[pdal] Reading and Writing outside of a stage

[Andrew Bell]

On Mon, Jul 17, 2017 at 10:29 PM, Jason Beverage <jasonbeverage at gmail.com>
wrote:

> Hi all,
>
> I'm new to PDAL and I'm currently porting an existing point cloud tookit
> we have at Pelican Mapping to use PDAL instead of LASTools and I had a
> couple of questions.
>
> Our toolkit is similar to Entwine in that it takes a large number of input
> points from LAS/LAZ files and chops them up into tiled LAZ files with the
> goal of displaying them in OpenSceneGraph and osgEarth based applications.
>
> Since we're dealing with a huge number of points, I'm making heavy use of
> streaming so I can avoid keeping the entire dataset in memory.
>
> For reading, I found the StreamCallbackFilter so I can intercept the
> points coming from a stage and process them one by one as I was doing
> before, so I think that will work for my case.
>
> For writing however, I'm running into a bit of snag probably due to my
> lack of understanding of the streaming API.
>
> We basically have an algorithm that does something like this:
>
> for each point in all the input points:
>     // Figure out which output file to write the point to based on it's
> location.
>     Writer* writer = getWriter(point);
>     writer->writePoint(writer);
>
> So we create a bunch of output writers (using LASTools) based on an octree
> split, and for each point we determine which writer to write to and write
> the incoming point to the appropriate output file.
>
> Is there a simple way to write points interactively to a Writer?  It seems
> like if the write functions of Writer were public that it would be fairly
> easy to implement something like that.
>

I'm not sure I understand exactly.  You can create your own stage that
implements processOne() and do anything you like in it.  There is nothing
particularly special about a writer.  It's just a stage.  There's no reason
you can't chain a bunch of StreamCallbackFilters together if that's helpful
-- the first one could do whatever you're doing now, the second one could
do the writing you want to do.  Or they could be combined.

Is part of what you are wanting is to use PDAL's LAS writer instead of
LAStools?

-- 
Andrew Bell
andrew.bell.ia at gmail.com
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