Acceleration measuring

[KarateBrot]

Now that we have direct access to every object's velocity via readable(owner)).vel we can make an acceleration sensor in just 1 minute.

Open your console (F10) and declare some variables. Type in

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scene.my.acc := [0,0];
scene.my.vel1 : [0,0];
scene.my.time1 := 0;


Now to let the following code refresh itself put it eg. into controllerAcc in the object's script menu:

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{
    scene.my.acc = ((readable(owner)).vel - scene.my.vel1) / (sim.time - scene.my.time1);
    scene.my.time1 = sim.time;
    scene.my.vel1 = (readable(owner)).vel;
    11.000000
}


I really like it. I always wanted to have direct access to position and velocity because now practically there is no error while measuring.

Oh and don't worry when your acceleration variable displays [NaN, NaN] after stopping the simulation. The cause for this is simple. The code refreshes even if the simulation isn't running. So time doesn't fly by, meaning the difference between two timesteps is 0. So velocity's difference will be divided by zero. But as soon as you start the simulation again it will calculate properly again.

[daniels220]

Note that as of 2.0.1 beta, that you can embed this on an object without scene.my.* variables, and it will save.

You would go to the top of the script menu for that object, where there's a text field, and type:

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_acc := [0,0];
_vel1 := [0,0];
_time1 := 0;


Then modify the second codeblock to use those variable names.

Unfortunately you can't just put the dynamic variable directly on _acc, it doesn't seem to update all the time like it's supposed to. Still, your workaround of using ControllerAcc or whatever works just fine.

[KarateBrot]

yep i know. i forgot to say that so thanks for mentioning!
i often need the velocity or something else of an object in the global scope so i'm nearly always using scene.my. variables.

about the update thingy... did you try using (_acc) instead? i don't have 2.0.1 yet so i can't try that out.

edit:
i downloaded 2.0.1 but don't know what you mean. i tried it with _acc and it updates properly

edit2:
oh okay i get it. i know what you mean

[daniels220]

Just to be clear (especially for anyone else reading the thread...):

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_acc := {//code that calculates acceleration}


doesn't work.

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controllerAcc := {_acc = ... }


does.

[silversmart]

its great.... i like it... thank you karatebrot...
now i (and maybe other persons) can measure the speed without kilinchis k1probe...
i send you a scene in skype. with a little question... ^^

best regards bluebravo


btw i use algodoo 2.0.0

[KarateBrot]

well actually it's nothing special or new it's just the normal formula you can find in every physics book^^ i just wanted to post it because i like the precision of the values and the minimal amount of time you need to create it.

[hiltropper]

how do i adress "owner" ? is it the entity ID or should i type in e.this ?
thanks for answers

[Matten]

how do i adress "owner" ? is it the entity ID or should i type in e.this ?
thanks for answers

If you want to know the position of for example a box, you should use something like:

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scene.my.pos := (readable(owner)). pos

I think you can also use other words than owner, but I don't know them. In the newest beta version of Algodoo you can also get info from object by using the geom ID by using something like:

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scene.my.pos := (Scene.geomByID(31)).pos

Where the geom ID is 31 in this example.

[hiltropper]

ok , i thought "owner" was just for the example above thank you