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Hi,<br>
<br>
About the XYZ binding for better compression. In our research in the
NL escience center and TU Delft we have been thinking (not testing
yet though) about one possible approach for this.<br>
<br>
It is based on using space filling curves. So, once you have the
points that go in a block you could compute the morton/hilbert code
of the XYZ. Since all the points are close together such codes will
be extremely similar, so one could store only the increments which
could fit in many few bits. We have not tested or compared this with
any of the other compressions but we just wanted to share it with
you just in case you find it useful!<br>
<br>
An additional improvement would be to sort the points within the
blocks according to the morton code. Then, when doing crop/filter
operations in the blocks one can use the morton codes for the
queries similarly to what we presented in our papers with the flat
table (without blocks), I attach one of them (see section 5.2). In a
nutshell: You convert the query region into a set of quadtree/octree
nodes which can be also converted to morton code ranges (thanks to
relation between morton/hilbert curve and a quadtree/octree). You
scale down the ranges to increments (like you did when storing the
point of the block) and then you simply do range queries in sorted
data with a binary algorithm. In this way you avoid the
decompression of the morton code for most of the block. This
filtering is equivalent to a bbox filter so it still requires a
point in polygon check for some of the points.<br>
<br>
Kind Regards,<br>
<br>
Oscar.<br>
<br>
<br>
<div class="moz-cite-prefix">On 16-04-15 18:15, Rémi Cura wrote:<br>
</div>
<blockquote
cite="mid:CAJvUf_vVt+rSCU2A404dvXjxRP-Fj7+fQaCJoyix=2pxKRyQFA@mail.gmail.com"
type="cite">
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<div><span style="font-family:monospace,monospace">epic fail ! I
had avoided html just for you<br>
</span></div>
<div><span style="font-family:monospace,monospace"><br>
Dataset |subset size | compressing | decompressing |<br>
|(Million pts)|(Million pts/s)|(Million pts/s)|<br>
Lidar | 473.3 | 4,49 | 4,67 |<br>
</span></div>
<span style="font-family:monospace,monospace">21-atributes |
105.7 | 1,11 | 2,62 |<br>
</span>
<div>
<div><span style="font-family:monospace,monospace">Stereo
| 70 | 2,44 | 7,38 |<br>
<br>
</span></div>
<div><span style="font-family:monospace,monospace">Cheers<br>
</span></div>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2015-04-16 17:42 GMT+02:00 Sandro
Santilli <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:strk@keybit.net" target="_blank">strk@keybit.net</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex"><span
class="">On Thu, Apr 16, 2015 at 05:30:12PM +0200, Rémi
Cura wrote:<br>
> OUps<br>
><br>
> Dataset | subset size(Million pts) |
compressing (Million pts/s) |<br>
> decompressing (Million pts/s)<br>
> Lidar | 473.3 |
4,49<br>
> | __4,67__<br>
> 21 attributes | 105.7 |<br>
> 1,11 | 2,62<br>
> Stereo | 70 |
2,44<br>
> | 7,38<br>
<br>
</span>These tables aren't really readable here.<br>
Could you make sure to use a fixed-width font to write those
tables<br>
and to keep lines within 70 columns at most ?<br>
<br>
--strk;<br>
</blockquote>
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<br>
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<br>
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