# velocity==NaN! & fixed=False

Hi, all
I make a facetbox with dynamic = true (fixed =False), and a error occured: velocity==NaN!
How can I fix this problem.
the mass of the box was already assigned

best regards

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2011-12-04
2011-12-05

> I make a facetbox with dynamic = true (fixed =False), and a error occured: velocity==NaN!> How can I fix this problem.> the mass of the box was already assigned

if you created the box from facets, it cannot have a mass, because
facets are always
non-dynamic bodies.

Without an example script is difficult to say, why you have velocity==NaN!
Anton

On Sun, Dec 4, 2011 at 5:20 PM, Alvin
> New question #180889 on Yade:
>
>
> Hi, all
> I make a facetbox with dynamic = true (fixed =False), and a error occured: velocity==NaN!
> How can I fix this problem.
> the mass of the box was already assigned
>
> best regards
>
> --
> You received this question notification because you are a member of
>
> _______________________________________________
> Post to     : <email address hidden>

 Alvin (lyj5300625) said on 2011-12-05: #2

and
O.bodies[-1].mass=20000
O.bodies[-2].mass=20000
....
to assign mass to them

and an error occured like " bodies 2230 has a velocity==NaN! " the body 2230 was part of the facetbox

but instead of creating a Box, no such error

> O.bodies[-1]
> O.bodies[-2]

As far as I know, indexes cannot be negative.

idx = O.bodies.append(utils.geom.facetBox( center=(5,5,5),
extents=(2.0,2.0,2.0)

in this case idx will have indexes of newly created facets.
Anyway, giving a mass to facets will not have an effect.
Facets will not move, for example, from gravity or interactions with
another bodies.

Anton

 Alvin (lyj5300625) said on 2011-12-08: #4

Thanks Anton
but the faccet can be move by force with the instruction in the Imposing condition of the manual, which write these
"Facets are case in the point: utils.facet makes them non-dynamic by default, as they have zero
volume and zero mass (this can be changed, by passing dynamic=True to utils.facet or setting
Body.dynamic; setting State.mass to a non-zero value must be done as well). The same is true for
utils.wall"

O.bodies[-1] really point to the last particle produced

And I try the above instruction and the facet move, but facets of a box did not interact with each other. So one can't apply some force on a single facet of the facetsbox.