Universe Sandbox

Universe Sandbox Legacy => Universe Sandbox Legacy | Help => Topic started by: komatii on September 28, 2011, 07:25:24 PM

Title: Accurate accuracy mode is less accurate
Post by: komatii on September 28, 2011, 07:25:24 PM: It seems like the accurate accuracy mode is less accurate. As I increase the time step, orbiting bodies fly off into space much quicker with the accurate mode. Even with systems modeled off real world ones, such as our solar system, and earth and moon; normal mode seems to hold the orbits as stable for twice as long as accurate mode while steadily increasing the time step.

komatii
Title: Re: Accurate accuracy mode is less accurate
Post by: vh on September 28, 2011, 07:31:39 PM: this is because accuracy mode is slower and thus, it takes more time for your computer to calculate. So, when you speed both simulations up, the one with accuracy mode gets turned up to a higher timestep and is as a result, less stable.

Also, i think the accuracy only works on dust? i saw a notice in the sim about that or something.

but auto timestep is a great tool, just press "A"
Title: Re: Accurate accuracy mode is less accurate
Post by: FiahOwl on October 10, 2011, 07:36:42 AM: Quote from: mudkipz on September 28, 2011, 07:31:39 PM
this is because accuracy mode is slower and thus, it takes more time for your computer to calculate. So, when you speed both simulations up, the one with accuracy mode gets turned up to a higher timestep and is as a result, less stable.

Also, i think the accuracy only works on dust? i saw a notice in the sim about that or something.

but auto timestep is a great tool, just press "A"

Accuracy works on orbits.
Title: Re: Accurate accuracy mode is less accurate
Post by: vh on October 10, 2011, 08:23:00 AM: um, if you mouse-over the accuracy thing, it says something about applying only to dust, unless that has been removed/fixd
Title: Re: Accurate accuracy mode is less accurate
Post by: atomic7732 on October 10, 2011, 10:47:55 AM: Quote from: mudkipz on September 28, 2011, 07:31:39 PM
but auto timestep is a great tool, just press "A"
I believe there's a downfall there. Create two planets of any mass, one with an eccentric orbit (around 0.5) and one with any type of orbit outside of it (as long as it doesn't cross inside the inner planet's orbit at any time). Let the simulation run, and with auto-timestep the inner object's orbit gets circular.
Title: Re: Accurate accuracy mode is less accurate
Post by: vh on October 10, 2011, 11:04:30 AM: ugh, that reminds me of auto-orbit, i hate how the inclinations and eccentricities get messed up by that!

and also auto timestep messes up sometimes
if you had an orbiting body with high eccentricity, when it gets close to the other body, autotimestep can't slow it down fast enough and it slingshots off/does something wierd
Title: Re: Accurate accuracy mode is less accurate
Post by: dhm794 on October 10, 2011, 06:56:08 PM: This is made clear in the FAQ.
Title: Re: Accurate accuracy mode is less accurate
Post by: Dan Dixon on October 11, 2011, 07:37:04 PM: Quote from: komatii on September 28, 2011, 07:25:24 PM
It seems like the accurate accuracy mode is less accurate...

Good observation. Turns out the accurate mode (RK4) is less accurate at extreme speeds (when everything flies apart) than Euler mode, but more accurate at slower speeds.