[pdal] filter on return value

[Luca Delucchi]

On 4 June 2015 at 15:11, Howard Butler <howard at hobu.co> wrote:
> Luca,
>

Hi Howard,

> Yes these two are somewhat overlapping in functionality, but the predicate filter is much more powerful in exchange for being a bit slower and definitely more complex.  The intention is that filters.range is for when you can do simple attribute-based filters, and predicate/programmable are for when you want to do something with complex logic without having to write an entire filter in C++ to do it.
>
> The problem with  --last-return-only is that it is a complex expression that means, “keep points where ReturnNumber==NumberOfReturns”. You can’t do that in a single filters.range invocation. You instead would have to make a filters.range for each last return combination, and then filters.merge them altogether afterward.
>
> See https://github.com/PDAL/PDAL/blob/master/test/data/plang/predicate-keep-last-return.xml.in for an example of how to use the predicate filter to keep last returns.
>
> Hope this helps,
>

yes sure, it was really useful.
Can I mix filters.predicate and filters.range right?

> Howard
>


-- 
ciao
Luca

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