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Re: Sign convention or name O.energy['gravWork']
I feel like it is a question of perspective, and undecidable overall.
Is it work by gravity or work against gravity? You can find the two
meanings easily. It's still a work in both cases.
OTOH it seems these energies are underdocumented overall. I did not find a
list of available energies anywhere in the doc.
I must say trackEnergy=True is slow. It computes many un-needed things
(gravitational work is a good example, why should we increment G-=g*vel*dt
at every iteration while we can get at any point in time -g*pos? same issue
with elastic work).
In current design I would not recommend it although it is elegant and handy
for quick tests.
On Mon, 20 Apr 2020 at 16:13, Jerome Duriez <jerome.duriez@xxxxxxxx> wrote:
> I now think the most logical would be to keep this expression with a
> minus sign [*], but rename 'gravWork' into 'gravPotential' (like we have
> It would reconcile for me the name with the coded expression, and be
> more logical with the existence of O.energy.total() function (which sums
> all terms in O.energy and certainly is expected to be constant)
> Thoughts ?
> Chargé de Recherche / Research Associate
> Inrae, RECOVER
> 3275 route Cezanne – CS 40061 13182 Aix-en-Provence Cedex 5 FRANCE
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> On 20/04/2020 10:25, Jerome Duriez wrote:
> > Hi,
> > Is there a consensus (outside myself) for the extra minus sign in
> > O.energy['gravWork'], computed in NewtonIntegrator at [*].
> > It seems that code line was initially introduced by Vaclav in
> > GravityEngine in commit [**] (and made finally its way into
> > NewtonIntegrator).
> > As far as I'm concerned, I can not make sense of the comment justifying
> > that sign, just above [*], neither of a consequent negative power of
> > weight during some free fall.
> > Jérôme
> > [*]
> > [**]
> > see also corresponding file from that time at
> > ------
> > Chargé de Recherche / Research Associate
> > Inrae, RECOVER
> > 3275 route Cezanne – CS 40061 13182 Aix-en-Provence Cedex 5 FRANCE
> > +33 (0)4 42 66 99 21
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