Julien,

I my knowledge is not so deep about this topics, but is some thing like you 
have written "I guess it is a problem with opendx treating each (red) simplex 
as if no other simplex were present when it computes the lightning".

best regards!

On Quinta 03 Abril 2003 02:05 pm, julien pommier wrote:

Well I admit my first mail was not very clear ;-) I am well aware of what
you're saying. I'm producing dx files whose data is often discontinuous.
So I don't what to enforce its continuity, hence, as you say, I am using
different set of nodes for each simplex of the mesh. But my test-case was
just to see what is displayed when the data is indeed continuous (the two
nodes which share the same location are assigned the same value), and the
result is not what I expected to see, since the displayed colors are not
continuous across elements!

It looks like a rendering bug, the variation of colors depend on the
lightning angle. It may be clearer on the following example:
http://www.gmm.insa-tlse.fr/~pommier/dx_donut.png

The data that I am trying to represent on this donut is continuous, but it
has been exported as a discontinuous one on a finite element mesh (red
edges). In order to represent high order finite elements, each simplex of
the mesh is refined (the yellow edges). Since the finite element base
functions are continuous, the refined tetrahedra share their nodes inside
each element, but the red tetrahedra do not share there nodes with others.

As you can see, the result is strange: the color are right inside each
element, but they are too dark near the red edges.

So I guess it is a problem with opendx treating each (red) simplex as if
no other simplex were present when it computes the lightning or something
like that.

-- 
R.G. Damas

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

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