[vtkusers] shapefile reader

[Malcolm Drummond]

Hi

I've implemented a shapefile reader in Python as a vtkProgrammableSource which I'm planning to redo in C++ as a vtkPolyDataSource sometime over the Easter break. Problem is I only have files of type 1,3 and 5 (point, polyline and polygon) so currently I only have methods to reliably read these types. If anyone has multipatch shapefiles or shapefiles containing Z and/or optional M (measurement) data that I can use for development and testing PLEASE, PLEASE send me some (ie. anything other than vanilla point, polyline and polygon).

I'm going to make the reader freely available - I'll put in the vtk copyright etc. so if it's up to scratch (or can be made so) and the folk at VTK want to include it, I'll be more than happy.

For any potential-users / interested-parties here's my thinking so far ... 
uses separate method to read each main type (point, polyline, polygon, multipart - chosen after parsing the header) -hopefully if the format is extended (or as I get new types for the first time) it lessens impact on existing code. If present, Z data will be included in the points (otherwise Z = 0.0), M data as scalars in point-data. The id (record number) will be included as scalars in cell-data (facilitating look-ups into attribute-data on picking etc.). Polygons will require tessellation - I'm currently favouring the GLU built-in tessellator as it can handle the multipart polygons as is. For flexibility I think importing of attribute-data should be a separate issue - merging with attribute-data can take part down-stream if required. I was thinking a dBase reader could be provided later as a vtkDataObjectSource for those who don't want to connect to a database. Same goes for the shx indexing files - can provide reader later if need arises (provides position in shapefile of shape record based on id).

Any suggestions or disagreements most welcome.
Also, if there already is a reader and I've missed it, I'd rather feel stupid now than later.

Regards
Malcolm Drummond
GeoVision cc
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