Example: Create an Area with a Hole

Creating areas is easy, as shown in the Editing Drawings topic , but creating areas that include one or more holes involves a slight nuance.   In this example we will create an area with one hole in it.

 

eg_newobj03_01.png

 

We begin by creating a new drawing.  We open the drawing and click the Create Area tool.

 

eg_newobj03_02.png

 

In the drawing we begin clicking to create coordinates that define the boundary of our area using straight line segments.  The Coordinates tab of the Record panel automatically opens to report coordinates as we click on them.  

 

eg_newobj03_03.png

We click at each location we want to mark a coordinate.

 

eg_newobj03_04.png

 

With each click the proposed area boundary grows.

 

eg_newobj03_05.png

 

At the last coordinate for the area boundary we Shift-Click to mark the coordinate, to indicate that terminates a branch in the area structure, and to indicate we intend to continue creating the area.  

 

eg_newobj03_06.png

 

We then click again to indicate the coordinate that will begin the boundary of the "hole" inside the area. The preceding last coordinate in the branch is marked with an inverted T symbol, indicating the end of a branch.

 

eg_newobj03_07.png

 

As before, each time we click to create a coordinate the boundary of the proposed "hole" is expanded one more segment.

 

eg_newobj03_08.png

 

At the last coordinate we click to mark the coordinate.

 

eg_newobj03_09.png

 

We then right-click the mouse anywhere, to call up the context menu for creating the area.  

 

eg_newobj03_09a.png

In the context menu we choose Save Changes.  We could also have pressed Ctrl-Enter as a keyboard shortcut.

 

eg_newobj03_10.png

 

The result is an area object that has a "hole" in it.  We can Alt-click the area to show its attribute values in the Record panel.

 

eg_newobj03_11.png

 

Clicking on the Coordinates tab of the Record panel we can see the area is created from two branches, the ends of each branch being marked by an inverted T symbol.   One branch is the outer area boundary while the other branch is the inner boundary that defines the hole in the area.

 

This example continues into the related example topic, Example: Create an Area with Holes and Islands.

 

Notes

More holes, please - If we wanted to create more than one hole within the area we could have Shift-clicked the last coordinate of the hole boundary and then clicked into the drawing again to start the next boundary for a hole.

 

See Also

Drawings

 

Coordinates

 

New Object Dialog

 

Example: Draw Lines, Areas and Points - Simple example of using basic mouse moves to add points, lines and areas to a drawing.

 

Example: Trace an Area in a Map over an Image Background - In a map with a drawing layer above an image layer, create an area object in the drawing by tracing over the outlines of something seen in the image layer below.

 

Example: Create a Line using the Record Panel - Step by step creation and modification of a line in a drawing using the Contents - Record panel's Coordinates tab.

 

Example: Create a Line using Curved Segments - Creating a line made up from curvilinear geometry using the New Object Dialog.

 

Example: Create an Area with Holes and Islands - Using the New Object Dialog, create an area in a drawing where the area includes holes and also islands.

 

Example: Create a Multipoint - How to create multipoints using the New Object Dialog.  This topic provides two examples:  First we create a multipoint and then next we create a multipoint having two branches.  The purpose of this topic is to help teach the implementation of geometry in Manifold and other typical spatial packages using a somewhat unusual and rarely met object type, the multipoint, which combines what appear to be many separate points into a single multipoint object.