Line-based building (Water Overlay) - Revision history

Rudolf@tygron.nl at 14:21, 11 February 2026

2026-02-11T14:21:54Z

← Older revision		Revision as of 14:21, 11 February 2026
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	</ul></div>		</ul></div>
	Generally, this kind of polygon is undesirable for a line-based building, since it will generate a skeleton with many end points.		Generally, this kind of polygon is undesirable for a line-based building, since it will generate a skeleton with many end points.

			===Direction===
			For some structures, a direction is relevant to determine from which location to which location water flows, and to relate any output attributes related to properties on either side of the [[Building]]. Particular types of structures may have their own rules for determining their "direction" as such. If those rules are absent (such as for a culvert), or unclear (such as based on higher of 2 water levels, but both water levels are the same), the direction is determined based on the computed skeleton line of the structure.

			Although the {{software\|client}} does not directly show which end of a structure is which end, the underlying data including the skeleton line can be accessed via the API representation of the [[Building]]. Of the [[Building]]'s skeleton line, the first coordinate is the first side (or side A) and the last coordinate is the second side (or side B).

	==General advice==		==General advice==

Maxim@tygron.com at 11:34, 5 October 2022

2022-10-05T11:34:54Z

Maxim@tygron.com: Created page with "Line based buildings are constructions for which their geometry is interpreted as a 2 dimensional line with two end points. Examples of line based buildings are the following hydraulic structures: {| {{STDT|overlay sortable}} |- ! style="width:50px" | Icon !! style="width:100px; text-align:left;" | Name !! style="text-align:left;" | Name |- |style="text-align:center;"|25px |Culvert |Flow in..."

2022-10-05T09:25:57Z

Created page with "Line based buildings are constructions for which their geometry is interpreted as a 2 dimensional line with two end points. Examples of line based buildings are the following hydraulic structures: {| {{STDT|overlay sortable}} |- ! style="width:50px" | Icon !! style="width:100px; text-align:left;" | Name !! style="text-align:left;" | Name |- |style="text-align:center;"|25px |Culvert |Flow in..."

New page

Line based [[Building|buildings]] are constructions for which their geometry is interpreted as a 2 dimensional line with two end points.

Examples of line based buildings are the following hydraulic structures:

{| {{STDT|overlay sortable}}
|-
! style="width:50px" | Icon !! style="width:100px; text-align:left;" | Name !! style="text-align:left;" | Name
|-
|style="text-align:center;"|[[File:Waterwizard_icon_culvert.png|25px]]
|[[Culvert (Water Overlay)|Culvert]]
|Flow in both directions possible.
|-
|style="text-align:center;"|[[File:Waterwizard_icon_weir.png|25px]]
|[[Weir (Water Overlay)|Weir]]
|Conditional flow, based on the weir's height. Flow possible in both ways.
|-
|style="text-align:center;"|[[File:Waterwizard_icon_pump_q.png|25px]]
|[[Pump (Water Overlay)|Pump]]
|Pumps water from the entry with the lowest water level to the entry with the highest water level.
|}

==Polygon skeleton==
A method to obtain a line geometries from a polygonal geometry is called topological skeletonization. The method used by {{software}} is described in: [[Polygon skeleton]].
In the case of Line-based constructions, we want to obtain only a single line segment.
Currently only a simple implementation is used:
#Skeletonize a construction's polygon. This potentially produces a multi-line geometry.
#Take the first point and the last point of this line geometry. These two points will form the line segment used for the line-based construction.

[[File:skeleton_polygon1.png|thumb|left|x150px|Simple rectangle polygon.]]
<br style='clear:left;'>
The method above is simple, but not robust in all cases. See the following images:

<div><ul>
<li style="display: inline-block;">[[File:skeleton_polygon2.png|thumb|x150px|top|left|Case one: Polygon with skeleton that has 3 end points.]]</li>
<li style="display: inline-block;">[[File:skeleton_polygon3.png|thumb|x150px|top|left|Case two: Circle polygon without any end points.]]</li>
<li style="display: inline-block;">[[File:skeleton_polygon4.png|thumb|x150px|top|left|Case three: Almost circular polygon with very small skeleton.]]</li>
</ul></div>
In case one, the resulting skeleton lines have 3 different end points. Which of these points will be the first and last end point is dependent on the sequence of coordinates in the polygon.<br>
In case two, the polygon is a perfect circle, resulting in no skeleton line.<br>
In case three, the skeleton line is very small, for example 1 centimeter. This may not be desirable when the end points need to be separated more than a certain amount.<br>

More complex but common situation:
<div><ul>
<li style="display: inline-block;">[[File:roof_polygon1.png|thumb|150px|top|left|Skeleton of semi-complex construction polygon.]]</li>
<li style="display: inline-block;">[[File:slanted_roof1.png|thumb|150px|top|left|Resulting roof from construction polygon and skeleton.]]</li>
</ul></div>
Generally, this kind of polygon is undesirable for a line-based construction, since it will generate a skeleton with many end points.

==General advice==
*The line-based buildings should be supplied as rectangles or line-buffered polygons.
*The length of the polygon along the line should be longer than the width of the polygon perpendicular to the line.

==See also==
*[[Polygon skeleton]]
*[https://en.wikipedia.org/wiki/Topological_skeleton Topological skeleton]

{{Water Module buttons}}

← Older revision		Revision as of 11:34, 5 October 2022
Line 1:		Line 1:
	Line based [[Building\|buildings]] are ~~constructions~~ for which their geometry is interpreted as a 2 dimensional line with two end points.		Line based [[Building\|buildings]] are Buildings for which their geometry is interpreted as a 2 dimensional line with two end points.

	Examples of line based buildings are the following hydraulic structures:		Examples of line based buildings are the following hydraulic structures:
Line 22:		Line 22:
	==Polygon skeleton==		==Polygon skeleton==
	A method to obtain a line geometries from a polygonal geometry is called topological skeletonization. The method used by {{software}} is described in: [[Polygon skeleton]].		A method to obtain a line geometries from a polygonal geometry is called topological skeletonization. The method used by {{software}} is described in: [[Polygon skeleton]].
	In the case of Line-based ~~constructions~~, we want to obtain only a single line segment.		In the case of Line-based buildings, we want to obtain only a single line segment.
	Currently only a simple implementation is used:		Currently only a simple implementation is used:
	#Skeletonize a ~~construction~~'s polygon. This potentially produces a multi-line geometry.		#Skeletonize a building's polygon. This potentially produces a multi-line geometry.
	#Take the first point and the last point of this line geometry. These two points will form the line segment used for the line-based ~~construction~~.		#Take the first point and the last point of this line geometry. These two points will form the line segment used for the line-based building.

	[[File:skeleton_polygon1.png\|thumb\|left\|x150px\|Simple rectangle polygon.]]		[[File:skeleton_polygon1.png\|thumb\|left\|x150px\|Simple rectangle polygon.]]
Line 42:		Line 42:
	More complex but common situation:		More complex but common situation:
	<div><ul>		<div><ul>
	<li style="display: inline-block;">[[File:roof_polygon1.png\|thumb\|150px\|top\|left\|Skeleton of semi-complex ~~construction~~ polygon.]]</li>		<li style="display: inline-block;">[[File:roof_polygon1.png\|thumb\|150px\|top\|left\|Skeleton of semi-complex building polygon.]]</li>
	<li style="display: inline-block;">[[File:slanted_roof1.png\|thumb\|150px\|top\|left\|Resulting roof from ~~construction~~ polygon and skeleton.]]</li>		<li style="display: inline-block;">[[File:slanted_roof1.png\|thumb\|150px\|top\|left\|Resulting roof from building polygon and skeleton.]]</li>
	</ul></div>		</ul></div>
	Generally, this kind of polygon is undesirable for a line-based ~~construction~~, since it will generate a skeleton with many end points.		Generally, this kind of polygon is undesirable for a line-based building, since it will generate a skeleton with many end points.

	==General advice==		==General advice==