<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">An advice to beginners:<div class=""><br class=""></div><div class="">1. Always check each scrap independently for “holes”. Such hole indicate incorrect position of walls according to base principle of drawing a map: The map is the projection of a passage to horizontal plane and the walls are borders of such projections. So there MUST NOT be walls inside (excluding walls with parameter “-outline none” for some reasons) the borders of such passage. Holes will produce mess in warping, joining and 3D models. They are incorrect in any way, because there is not unspecified rock (background) inside a passage.</div><div class=""><br class=""></div><div class="">Export map of a crap with these lines in layout to see the holes.:</div><div class=""><br class=""></div><div class=""><div class="">layout check_holes</div><div class="">symbol-hide group all</div><div class="">symbol-show line wall</div><div class="">debug station-names #for better orientation only</div><div class="">colour map-bg 85</div></div><div class="">end layout</div><div class=""><br class=""></div><div class="">export map …. layout check_holes</div><div class=""><br class=""></div><div class="">2. When there is a complicated situation to draw passage in one scrap divide the scrap to smaller ones just to simplify the process.</div><div class=""><br class=""></div><div class="">3. Always check two (or more) scraps to be joined for overlaps and continuity of walls of adjoining scraps before any joining.</div><div class=""><br class=""></div><div class="">4. A pit, a chimney or a hole among blocks is a gap to join scraps together too. But you should use manual joining point of line to point of line in such case.</div><div class=""><br class=""></div><div class="">Martin</div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="D63AA000-70B8-4B31-95F0-83AC446680D8" src="cid:58DC83EC-51EB-473E-831F-4A7B15C58B35" class=""></div></body></html>