[gdal-dev] create 25D MultiPolygon how to

[Mateusz Loskot]

legeochen wrote:
> Hi All
> I try to create some multipolygons with OGR. After creating them, but
> when I want view them in arcscene, it just make arcscene crash! Then I
> tried osgviewer with ESRI Shapefile, I was warned:
> ESRIShape loader: .dbf file containe different record number that .shp
> file. .dbf record skipped.

Inspect your shapefile with  ogrinfo as well as with
Shapelib's shpdump and dbfdump.
Check if .dbf contains exactly the same number of records
as .shp file

> Actually, only one feature in the dataset had been readed out.
> Then, I tried osgviewer with ogr, got warnings like this:
> Warning something wrong with a polygon in a multi polygon.

No idea what's osgviewer and what its errors mean.

>  for(Roadway::RoadWayArray::iterator itrw = _roadwayArr.begin(); itrw !=
> _roadwayArr.end();itrw++)

++itrw;

if you care about performance.

>  {
>   OGRFeature *poFeature;
>   
>   OGRMultiPolygon multiPoly;
>   poFeature = OGRFeature::CreateFeature(poLayer->GetLayerDefn());
>   Roadway::Triangle_list tris = (*itrw)->getTrianglelist();


No idea what Triangle and Roadway is, I assume it's your own geometry
type.

>   for(Triangle_list::const_iterator ittri = tris.begin();ittri !=
> tris.end();ittri++)

++ittri;

>   {
>    OGRPolygon polygon;
>    OGRLinearRing poRing;
>    poRing.addPoint((*ittri).a().x(),(*ittri).a().y(),(*ittri).a().z());
>    poRing.addPoint((*ittri).b().x(),(*ittri).b().y(),(*ittri).b().z());
>    poRing.addPoint((*ittri).c().x(),(*ittri).c().y(),(*ittri).c().z());
>    poRing.addPoint((*ittri).a().x(),(*ittri).a().y(),(*ittri).a().z());

Assure that

TRUE == poRing.get_IsClosed();

>    polygon.addRing(&poRing);
>    multiPoly.addGeometry(&polygon);
>    
>   }
>   poFeature->SetGeometry(&multiPoly);
>   if( poLayer->CreateFeature( poFeature ) != OGRERR_NONE )
>   {
>    printf( "Failed to create feature in shapefile.\n" );      
>    return false;
>   }
>   OGRFeature::DestroyFeature( poFeature );
>  }
>  OGRDataSource::DestroyDataSource( poDS );
> Any help is appreciated!! 

I'd suggest you to translate your Roadway/Triangle it to OGRPolygon
and OGRMultiPolygon (what you actually have done) and then dump it to
OGC Well-Known-Text (WKT).
Then, try to validate these geometries with PostGIS using
ST_GeometryFromText and ST_IsValid and friends.
See chapter 4 and 6 of PostGIS manual.
PostGIS (or GEOS) is good for geometries validation.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org