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Bob Marton

Question about Flight Simulation.....

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Albeit an unusual question, I was wondering if someone could shed some light on this:

In Flight Simulation (any flight sim platform), is my aircraft moving above the terrain, or is the terrain moving below my aircraft?

Thank you

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What do you mean? Usually, the frame of reference of the 3D engine is some fixed point in space, e.g. the center of the virtual earth (FlightGear, I think), or some point in the center of the currently loaded scenery area (I think X-Plane works this way). So, you could say that it is the virtual aircraft that is moving (i.e. changing its 3d coordinates) relative to the virtual terrain.

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I have often wondered about that. Because the airplane, in locked spot view, is fixed in the center of the screen it looks like it's the scenery that is moving and the airplane is stationary.

 

Bruce

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You guys think too much!

When you drive your car are you moving or is the ground?

Tell you what, fire up the simulator and take a flight and try not to hit the ground or have the ground hit you, whatever, your choice! :cool:

Kindest regards,

Stephen

Edited by SpiritFlyer
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It is not a question of crashing into the ground. It seems if you can sett LOD that the scenery is being drawn ahead of you, implying the scenery is moving and not the aircraft. This is further illustrated that if you pause the aircraft, the scenery continues to fill in ahead of you. I am sure that my question can be answered by a scenery or aircraft developer. 

Just interested inlearning about how the simulator works

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Just to clarify my interest. If the aircraft is what is moving, and not the planet below, then why is it that if I board my pmdg 737 under night skies, and do not leave the gate, eventually the sun will rise? In this case, the earth is moving, and the aircraft is along for the rotation.

Edited by Bob Marton

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6 minutes ago, Bob Marton said:

Just to clarify my interest. If the aircraft is what is moving, and not the planet below, then why is it that if I board my pmdg 737 under night skies, and do not leave the gate, eventually the sun will rise? In this case, the earth is moving, and the aircraft is along for the rotation.

How you read about theory of relativity lately? :laugh:

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37 minutes ago, lodestar said:

How you read about theory of relativity lately? :laugh:

Yes, i have a M.S, in Astronomy and Geophysics. Thank you.

but this is a simulation,  and your comments are not relative to the central question which was "when the simulation was developed was it programmed in a manner that the terrain moves under the aircraft or the aircraft moves over the terrain." The question was not about flight physics.

Edited by Bob Marton

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I am just speculating, but I would guess that all the simulation is done in the reference frame of the Earth's surface, which is assumed to be fixed. They probably at a Sun to this that moves on a given more or less circular trajectory around the Earth. So, the plane and the Sun would be moving, but not the Earth. My rationale for this assumption is that it would be a much more complex task to simulate a rotating Earth.

Peter

 

 

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I find too deep an understanding of the workings of the sim program lessens immersion. Kind of like a kid peeking down stairs on Christmas Eve and discovering Santa is just his Dad.😥 You deep thinkers make good things happen though.Like the Atom Bomb for example.

All meant in fun. Don't take that too seriously.☺

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27 minutes ago, Bob Marton said:

Yes, i have a M.S, in Astronomy and Geophysics. Thank you.

but this is a simulation,  and your comments are not relative to the central question which was "when the simulation was developed was it programmed in a manner that the terrain moves under the aircraft or the aircraft moves over the terrain." The question was not about flight physics.

Well, my comment was only partially a joke. I understand your question - only developers know, maybe. In any case, the plane and terrain relation is simulated, i don't know if they simulated earth movement or they just found a convenient way to make a illusion of this, but pretty much everything is taken care of(with some small inaccuracies), plane, earth, moon, sunrise etc. 

1 hour ago, Bob Marton said:

If the aircraft is what is moving, and not the planet below, then why is it that if I board my pmdg 737 under night skies, and do not leave the gate, eventually the sun will rise? In this case, the earth is moving, and the aircraft is along for the rotation.

Becouse does not matter how they simulated it, if you don't leave the gate, aircraft is not moving in relation to earth, but with earth, in relation to sun.

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1 hour ago, Bob Marton said:

Just to clarify my interest. If the aircraft is what is moving, and not the planet below, then why is it that if I board my pmdg 737 under night skies, and do not leave the gate, eventually the sun will rise? In this case, the earth is moving, and the aircraft is along for the rotation.

In most flight sims, the virtual earth is not moving (i.e. a certain point on the ground has fixed 3d coordinates). It is the virtual sun that is rotating around the virtual earth. Then, Coriolis equations should be added to account for the effect of Earth rotation (FlightGear does that).

Orbiter (space flight simulator) is an exception to this, as it uses the center of mass of the solar system as the center of its coordinate system.

 

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3 hours ago, PATCO LCH said:

You deep thinkers make good things happen though.Like the Atom Bomb for example.

All meant in fun. Don't take that too seriously.☺

You gave me a good laugh...best comment all week!

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3 hours ago, Murmur said:

Then, Coriolis equations should be added to account for the effect of Earth rotation

P3D/FSX/FSW doesn't emulate Coriolis, not sure about XP11 or AF2?

To answer the OPs question, neither is moving ... pixel colors are being set in a 2D coordinate system to provide the illusion of movement.

Cheers, Rob.

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18 minutes ago, Rob Ainscough said:

P3D/FSX/FSW doesn't emulate Coriolis, not sure about XP11 or AF2?

I think XP doesn't either, don't know about AF2. FlightGear does it (its academic roots show up in details like these).

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3 hours ago, Murmur said:

In most flight sims, the virtual earth is not moving (i.e. a certain point on the ground has fixed 3d coordinates). It is the virtual sun that is rotating around the virtual earth

Not sure, but it seems like earth is moving in MSFS based sims(at least this is accounted for in MSFS bubble arround you), just found this: https://msdn.microsoft.com/en-us/library/cc526981.aspx  

 Some interesting variables like: STRUCT SURFACE RELATIVE VELOCITY, STRUCT WORLDVELOCITY, STRUCT WORLD ROTATION VELOCITY...

24 minutes ago, Rob Ainscough said:

pixel colors are being set in a 2D coordinate system to provide the illusion of movement

I'm not sure... I belive you are using 4K display resolution?  Please don't let me bring quantum mechanics into discussion... :laugh: But ok, in the end, that's a great answer

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Did you all never program a game in Basic?

Or play Mario Bros?

Pretty sure the plane is "stationary". The rest is dressing.

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