mass = 1 ... Real weight equivalent ?

[Andy Gilbert]

Hi, just wondering if there is one. Only if your doing some physics math and equations which rely on real mass and weight distribution, then they obviously have a measurement in real life.

 

So...when i first thought about this i thought well, 1 = 1 in LE so i could make 1 be any measure i want... but that 1 in LE is dependent on LE's gravity and therefore sureley must have some sort of equivlent? no?

 

Thanks

Andy

[Scott Richmond]

I think the simplest answer would be to make it all relative. For example, if you have a 200KG iron ball and a 2KG book in a scene. Whatever you make the book in LE, lets say a mass of 4, then make the iron ball have a mass of 400.

[Andy Gilbert]

I think the simplest answer would be to make it all relative. For example, if you have a 200KG iron ball and a 2KG book in a scene. Whatever you make the book in LE, lets say a mass of 4, then make the iron ball have a mass of 400.

 

Yes i understand that, but... (an im not denying any of this as it might just be me getting all confused).. but say i have a ball thats 2KG in real life and i drop it from 2 meters then it will take a certain amount of time to get to the floor due to its weight and gravity.

 

So in LE... if i set my ball at 2m high in LE and set the mass to 2, will it fall the same? We dont know becase we dont know what 1 mass in LE is? It might be 1kg, 1g, 1ton?

 

Thanks

Andy

[Canardia]

From my experience how mass==1 objects behave in LE, it's very similar to 1kg objects in real life.

[ESP]

What is == ?

 

Robin

[Canardia]

It means comparison for equality. A single = would be an assignment.

[Andy Gilbert]

From my experience how mass==1 objects behave in LE, it's very similar to 1kg objects in real life.

Ok i thought i would be along them lines.

 

Im sure you know what i mean though as your doing a flight sim, to truly replicate a simulator, you find say a planes weight and mass of wings, fuselarge ETC and all forces depend on them values (mainly gravity)... so to replicate that in LE you need to be able to put the actual weight values in so the object "moves or translates" the same in LE as it would in real life.

 

Anyways.. i had a feeling from playing that it might be around 1kg to 1mass.

 

Thanks

Andy

[Marleys Ghost]

Yes i understand that, but... (an im not denying any of this as it might just be me getting all confused).. but say i have a ball thats 2KG in real life and i drop it from 2 meters then it will take a certain amount of time to get to the floor due to its weight and gravity.

 

So in LE... if i set my ball at 2m high in LE and set the mass to 2, will it fall the same? We dont know becase we dont know what 1 mass in LE is? It might be 1kg, 1g, 1ton?

 

Thanks

Andy

 

 

Have you tried looking over at Newton Game Dynamics to see what "rule of thumb" they use? they might have an answer I have not looked myself. Not sure if it would be a mass issue for your example of dropping a ball, as it would be a gravity value and air resistance/Drag issue, all objects, regardless of size or shape or weight,will free fall with the same acceleration in a vacuum.

[Andy Gilbert]

Have you tried looking over at Newton Game Dynamics to see what "rule of thumb" they use? they might have an answer I have not looked myself. Not sure if it would be a mass issue for your example of dropping a ball, as it would be a gravity value and air resistance/Drag issue, all objects, regardless of size or shape or weight,will free fall with the same acceleration in a vacuum.

 

yes in LE we can set r (air resistance) and drag. But gravity is set ( i know it can be changed) but to replicate any real simulation you want to able to input real values. So gravity value in LE will be the same as real life, so for an item to fall with a mass of 1... needs to have an equivelent measurement, surely?

 

And ill go have a look at newtons Game Dynamics, see if i can find anything.

 

Thanks

Andy

[Marleys Ghost]

yes in LE we can set r (air resistance) and drag. But gravity is set ( i know it can be changed) but to replicate any real simulation you want to able to input real values. So gravity value in LE will be the same as real life, so for an item to fall with a mass of 1... needs to have an equivelent measurement, surely?

 

And ill go have a look at newtons Game Dynamics, see if i can find anything.

 

Thanks

Andy

 

 

Nope, "regardless of size or shape or weight,will free fall with the same acceleration in a vacuum." The accelration is due to what ever value gravity has, the difference in an atmosphere is down to drag where size or shape will have an effect. Take a sheet of paper, and a ball, drop both .. the result is the sheet of paper falls far more slowly than the ball, now ...crunch the paper up into a ball and repeat.. both fall at the same speed ... you have not added any mass to the paper by crunching it up though.

[Marleys Ghost]

A better demonstration of "regardless of size or shape or weight,will free fall with the same acceleration in a vacuum." than my paper "crunching" .

[carlb]

lol Newton law

[Andy Gilbert]

Ok, i understand what your saying but im not sure if were drifting away from the original question.

 

Lets say.. we have the ball, paper what ever. The only force that has a value set in LE is gravity and that force is the same as the real world?

 

Ok... so from that imagine we calculated all equations and forces that would react on a 2 kg ball the size and shape of X. we can use all them real equations and values like air density ETC in LE because we are setting them none are preset, and at least one of them equations will rely on the mass of the object, which in real life we know is 2kg. In LE we can only give it pre-defined number that were not sure is in acccordance to all other values and measurements we have entered.

 

So for the example above, image you are einstien and all your equations are correct we have used all real life values what value would you put for mass in LE? how do we know mass(2) is 2kg and not 2g?

 

Cheers

Andy

[Marleys Ghost]

Ok, i understand what your saying but im not sure if were drifting away from the original question.

 

Lets say.. we have the ball, paper what ever. The only force that has a value set in LE is gravity and that force is the same as the real world?

 

Ok... so from that imagine we calculated all equations and forces that would react on a 2 kg ball the size and shape of X. we can use all them real equations and values like air density ETC in LE because we are setting them none are preset, and at least one of them equations will rely on the mass of the object, which in real life we know is 2kg. In LE we can only give it pre-defined number that were not sure is in acccordance to all other values and measurements we have entered.

 

So for the example above, image you are einstien and all your equations are correct we have used all real life values what value would you put for mass in LE? how do we know mass(2) is 2kg and not 2g?

 

Cheers

Andy

 

 

Without knowing how Newton uses this I get the feeling its arbitary .. SetBodyMass has a float value so you could make a distinction yourself 1.0 = Kg or 0.001 = g .. it will make no difference to say two oil drums with differing mass values dropped from the same height in the editor. But would have effect on say collisions between two oil drums with differing mass values.

 

As for equations in real life, you'd have to know just how newton works, and if it uses those at all I should imagine it is optimized for games not the lab.

[Andy Gilbert]

Ok, well thnx for the help and advise....I think we maybe thinking along to slighly different lines. But dont know how i can put it any other way.

 

I just cant see how, if i wanted to "try" and replicate the real wieght of and object to a simulated weight of an object in LE without knowing what 1 LE mass equates to is "truly" possible.

 

Anwyays... its not preventing me what what im doing, just trying to make it more realistic thats all, as when im researching forces ETC they all have a measurement that i can use in my equations, its just when it comes to weight... i dont "really" know what to set mass to? Even though i know the real weight measurement. I just play untill it "looks" right... which isnt very true simulation.

 

Andy

[Marleys Ghost]

I don't know if it uses a particular SI or CGS unit for its value system, most just seem to call it "a unit" and deifne it to "whatever" such as 1.0 = Kg or 0.001 = g

[Josh]

Default gravity in the engine is -9.8 units/s^2.0. Gravity on Earth at sea level is -9.8 meters/s^2.0.

 

Since you can change the gravity value, it's all relative, but I recommend using 1 unit = 1 meter. However, you should understand there is no such thing as real units in a computer program. One spatial unit could be an inch, a meter, a mile, or a light year. One weight unit could be a gram, a pound, or a ton. It's all relative.

 

Gravity affects all objects the same regardless of their mass. A piano and a feather will fall at the same speed in a vacuum.

[Flexman]

I used a mass of about 12 units for a 6 tonne helicopter which gives a pleasing result. Just scale your forces and torque appropriately.

 

 

But to be a little off-top, I keep seeing the misconception that hammers and feathers fall at the same rate in a vacuum. Which would be true if the objects didn't have mass. But a Hammer or Piano has a substantially greater gravitational field than a feather. They would actually fall faster, just not on a scale you would notice. But it's important if you plan on throwing large objects at nearby planets.

 

Apologies for the digression.

[carlb]

Flexman what you said is wrong or else the greats laws of newton would be wrong which have been a around a long time

[Canardia]

Actually Flexman is right, the gravitational pull makes heavier object fall faster. In addition there is no such thing as vacuum, as 90% of the universe is dark matter. Dark Matter has just the same kind of resistance as air, but of course much lower, so the shape and size of bodies matters also when they fall through dark matter.

[Porsche]

I've noticed you can also get a good grasp of the mass of certain objects if you place them above water and watch them float, and how they bounce upwards. I had a ship with way too low of a mass, and it would bounce out of the water and crash the editor. I thought it was funny, actually.

[TylerH]

Lumooja and Flexman are both right.

 

@Josh: Your gravity is set to 9.8*2, that is definitely not 9.8^2.

 

9.8 * 2 = 9.8 + 9.8 = 19.6

9.8 ^ 2 = 9.8 * 9.8 = 81.16

[Andy Gilbert]

And that is also what i was trying to get across, just not very well! (about the mis conception of the feather and piano.

 

And thats also an interesting find about the gravity in LE...

 

Andy

[Scott Richmond]

One thing to keep in mind here is that this is a game and you'll need to take into account what feels right. Just because you get the numbers right doesn't mean that when its played your 6 tonne plane will feel like a 6 tonne plane. By all means get the numbers close, but I would definitely spend some time seeing how things feel in-game as well.

[Pixel Perfect]

@Josh: Your gravity is set to 9.8*2, that is definitely not 9.8^2.

I think Josh was refering to units per second squared not 9.8 to the power of two, but I must admit I thought the default gravity setting was 9.8*2 not 9.8