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3 hours ago, Veld said:

Also planets don't spin as of now so its not an issue.

Does that make day and night cycles either 'cheating' or impossible? Come to think of it, I think I'd prefer to have fixed planets and light sources that move around them.... so I guess that's the 'cheat' I'd go with for days and nights.....

 

Edit: oops, @AzureSkye has already explained this well earlier in the thread: https://board.dualthegame.com/index.php?/topic/13258-physics-n-stuff/&do=findComment&comment=84713

 

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It causes big losds on the server.

 

Not even EVE Online had orbiting systems , which would be far simpler from a server stress level, uet they dont do it either.

 

Would love to know if there are any space mmos that do have planetary body system orbital mechanics - it cant be easy.

 

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To be fair the planets can be on rails. Assuming that relative coords are already being used so it can't be that hard to implement since all the voxels wold be as if they were stationery.

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Huh what about planet spin. I remeber NQ say it will spin(this is reason why we will not have space elevator ) but not rotate around the star.

Edited by ShioriStein

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3 hours ago, 0something0 said:

To be fair the planets can be on rails. Assuming that relative coords are already being used so it can't be that hard to implement since all the voxels wold be as if they were stationery.

That's not the problem. 

 

Problem is the system has to constantly check for collisions with ships and starbases

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3: Investigating torque and moment of inertia

What we know from pre-alpha footage

  • Much of what is said on torque can be found in this video
  • You can use RCS-like parts to torque your ship
  • Another part that is needed is a ‘gyroscope’
  • The angular acceleration in rpm/s is shown in the engineering report

wSDij4R.png

Deducing the nature of torque

It is implied RCS parts are separate in what mechanics apply to them. The guy in the video states: “they do not generate thrust; they generate torque”. In real life an RCS thruster is essentially just a thruster that uses alternate propellant. The only torqueing capability stems from its placement. However, in-game, what he says implies that the main thrusters only push the ship forwards and do not generate a torqueing force if the centre of thrust does not act through the centre of mass. The RCS is what does the torqueing. This is probably because if you’re ship was slightly asymmetrical your RCS would have to compensate a lot - especially for larger ships. This would be very punishing and constraining for designers; although this is just speculation.

 

A lot can be speculated about the gyroscope but not much said. It is implied the gyroscope acts as an orientation reference for the engineer report. This makes sense as the guy in the video states: “it tells the game where the front of the ship is” and “you don’t want to place it on the side”. You need to have a designated part to define the orientation of the ship as parts can be angled or there can be more than one of them.

 

It makes sense to have a designated centre of rotation as in an asymmetrical ship the centre of rotation would be way out and punishing for designers. It also makes sense because if fuel has mass then the pivot would change over time. If transferred, it can be exploited. But it's still unclear going by the footage and it is not actually stated that it is - which would be a pretty crucial point if it was.

Deducing the nature of moment of inertia

I’m not going to explain moment of inertia too in depth. But, in the real world, when you apply torque to an object each individual particle of mass has its own angular acceleration. The moment of inertia is a constant that describes the mass distribution of the object. It can be mathematically deduced for simple shapes and groups of simple shapes but it is very hard – if not impossible - to do so for anything more complex. So to predict the angular acceleration (which DU does) a calculation must be made. The question is: how.

 

Games like kerbal space program calculate the moment of inertia using a point mass system: all the parts of the ship are simply modelled as one infinitely small particle with a specific mass. This is a very simple way of dealing with things. Here is a model roughly describing what is going on in the video if this is the case:

 

2rZfhg1.png

The model is simplified to 5 separate shapes: The hull, cockpit, fuel canister and thrusters. The pitch, yaw and roll axes are in green, blue and red respectively.

 

3WlXqKJ.png

The cockpit is used for demonstrating how a point mass system for parts works to give the angular acceleration in the 3 axes. The orange dot is the location of the point mass, m. Each torqueing force, F, is coloured corresponding to the axes. The white line represents the perpendicular distance to the pivot, r (dependent on which axes.

The angular acceleration in each plane for the cockpit only is: UOcoctn.png (where α=angular acceleration and mr^2=moment of inertia for a point mass system)

 

To find the net angular acceleration for the whole ship you simply do: kUSdaw9.png for every part.

 

Alternatively, you can model the parts as simple shapes for a more realistic system. But this is rather unnecessary as custom built voxel structures, which make up a most of the ship, cannot be modelled as predefined shapes and have to be point masses.

About fuel depletion

Not much to deduce here. Only discuss. We simply do not know if it exists. If the fuel depletion and distribution on a vessel affects its mass then there are a 2 ways that can work:

  1. The point mass stays in place and it’s magnitude decreases
  2. The point mass shifts up and down the container according to a scripted formula to simulate drainage

Conclusion

  • A point mass system is the most likely method of calculating the moment of inertia
  • If you know the force generated by the RCS, you can design your own torqueing system. To convert angular acceleration from rpm/s to rad/s multiply by 2pi/60
  • Main engines probably do not generate torqueing forces. Just push where they point.
Edited by Veld
Updated 07/05/2018

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1 hour ago, Veld said:

It appears that the gyroscope acts as the centre of rotation for the ship. The guy in the video states: “it tells the game where the front of the ship is” and “you don’t want to place it on the side”. It makes sense to have a designated centre of rotation as in an asymmetrical ship the centre of rotation would be way out

The gyro just defines a reference plane, it does not define any kind of absolute position or axis of rotation. What determines the axes of rotation is either the weight distribution or the size of the construct, I'm not sure. But you can clearly see from the video that the ship does not rotate around the gyro, which is placed at the tail end of the ship.

 

So the location of the gyro makes no difference, only its orientation, and that's exactly what JC ("the guy in the video") says: "You can put it anywhere you want, but be careful not to orient it on the side like that or something, you have to really put it flat, in the front direction."

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4 hours ago, Nanoman said:

The gyro just defines a reference plane, it does not define any kind of absolute position or axis of rotation. 

Could you elaborate on 'reference plane'?

4 hours ago, Nanoman said:

What determines the axes of rotation is either the weight distribution or the size of the construct, I'm not sure. But you can clearly see from the video that the ship does not rotate around the gyro, which is placed at the tail end of the ship.

Don't know what you mean by clear as there is no clear reference point apart from the clouds on the horizon. But, yes, if you see exactly at this time just after he says "it flies pretty well..." the tail end raises a little relative to the cloud behind it as it pitches down. But even that is a bold estimation though as it disregards the drift of the vessel towards the horizon. I am puzzled as to how you came about this conclusion without using NDA prior knowledge.

4 hours ago, Nanoman said:

So the location of the gyro makes no difference, only its orientation, and that's exactly what JC ("the guy in the video") says: "You can put it anywhere you want, but be careful not to orient it on the side like that or something, you have to really put it flat, in the front direction."

He just says you can place it anywhere you want. I don't see how that implies it does not define a centre of rotation.

 

If you are right I honestly don't know what the point of the point of the gyro is then. To define direction? Why not use the direction of the seat? It just doesn't make sense to me.

 

Edit: actually thinking about it what you say makes sense. The gyro could just be used to define the orientation of the ship for the engineer report. If a ship has multiple seats, then which one decides the orientation? If it did define the centre of rotation, he would have probably said so as it is pretty crucial information. But going by the way the ship is moving in the video is still pretty unclear evidence as to the gyroscope not being the centre of rotation. I will update the post with this info regardless.

Edited by Veld
See edit

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19 hours ago, Veld said:

Could you elaborate on 'reference plane'?

A plane used as a reference for orientation. A plane in 3D space is defined by two 3D vectors that are perpendicular to eachother and parallel to the plane. A third vector is implied that is perpendicular to the plane. The gyro defines the forward and upward vectors by the placement requirements that JC mentions in the video.

 

19 hours ago, Veld said:

Don't know what you mean by clear as there is no clear reference point apart from the clouds on the horizon. But, yes, if you see exactly at this time just after he says "it flies pretty well..." the tail end raises a little relative to the cloud behind it as it pitches down. But even that is a bold estimation though as it disregards the drift of the vessel towards the horizon. I am puzzled as to how you came about this conclusion without using NDA prior knowledge.

I simply looked at the video. You'd be hard pressed to convince me that the ship rotates around its tail end. Extremely hard pressed. Like, if you would pay me a lot of money, I might say that I believe you just sothat I could get paid, but I still would not believe you.

 

Nothing I said here relies on anything other than what anyone can discern for themselves from that video you linked to (i.e. the pre-alpha ship building tutorial). The most you can say is that it may require some basic knowledge of 3D application programming to be able to reach some of these conclusions.

 

You go ahead and take another look at that video, just look at it, no need to overanalyze. Just look at how the ship flies and tell me with a straight face that it rotates around the gyro location at the tail end. If you can do that, then you can accuse me of breaching the NDA, and we'll take it from there.

 

19 hours ago, Veld said:

He just says you can place it anywhere you want. I don't see how that implies it does not define a centre of rotation.

Because then you could not place it anywhere you want. This is plain english we are speaking, not predicate calculus or legalese. He says you can put it anywhere you want as long as you are careful about its orientation. That means orientation matters, location does not.

 

Yes you can always place it anywhere you want, even to the side and pointing in the wrong direction. But that's clearly not what he meant.

 

19 hours ago, Veld said:

If you are right I honestly don't know what the point of the point of the gyro is then. To define direction? Why not use the direction of the seat? It just doesn't make sense to me.

Yes, the point of the gyro is to tell the game how the ship is oriented relative to the local coordinate system. They could have used any other element for it, but it would always impose unnecessary restrictions on how that element is placed.

 

For example some of their own ship designs that you can see in their videos and screenshots has the cockpit positioned at an angle. If the cockpit were used to determine orientation then everything would be off. The forward vector would point somewhat downward and the upward vector would point somewhat forward, and all those pitch/roll/yaw values in the engineering report would be useless because of it.

 

Furthermore different constructs can use completely different elements to make it flyable. The only element that they are guaranteed to have in common is the core unit, so that would be the only reasonable candidate to use as a reference for orientation, and some games do it that way, but there are still potential issues with it. Not to mention that not all constructs are necessarily meant to fly, not even all dynamic constructs.

 

So the easiest way to simply head off all kinds of problems like that is to make it into a separate element. This too is not inside knowledge (as far as I know), it's just common sense. There may be other reasons for their decision that I'm not aware of. Maybe it will tie into the skill system at some point, who knows. In any case there are plenty of predictable reasons to do it this way and I can't think of any reason not to.

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@NanoDot

I see you're point

 

It does indeed make sense for the gyroscope to define the orientation of the ship. But I am going to tell you with a perfectly straight face it is uncertain whether the gyroscope is the centre of rotation or not. Not saying it is. Not saying it isn't. It's not even right at the tail end as the thrusters hang over the edge. Not about to make a poll on this or complain about NDA either. However, I am inclined to side with you on this judgement as he does not mention the gyroscope is the centre of rotation which would be a crucial point to make.

 

I have updated the post with what has been said.

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1 hour ago, Veld said:

Edit: actually thinking about it what you say makes sense. The gyro could just be used to define the orientation of the ship for the engineer report. If a ship has multiple seats, then which one decides the orientation? If it did define the centre of rotation, he would have probably said so as it is pretty crucial information. But going by the way the ship is moving in the video is still pretty unclear evidence as to the gyroscope not being the centre of rotation. I will update the post with this info regardless.

Maybe it helps if you maximize the video on your monitor (phone might be too small). When you look at the ship flying by remote control, you can actually see the gyro location (on top of the core unit near the rear end) moving relative to the true center of rotation when it rotates. Also rotation around the gyro location would look very different, unnatural and unbalanced. Try to picture it and see how that would be different from how it flies in the video. Yaw is the most obvious one, pitch as well, roll not so much in this case. I'm not sure what more I can say. To me it seems quite obvious.

 

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19 hours ago, Nanoman said:

Maybe it helps if you maximize the video on your monitor (phone might be too small). When you look at the ship flying by remote control, you can actually see the gyro location (on top of the core unit near the rear end) moving relative to the true center of rotation when it rotates. Also rotation around the gyro location would look very different, unnatural and unbalanced. Try to picture it and see how that would be different from how it flies in the video. Yaw is the most obvious one, pitch as well, roll not so much in this case. I'm not sure what more I can say. To me it seems quite obvious.

 

Watched it fullscreen and I still don't see the anything. If it rotated at the gyro the only test to see if it was rotating there would be to observe that part staying still. Given how much it's jiggling about and how little it actually rotates there isn't much to say. I'm honestly 50/50 on this. 

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1 minute ago, Veld said:

Watched it fullscreen and I still don't see the anything. If it rotated at the gyro the only test to see if it was rotating there would be to observe that part staying still. Given how much it's jiggling about and how little it actually rotates there isn't much to say. I'm honestly 50/50 on this. 

Ok :)

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