I have a series of polygons which overlap in spatialite. Each has a an attribute providing it's z-order as well as the output color for that polygon. What do I need to do, processing-wise, to allow SharpMap to display the polygons based on z-order, along with the proper color for each polygon, all in a SINGLE layer?


You would first need to tweak the SpatiaLite provider by either

  • add a OrderBy property and apply that to the relevant queries (GetGeometriesInView, ...), or
  • update the provider to handle spatial views correctly.

Then you need to apply a custom theme setting assigning the appropriate color in respect to ZOrder.

Why don't you want several layers?

Hth FObermaier

  • Thank you for the informative response. Custom theme is no problem. I will have a large number of layers if I did not preprocess the data. I need a very fast rendering methodology for the sharpmap part of the process and I'm trying to avoid cutting up the polygons so that only the non overlapping parts are available in the layer. – WayneF Feb 17 '12 at 23:37

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