Re: ogc features over orthophoto over dem

Hi Andrea,

> I prototyped around a little bit adding also shapefiles to my testcase
> and I must say: visad rocks!


> I have huge performance problems, which I hope to resolve somehow later.

Probably just big images over lots of topography

> I put the resulting screenshot at:

Looks great.

> I hope someone is interested in this first draft and has some ideas on
> how to do things better. I welcome all critics (Don Murray, I wasn't yet
> able to get things work following your advices, I will come back on that
> later).
> I have a couple of rather different questions I would like to post, in
> the hope they are not too scattered.
> - in visad, is there some kind of caching system that gives the
> possibility to work with huge files that can't be kept in memory? Kind
> of tiling mechanism. LIDAR and friends are a now used reality, has
> anyone experience?

Some of the file adapter, such as netCDF, do caching,
but the do not tile within a FlatField (i.e., not
within a single image). They do cache for multiple
images, such as in a time sequence.

> - in the image I made the river with a Gridded3DSet. I'm not sure if
> that is the proper way. Should I use some VisadLineArray?

Gridded3DSet is the proper way, since it is defined
in data space. a VisADLineArray is defined in display

> - also, I had to elevate the river of some meter, since in certain parts
> it went below the elevation model (which by the way is right, since the
> river is made of coarser points as the dem and the lines in some parts
> "intersect" the dem). Has anyone a better idea to overlay the shapefile
> over the dem?

The only alternative is to draw your river in your
texture mapped image.

> - I tried to simulate a line with borders by painting a thinner after a
> thicker one of different color. The result is weak as expected, is there
> any way to do styling of lines (apart of dashing, which I read is
> supported)?

You can set a limited number of line styles (i.e.,
in GraphicsModeControl, or by a ConstantMap to

> And last but not least (even if really not so important :)):
> - has anyone an idea about how to put a filled polygon over the dem? I
> tried as a joke to do it with Delauny, but it doesn't permit 3D.
> Perhaps the best would be to create an image and use it as a texture
> over the dem and photo (does this last sentence make a sense?).

Yes, construct a FlatField with MathType ((x, y) -> z)
and define your IrregularSet (i.e., Delaunay) as its
domain Set. Define the "z" range values of your FlatField
as the topo level (plus your fudge to keep them above
the image) at the corresponding (x, y) locations.

Good luck,

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