[CIG-SHORT] Cell centroids

[Carl W Gable]

You can compute centroids of hex (or line, tri, quad, prism, pyramid, 
tet) with LaGriT.

You have to output the mesh in a format LaGriT can read (eg. Abaqus)

export abaqus "file_name" overwrite cubitids

I convert the abaqus to AVS format with the awk script below (script 
below is hardwired for quads).

Then the following LaGriT command compute the centroid and output it to 
a file in 3 column ascii.

read / avs / file_name_in / mo
createpts / median
dump / avs2 / file_name_out / mo / 0 0 0 2
finish

Cheers,
Carl Gable


          0          0          0          3          0
00003  1  1  1
xmed, real
ymed, real
zmed, real
   0.142157819824E+05  0.222367900391E+05  0.623520860076E+01
   0.143572114258E+05  0.222202792969E+05  0.708197271824E+01
   0.144949233398E+05  0.222228002930E+05  0.781360983849E+01
   0.146261022949E+05  0.222358046875E+05  0.813354587555E+01
   0.147520295410E+05  0.222421035156E+05  0.823126870394E+01


tessellate.lanl.gov:shell% cat abaqus2avs.awk
# this converts abacus quad file to avs
# awk -f abacus2avs.awk input.inp
#
BEGIN{ FS=","; ipt=0; iquad=0; IN_NODE=0; IN_QUAD=0; }
{

# look for key words
# *NODE, NSET=ALLNODES
# *ELEMENT, TYPE=S4R, ELSET=EB1

if ($1 == "*NODE") {IN_NODE = 1; }
if ($1 == "*ELEMENT") {IN_NODE=0; IN_QUAD = 1; }


if (IN_NODE==1 && NF==4) {
    ipt=ipt+1
    xic[ipt]= $2
    yic[ipt]= $3
    zic[ipt]= $4
    if ($1 == "**") {IN_NODE = 0}
   }

if (IN_QUAD==1 && NF==5) {
    iquad=iquad+1
    q1[iquad]= $2
    q2[iquad]= $3
    q3[iquad]= $4
    q4[iquad]= $5
    if ($1 == "**") {IN_QUAD = 0}
   }



} END {
   FS=" "
   print ipt, iquad," 0 0";

   for (i=1; i<=ipt; i=i+1) {
    printf(" %10d %14.4f  %14.4f  %7.4f\n",i, xic[i], yic[i], elev ) }

   for (i = 1; i <= (iquad); i = i + 1){
    printf(" %10d  1  quad %10d %10d %10d %10d\n",i, q1[i], q2[i], 
q3[i], q4[i] ) }
}

tessellate.lanl.gov:shell%


On 09/08/2012 08:33 PM, Matthew Knepley wrote:
> On Sat, Sep 8, 2012 at 9:29 PM, Birendra jha <bjha7333 at yahoo.com 
> <mailto:bjha7333 at yahoo.com>> wrote:
>
>     Hi
>
>     Does anyone know if it is possible to compute and output cell
>     centroid coordinates from CUBIT?
>
>     If not in CUBIT, is there some other tool (c++ code etc.) for this?
>
>     I need it for unstructured hexahedral grid. From google I found:
>     http://www.cs.berkeley.edu/~jfc/mirtich/massProps.html
>     <http://www.cs.berkeley.edu/%7Ejfc/mirtich/massProps.html>
>     which I tried to use but I don't understand why it does not work
>     for general hexahedron.
>
>
> The way that makes sense in PyLith is to take the middle point in the 
> reference element,
> (0.0,0.0,0.0) I believe, and transform it using the FE Jacobian 
> inverse for that point. We
> have these routines since they are used for point location.
>
>    Matt
>
>     Thanks a lot
>     Birendra
>     _______________________________________________
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>
>
>
>
> -- 
> What most experimenters take for granted before they begin their 
> experiments is infinitely more interesting than any results to which 
> their experiments lead.
> -- Norbert Wiener
>
>
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-- 
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
Dr. Carl W. Gable, Staff Scientist

Acting Group Leader, EES-16, Computational Earth Sciences
MS T003, Los Alamos National Laboratory, Los Alamos NM 87545
Email:gable at lanl.gov   Voice:505-665-3533   Fax:505-665-8737

Homepage:                         http://www.ees.lanl.gov/staff/gable
LaGriT Mesh Generation Software:  http://lagrit.lanl.gov
Mesh Generation, Geological Apps: http://meshing.lanl.gov

Focus:Geophysics, Hydrology, Mesh Generation, Computational Geometry

Schedule B
/\/\/\/\/\/\/\/\/\/\/Correspondence / TSPA\/\/\/\/\/\/\/\/\/\/\/\/\/

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