Re: Program to visualize layers

"William L. Hibbard" wrote:

> > For iso-surfaces and fancier volume operations (like slicing), we need
> > to have a Linear3DSet.  This requires a regualr XYZ grid.  But we don't
> > have that grid readily available when our only data are the layers given
> > by Z values (and properties) on a requral xy grid.  To define the grid
> > for Z axis, I setup a z axis to have as many values as I have z values
> > on my layers, and defined a mapping of its index to the sorted layer z
> > values.  In this way, I can define a regular Linear3DSet volume and set
> > its elements using the layers data.  Ofcourse majority of this volume
> > data will be missing and so its a good idea to initialize the volume
> > elements to -1 first.
> If your data have Z as a function of (X, Y) it would be nice to find
> a way to solve your problem without using Fields with 3-D domains.
> Given a Field with MathType ((X, Y) -> Z) you can display it as a
> surface with the ScalarMaps X -> XAxis, Y -> YAxis, Z -> ZAxis.

That's exactly the problem I ran into when writing my program. When one
thinks of surfaces at some Z value, it doesn't necessarily have to be a
mapping like ((X, Y) -> Z). In fact, strictly spreaking it isn't,
because we eventualy have some, say, surface attribute A that's is a
mapping ((X, Y, Z) -> A). That is, in our examples surface water run-off
is a function of space. That's why I tried doing it with a  Linear3DSet.
And as I said, I left it with a 2D set because it worked.

> You can also use ConstantMaps to ZAxisOffset in the addReference call
> for each data object to create a set of stacked terrain surfaces.
> However, I'm not sure if this is what you want.

There are 2 things we want to do. First, we do want to develop a
programm like Mohamad's. But as he said, when it comes to geological
layers we'd run into trouble with the 2D Set (or am I wrong?). Correct
would be to use a 3D Set, because are also interested in slicing and
all. Secondly, we want to extend the DEMViewer to have 2 surfaces, but
not necessarily two geological layers. They might just be the same DEM,
each with its own attribute.

I'm not really sure what to use to do what! And "it works!" is not
really always a good judgement criterion. We also have quite a few
missing points, which break the continuous surface when we set them to
NaN. Unfortunately our domain is far from being rectangular. We are
basically dealing with river catchments.
In view of all of that, I cannot see how it'd be the best approach to do
what. I'm looking forward to seing Mohamad's approach to the problem.
Perhaps it could enlighten us a little bit.

Thanks again for the patience!


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