<div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><div><br></div><div><br></div><div>Hi all, Regina,</div><div>working on removing CGAL as requisite for building pgRouting, so</div><div>aka rewriting pgr_alphaShape and pgr_pointsAsPolygon</div><div>using the example "S" found here:</div><div><a href="http://www.bostongis.com/postgis_concavehull.snippet">http://www.bostongis.com/postgis_concavehull.snippet</a></div><div><br></div><div><font size="2"><span style="font-family:sans-serif">As reminder, the alpha complex</span><span style="font-family:sans-serif">C</span><span style="font-family:monospace">α</span><span style="font-family:sans-serif">is a subcomplex of the Delaunay</span><span style="font-family:sans-serif">triangulation (</span><span style="font-family:sans-serif">DT</span><span style="font-family:sans-serif">)</span></font></div><div><font size="2"><span style="font-family:sans-serif">So no curves on the result (ST_concaveHull has results with curves, so its not an alpha shape)<br></span></font></div><div><br></div><div><br></div><div>This is the "face only" result I am getting using some alpha radius.</div><div>The yellow face are holes, and the red borders are the borders of the hole<br></div><div>The blue faces are "Singular" belong to alpha shape but there is no other face belonging to the alpha complex</div><div> that is adjacent to any of the face edges</div><div>The purple line are the borders of the alpha shape.</div><br><div><br></div><div><br></div><div><br></div><div><img src="cid:ii_jrp7m4ui0" alt="image.png" width="510" height="428"><br></div></div><div><br></div><div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><div>Interesting thing is that the alpha shape is a collection of geometries (polygon, line, point)</div><div>Its not just the border of the polygons.<br></div><div> </div><div><br></div></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">This is the "face + line" result I get using that alpha,</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">(that alpha makes all points to be on a line and or triangle, So right now there are not "lonely points")</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><br></div><br></div><div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><div><img src="cid:ii_jrp7q11y1" alt="image.png" width="530" height="453"><br></div></div></div><div><br></div><div><br></div><div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">So, currently pgRouting is returning things wrong, besides the fact that it should not deal with geometries,</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">the pgr_alphashape is not really returning an alpha shape information:</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">in form of a sequence of (x, y) it is defining polygons borders either external ring or internal rings of the polygons separated by NULL NULL</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">so its missing the lonely lines and the lonely points<br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">and pgr_pointsAsPolygon is transforming that to a geometry.</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">So to keep the same functionality aka not returning the alpha shape with lonely lines and lonely points, but only the polygon borders:</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">- The blue triangles are polygons on the result,</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">- Am I right on this statement?:<br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"> - yellow selection is a polygon with a hole, it can not have the triangle pointed by the arrow because it would be a self intersecting polygon,</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"> and the white area in the base of the arrow is really not a hole, looks like, but that area is just surrounded by 3 individual polygons</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">etc...<br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><div><div><img src="cid:ii_jrp8hqit4" alt="image.png" width="530" height="438"><br></div></div></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"><br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">I just want to make sure I am on the right track, and I have no concepts wrong.<br></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default"></div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">Regards</div><div style="font-family:arial,helvetica,sans-serif" class="gmail_default">Vicky</div><br></div><div><br></div>-- <br><div dir="ltr" class="gmail-m_176349504116719779gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><pre>Georepublic UG (haftungsbeschränkt)
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