[Gdal-dev] OT: Shapefile's multipatch

Paul Selormey paulselormey at gmail.com
Sun Oct 29 17:41:46 EST 2006

Hello Frank,
Thanks for the mail and the information.
I am currently trying to implement a shape geometry reader/writer similar to
WKT/WKB readers/writers as part of my .NET port of JTS.
However, I wanted to make it very complete and therefore started looking for
information on the multipatch - currently no open source project I know includes
the support.

I do not have any data for testing yet, I am actually also looking for
some. So far,
there is a Geotools patch for multipatch that includes some data. However, the
patch does not support the triangle fan and strip and therefore does not include
any search test data.

Please can anyone on the list with experience in this field help with the data,
may be create them with ArcView for testing?

Best regards,

On 10/30/06, Frank Warmerdam <warmerdam at pobox.com> wrote:
> Paul Selormey wrote:
> > Please I need help in understand some aspect of the multipatch format
> > of the shapefile.
> > In particular, I want understand some points on
> > 0. triangle strip
> > 1. triangle fan
> >
> > The question is: Does the "NumParts" includes the number of triangles
> > in the strip or fan? (my own understand is that it does NOT, but wish
> > to confirm, just in case!).
> Paul,
>  From reading the specification it seems the NumParts does not
> address the number of triangles in a strip or fan.  Rather it
> indicates the number of parts, each part potentially being a
> triangle strip, triangle fan, outer ring, inner ring, first
> ring or plain ring.
> I don't actually have much first hand experience with multipatch
> data.  When I have encountered it I think it was typical for each
> shape to be a single part, either a triangle strip or a triangle
> fan.  But I don't recall details.
> If you have a couple not too large, but "real world" multipatch
> examples that are redistributable, I'd love to have a copy.
> Best regards,
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | President OSGeo, http://osgeo.org

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