Hi,
One more comment, your
objects should be numbered consecutively, starting from 0
Thanks a lot for the command on the numbering.
That’s a very good point!
When an OIF object
deforms, the origin definitely does not need to coincide
with the say center of the mass.
That is true, but so far no integration has be
done, so no deformation should have taken place.
Simply, the
triangulation mesh given in the
$fileNodes file is not centered around the
"expected" center of the sphere.
Probably, the mesh generator did not produced balanced
triangulation, which is in fact not a mistake.
That is what I thought. Anyway, I have never
produced a triangulation on my own. Is there any
recommendation of software/literature… you could give?
Greetings
Markus Wink
Dear Markus,
The switch "origin" in the oif_object_analyze command,
computes the average of the coordinates of the current
positions of the mesh points. When an OIF object deforms,
the origin definitely does not need to coincide with the say
center of the mass.
There is no wrong calculation in your script. Simply, the
triangulation mesh given in the
$fileNodes file is not centered around the
"expected" center of the sphere. Probably, the mesh
generator did not produced balanced triangulation, which is
in fact not a mistake.
One more comment, your objects should be numbered
consecutively, starting from 0. I strongly recommend to keep
this in mind. Normaly, the software should complain when you
do not do this, there will be a patch on this soon.
Ivan
Dňa 25.2.2014 15:02 Wink, Markus wrote / napísal(a):
Dear
all,
I have noticed a quite strange behavior in
the command “origin” for the OIF-implementation. Probably
somebody can help me out with that. In my script, I have
put a sphere in a channel at a specific position.
Afterwards I wanted to check, which result the command
“origin” gives. The interesting parts of my scripts are:
oif_create_template template-id 0
nodes-file $fileNodes triangles-file $fileTriangles ks
10 kb 10 kv 50
oif_add_object object-id 1 template-id 0
origin 15 15 15 rotate 0 0 0 part-type 1 mass 1
set x [oif_object_analyze object-id 0
origin]
puts $x
So I put the object with its origin @ 15 15
15; command “origin” prints out: 15.008655470737903
15.02980503816793 14.995383511450385
No integration of the system has be done so
far.
I can think of two reasons for the deviation:
1)
The source code is correct and the deviation
results because of rounding errors
2)
The template I have used (I used the
sphere_nodes/triangles.dat found on git hub) is somehow
not correct. Actually, I have noticed, that the points
given do not exactly fulfill the relation for a sphere
(x^2+y^2+z^2=r^2). So it could be that the deviation
origins from that artefact.
3)
The calculations performed by the command
“origin” has some error. Unfortunately, I could not
locate, where the calculation is performed in the source
code.
Does anyone have a clue?
Greetings
Markus Wink