Re: ogc features over orthophoto over dem


Andrea Antonello wrote:

I have huge performance problems, which I hope to resolve somehow later.
Probably just big images over lots of topography

Yes, it is that, but there is no way to deal with it (sorry: I know no
way). The resampling to merge the flatfields brings the dem to the
resolution of the photo, which is always high resolution. Some texturing
would be for sure more performant.

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

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?
I'm currently using LIDAR and CLOUDSAT data in the IDV and HYDRA.

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.

Alright, someone in the list working with big datasets? Is there a
different solution?
I have plans to do this for large images - the logic to handle textures larger
than the graphics limit will have alot todo with this.


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

I'll have a deeper look into it. Does this include also lines with

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.

I'll try that out soon. I'll post the results.

Thanks for your help.


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