Particle mass should not be on org.geppetto.core about org.geppetto.core

[tarelli]

It should be read from the file, not being a constant at all.

[gidili]

It's used to calculate at least another derived constant that's the same
for all particles (its called "delta"). I am not even sure it's the
particle mass.

Sent from my iPhone

On 24 May 2013, at 15:33, Matteo Cantarelli [email protected]
wrote:

It should be read from the file, not being a constant at all.

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[tarelli]

if the mass is not constant any other information derived from it is not constant either, unless we change the schema to define a group of particles which share the same mass we should be doing the same operation for as many particles as there are (and if needed to optimize that by caching the risult for a given mass for instance). If it's not the particle mass and it's a constant of the algorithm then we should change its name to reflect that and stil move it out org.geppetto.core. Note that there is a mass attribute for a particle in the schema.

[gidili]

That MASS is a constant - that's all I know.

Again, I dont know if thats the mass of a particle and even if it is It
doesn't make any sense to calculate the delta for every particle because
its the same delta for the entire system. What do you do if particles have
a different mass?

@a-palyanov should be able to clarify.

[tarelli]

Well I would imagine that it's not a given that every particle in the system would have the same mass. Particles with different masses would exert different forces I assume but it's pointless to speculate if we are not even sure if that's the mass.
@a-palyanov could you wave in?

[gidili]

I am only saying its a constant in the C++ version. That's all I know :)

[gidili]

Regardless of this discussion about mass - should all those PhysicsConstants be moved to model.sph? They really don't belong in core...

[a-palyanov]

It is possible to implement different masses, but it will require writing
of some additional code, which maybe quite difficult (Solenthaler's
dissertation contains a chapter or even two describing it).
In my opinion for OpenWorm purposes common mass value (but particles with
different properties, like solid, liquid, elastic, muscle etc.) will be
enough and will not limit us anyhow.

A.

2013/5/24 Matteo Cantarelli [email protected]

Well I would imagine that it's not a given that every particle in the
system would have the same mass. Particles with different masses would
exert different forces I assume but it's pointless to speculate if we are
not even sure if that's the mass.
@a-palyanov https://github.com/a-palyanov could you wave in?

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[gidili]

I moved all this stuff into org.geppetto.model.sph: openworm/org.geppetto.sibernetic@a31e807

We can consider moving some of the actual physics constants back into core but for now we can consider everything as an SPH constant.