Projected Area of clump

Hello Sergio,

What particle shapes do you use for your clumps? Could you please explain
more in detail what do you mean by projected area of several clump?

I checked the utils.perpendicularArea function very quickly, but could not
find out how it works..

b1,b2=utils.sphere((0,0,0),1), sphere((1,2,3),2)
O.bodies.append((b1,b2))
perpendicularArea(0) # result = 30
perpendicularArea(1) # result = 24
perpendicularArea(2) # result = 20

Thanks for the answer and hopefully we can iterate until your question is
answered :-)
cheers
Jan

2013/9/2 Sergio <email address hidden>

> New question #235031 on Yade:
> https://answers.launchpad.net/yade/+question/235031
>
> Hello,
>
> I am a very new Yade user, and I'd like to post my problem as I know that
> there are some Yade experts here that could advice me ;).
>
> I need to calculate the projected area (respect to the axis) of several
> clumps of my calculation. But I really don't know if there is an
> instruction to do that, or how I would have to proceed. I'm looking for
> doing the same as 'yade.utils.perpendicularArea(axis)', not with spheres,
> but clumps.
>
> Thank you for your support.
>
>
> --
> You received this question notification because you are a member of
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Hello Jan,

Thank you very much for your feedback. My clumps are made from overlapping spheres of different radius (15-30 mm). From what I've understand reading the yade's doc, the 'perpendicularArea' has meaning only with spheres bodies.

So, If I made a clump of several overlapping spheres, I understand that the utility is not valid.
Appart from that, how can I check how the 'utils.perpendicularArea' works? I have to say that I work with yade-daily, but I downloaded the 'trunk' folder. Am I rigth looking for the the utility in this folder?

As you can say, I'm totally lost. But I'll keep trying. Thank you for your time and help ; )
Sergio

Hello Sergio,

 So, If I made a clump of several overlapping spheres, I understand that
> the utility is not valid.
> Appart from that, how can I check how the 'utils.perpendicularArea' works?
> I have to say that I work with yade-daily, but I downloaded the 'trunk'
> folder. Am I rigth looking for the the utility in this folder?
>

From what I sent in previous email, I really have no clue what the function
perpendicularArea does.. It has almost no documentation and the results I
sent are a bit wild.. So from my point of view it is not valid even for
spheres themself :-)

If you want to look something in the source code, you can use the
downloaded trunk version (as you already mentioned), or you can use
launchpad [1].

I think your question should not be difficult to answer or to implement a
new function for you (as you use yade-daily, you could use it almost
imediatelly). The only problem is, that I don't know exactly what you mean
by "projected area (respect to the axis) of several clumps" (at least I can
imagine more meanings of that). Could you maybe draw a simple sketch and
place it somewhere to the internet with the link in next email?

Thanks
Jan

Hello Jan,

Thanks again for your quick response. To clarify what I mean with projected area, I point to a representative image I found in the internet:

http://www.real-world-physics-problems.com/images/physics_skydiving_8.png

I hope that the figure helps to understand what I mean : )
I will continue to understand a little bit more the function that Yade uses now, beginning by founding it in the trunk version.

Thank you
Sergio

Hello Sergio,

> http://www.real-world-physics-
> problems.com/images/physics_skydiving_8.png
>
perfect, exactly what I meant :-)

>
> I hope that the figure helps to understand what I mean : )
> I will continue to understand a little bit more the function that Yade
> uses now, beginning by founding it in the trunk version.
>
you can find the function in yade/py/utils.py file. It uses aabbExtrema
function inside, which you can find in yade/py/_utils.cpp file.

Now back to your problem. One thing came to my mind, you can estimate the
projected area by defining a grid and checking if the point of the grid is
contained by your clump or not. Along what axis you want to make the
projection? x/y/z or some generic axis?

Would you like to try to implement it, or should we help you by
implementing such function in Yade?

cheers
Jan

Thank you again, Jan ; )

With all the clues that you have given to me, I will try to face the problem for myself, but I'm sure that I will continue asking questions referring to it.

>you can estimate the
>projected area by defining a grid and checking if the point of the grid is
>contained by your clump or not. Along what axis you want to make the
>projection? x/y/z or some generic axis?

I think you are considering to do something like is done in mass inertia approax in clumps, right? It could be an option... I will think about it. ; )
I will share my progress referring to the problem.

Thanks
Sergio