Hi,

When you work with diferents nodes for the diferents elements, even if they 
have the same coordinates, DX interpolate the data between the nodes of the 
elements considering in this its neighbour. As the nodes of the elements is 
unique in your mesh, the interpolate will occur only inside of each element.

If you want a continous visualization you must have nodes shared between the 
elements.

On Quarta 02 Abril 2003 08:09 am, julien pommier wrote:
Hi,

I am using opendx 4.2.0, software rendering mode.
I guess there is something I didn't understand with opendx ordering of
nodes on a mesh composed of tetrahedra. I'm trying to export some data
which _may_ be discontinous across some tetrahedrons, and which is
piecewise linear inside. Hence, here is the data file for a very small
mesh of two tetrahedrons:

----------------------------------
object 1 class array type float rank 1 shape 3 items 8 data follows
0 1 0
0 0 0
1 0 0
0 0 1

0 0 -2
0 0 0
1 0 0
0 1 0

object 2 class array type int rank 1 shape 4 items 2 data follows
0 1 2 3
4 5 6 7

attribute "element type" string "tetrahedra"
attribute "ref" string "positions"

object 3 class array type float rank 0 items 8 data follows
0 1 0 0
0 1 0 0
attribute "dep" string "positions"
object "deformation" class field
component "positions" value 1
component "connections" value 2
component "data" value 3
end
----------------------------------
As you can see, nodes 0 and 7, 1 and 5, 3 and 7 are the same. The ordering
of both simplex is "direct". In this example the data is indeed continuous
this the value for node 5 and node 1 is the same.

Here you can see what I obtain if I do
"import->autocolor->showboundary->image":
http://www.gmm.insa-tlse.fr/~pommier/dx_wrong.png
(my .net is here: http://www.gmm.insa-tlse.fr/~pommier/dx_tetra.net ). As
you can see, the data is continuous but the coloring is not !

If I replace the nodes of the second simplex by "4 1 6 7" (so the
simplexes share the point which has a non-null value), then the result is
exactly what I would like:
http://www.gmm.insa-tlse.fr/~pommier/dx_right.png

I first thought it was a bad ordering of the nodes, but it is not the
case. Is this a bug in the renderer (the difference of color depends on
the viewing angle) ? Or should I try to avoid discontinuous data by
merging points who have same location and same data value ?

Thanks.

-- 
R.G. Damas

Universidade Estadual de Campinas
Faculdade de Engenharia Civil
Laboratório de Mecânica Computacional
+55 19 37882396

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