[Question] Collision detection

[Artlav]

Quote:

Originally Posted by dumbo2007

 Here is some code out of the blue and the class which handles that :

http://code.google.com/p/surface-phy...llider.cpp#592

                case CS_FROZEN:
                {
                        // Freezing not implemented yet, maybe just freeze the base
                        break;
                }

What will happen if i up the time acceleration while the DG is rolling across the terrain, or sitting on it?

[dumbo2007]

That piece of code is for freezing vehicles on Mars or any other planet when the focus is on some other planet like say the Moon. Thats because terrain generation is stopped for a planet thats not in focus. So I dont want to get wrong terrain data and try to apply it to a different planet etc etc.

Now the way I deal with time acceleration is this :

say 10x acceleration, I do 10 times more physics iterations before sending the final results to Orbiter, so the eventual output is correct. For 100x, 100 times more physics iterations. Now I have capped this currently at 10 times since otherwise things may slow down a lot (it may not, haven't tried it yet)

I cannot tell yet what adjustments I ll need to make for 100x + time accelerations. What I just tested right now was that as the time acceleration increases the collision mesh lags the DG by an increasing amount but this could be because I am not allowing Bullet to do higher that 10x iterations as of now.

I can still nearly force the DG into the position that Bullet is giving me till 1000x acceleration. Beyond that I may need to use attachment points and remove the Orbiter engine's control completely. Then apply all thrusts through Bullet.

But I haven't reached that stage yet. I am currently trying to figure out a general purpose collision mechanism for all default ships in Orbiter that's stable at 1x.

If the DG is sitting then it stays sitting at 10000x.

Bullet has support for continuous collision detection which needs to be turned on and may be a solution for high speed collisions. Haven't reached orbit yet, still working near the surface at normal speeds. Bullet wasn't designed for orbital speed collisions so may need to make some custom extensions there. We'll cross that bridge when we come to it. Probably sphere-sphere collision and loads of destruction should suffice . Even I can write such a routine.

[Artlav]

So, basically you're still fighting the Orbiter physics engine?
What about freezing at landing?
No reasonable amount of precision would make a vessel collide properly with proper terrain at 10000x or so - you'll have to freeze it somehow.
1x to 100x is rarely used in a space flight simulator.

I would have considered this part of the problem a priority - if it can't be done, no point figuring out the rest.

[dumbo2007]

Why would landing at 10000x be so important ? There is a lot of stuff that can be done in Orbiter that does not happen at 10000x.

[Artlav]

Quote:

Originally Posted by dumbo2007

 Why would landing at 10000x be so important ? There is a lot of stuff that can be done in Orbiter that does not happen at 10000x.

You landed a vessel on a planet, let it sit here, and switched to another vessel still in interplanetary space. Cue 100000x and first vessel being either properly freezed or shot into space.

[jedidia]

It seems to me the two of you are talking about two different problems. As far as I gather from dombo2007's post, he solved the freezing problem:

Quote:

If the DG is sitting then it stays sitting at 10000x.

What he seems to have trouble with is moving an object along the terrain at high time accel.

dumbo2007 seems to think that you are talking about detecting the collision at high time acceleration, not about freezing vessels that already "collided", so to speak...

[dumbo2007]

Yeah thats right, if a vessel is landed then it will stay landed at high time accelerations. Bullet does not apply any forces on it or alter any state vectors that causes it to be shot into space.

For a vehicle moving across the terrain, I ignore time accelerations beyond 10x because bullet can handle upto 10x accelerations. Maybe more I haven't tried. Or I just increase the number of physics iterations.

[Artlav]

Quote:

Originally Posted by dumbo2007

 Yeah thats right, if a vessel is landed then it will stay landed at high time accelerations. Bullet does not apply any forces on it or alter any state vectors that causes it to be shot into space.

That's good. The question i'm driving at is - how is it done?
The vessel is above the sphere, landed on the terrain, what makes it stay up?

Attachment points?
Extending touchdown points all the way to the surface?
Something else?

[dumbo2007]

Attachment points. I don't see any other way at the moment.

[Artlav]

Nice.
Well, good luck.
Orbiter do need working collisions at last.

[Tschachim]

Hi Artlav,

Quote:

Originally Posted by Artlav

 ...
MoonLand:
http://www.ibiblio.org/mscorbit/mscf...p?topic=1962.0
...

By the way, MoonLand isn't working with Orbiter 2010-P1 as denoted in the last post of the thread you linked. Any chance to get a rebuild/version working with 2010-P1?

Cheers
Tschachim

[BruceJohnJennerLawso]

With regards to surface Physics, I was wondering if there is anything that addon devs could include in their vessel code to support Bullet-collisions or will that be generic? I dont mind putting in the extra time if it means I can help with getting Orbiter collision detection working

[jarmonik]

Quote:

Originally Posted by jedidia

 Seeing that he is updating the ground collision model quite a bit currently, it might be possible that he intends to adapt it to be used with terrain, especially as he himself suggested a further separation of graphics client and terrain client.

Suggested ? Terrain client ? Well, I haven't heard.

[Xyon]

That's in the "Orbiter Dynamics News" thread. Well worth a peek.