ah, nope, the problem was actually in the moderation queue. SF posted on the 13th, but it wasn't approved and visible until the 17th. So you two *were* quite responsive. Me, not so much. (In other news, I'll see if I can get emails about new posts by new users, it's kind of weird that I have to come and check -- and they are hidden in a user panel I don't normally open.)

SFastro
Posts: 2
Joined: Wed Jan 14, 2015 1:01 am

Re: Suggestions! (new)

Postby SFastro » Tue Jan 20, 2015 11:55 am

Thanks for the replies, everyone! I do feel like the forum is quite responsive. Andy, thanks for working on the improvements!

A Random Player
Posts: 523
Joined: Mon Jun 03, 2013 4:54 pm

Re: Suggestions! (new)

Postby A Random Player » Sun Jan 25, 2015 8:18 pm

More suggestions:
Polar grid. You could center it on an object/place/reference frame, to emphasize eccentricities and arguments of periapsis.


Precession view (or rather apsis view). Select two objects ("Primary" and "Tracked") and every time they go from going away each other to going toward, draw a dot on the second object selected ("Tracked"). Same vice versa. (Basically, draw a point at the measured apoapsis and periapsis.)
Examples of precession:

Code: Select all

Gravity Fun at TestTubeGames.com: [ForceGr: r^-2,xSet: 1.666667], [x0: 22.5,y0: 200,vx: -2.1,vy: -0.03,t0: 0,who: 3,m: 0,c: 0], [x0: 12.5,y0: 105,vx: -3.5,vy: -0.4,t0: 240.7998565,who: 3,m: 0,c: 5], [x0: 5,y0: 25,vx: 0,vy: 0,t0: 0,who: 1,m: 1000,c: 1], [x0: 27.5,y0: 27.5,vx: 0,vy: 0,t0: 0,who: 1,m: 1000,c: 1], [x0: 17.5,y0: 25,vx: 0,vy: 0,t0: 730.7995644,who: 1,m: 4294967296,c: 1]

Code: Select all

Gravity Fun at TestTubeGames.com: [ForceGr: r^-2,Zoom: 0], [x0: -83.18766,y0: -6.534039,vx: 0.8344933,vy: -9.217266,t0: 38.7999769,who: 3,m: 0,c: 0], [x0: 27.5,y0: 12.5,vx: 0,vy: 0,t0: 0,who: 4,m: 10000,c: 1], [x0: 140,y0: 27.5,vx: -1.240574,vy: 9.304306,t0: 0,who: 2,m: 10,c: 2,d: 300]

Code: Select all

Gravity Fun at TestTubeGames.com: [ForceGr: r^-2.1], [x0: 50,y0: 87.5,vx: -4.87,vy: 3.87,t0: 0,who: 3,m: 0,c: 0], [x0: -10,y0: 15,vx: 0,vy: 0,t0: 0,who: 4,m: 10000,c: 1]

*The first configuration might not be accurate if you only select one star - some kind of group thing would be needed.
**Ptolemy planet on the second
***Third is classic non-Newtonian force law. Relativity also produces precession. (Don't forget to change the law back!)
I'd imagine it would lead to an ellipse in the first example, cluster of points in the second, and circle in the third.
Additionally, there should be some way to show the direction of precession; I was thinking of drawing a circle at apoapsis and periapsis that shrinks everytime it is drawn (until a certain point, where it resets size), so they "point" in the direction of precession.

Interface might be hard - I can't think of a good one. Maybe create a separate list of draws? Allows for more versatility in trails and overlays, at the cost of increased complexity.


Additionally, a "resonance" (conjunction) view. Select 3 bodies ("Primary", "Inner", and "Outer"), and when body 2 ("Inner") passes between body 1 and body 3 ("Primary" and "Outer"), draw a line from body 1 to body 3. This allows you to see if a body is in resonance with another if lines stay in mostly the same place. See this gif but imagine a line being drawn each time a color flashes. This might be integrated with the apsis view interface mentioned above.
[overdrive]
Going with resonance, how cool would it be to be able to draw plots like this? (More here.) See also: this discussion on another gravity simulator.
The way these work is basically a long trail length displayed in a rotating frame, with a very large refresh timestep. In some cases (those with a circular orbit), we can do this with Lagrange tracking, but others won't work.

Side note: How cool would it be to have GSim used on Wikipedia, like the other sim?
[/overdrive]
Now the only problem is we need an actual example of a stable resonance...
$1 = 100¢ = (10¢)^2 = ($0.10)^2 = $0.01 = 1¢ [1]
Always check your units or you will have no money!

User avatar
testtubegames
Site Admin
Posts: 1008
Joined: Mon Nov 19, 2012 7:54 pm

Re: Suggestions! (new)

Postby testtubegames » Mon Feb 02, 2015 1:38 am

1. Polar grid - yeah, that's a nice one. I suppose the simplest way to do it would be to center it on an object you select. Though we could think about perhaps adding another non-physics object into the sim finally, so you could attach it to any origin you'd like. (We could also use this 'gravitationally transparent' object for adding comments into your sim, say)

2.Apsis view - I could see doing this. The question of whether distance has increased or decreased since the last frame would be easy enough to check (for some finite set of objects, naturally). Is there any reason people would need to know the direction of the precession? Generally you would be able to determine that by looking at the planet's path, or watching it move around a bit. And especially since it could precess around the central mass many times, I imagine any plan of 'ordering' the dots to get messy really quickly.

3. Resonance - Another cool one. Basically a way to watch out for eclipses, too. (Since this is a 2d world, man, are there a lot of eclipses!)

4. Weird plots - Hmm, I'm still trying to wrap my head around those gifs. There's indeed a large refresh timestep - and it appears to be on that pretty precisely matches the 'start' and 'end' of the orbital paths each frame. As in, the spirals don't have an obvious end point -- and they go around the center a very symmetric and eye-pleasing number of times. I wonder how they did that...

5. Your Wikipedia statement reminds me -- I really want to figure out some better ways of sharing what people have made. Right now, codes are great, but something like a gif-maker would be tremendous. The only trick is to give it a *really* *easy* *interface* in the sim. I'd love people to easily be able to make and share gifs (or movies, or screenshots, or whatnot).


Return to “Gravity Simulator”

Who is online

Users browsing this forum: No registered users and 2 guests