• InfoWorks ICM

Adding voids to exclude areas from the 2D mesh

Add polygons as voids that can be used for excluding areas from the 2D mesh, such as buildings.

Step-by-step guide

Voids are polygon mesh objects that can be used for excluding areas from the 2D mesh. A common use of voids is to represent buildings within the 2D area.

The advantage of using voids is that they reduce the overall number of mesh elements and therefore simulation time. The disadvantage is that they represent an infinitely high impermeable barrier, which is unrealistic.

To add voids to a 2D mesh, polygons are created and associated with a common category name. In this example model, there are several polygons already created to represent buildings.

In an example model, polygons representing buildings appear as brown rectangles on a green background.

To associate a common category, so that the mesh engine knows which polygons to use:

  1. From the Windows toolbar, Grid windows drop-down, select New polygons window.

In the Windows toolbar, the Grid windows drop-down expanded, with New polygons window selected and highlighted in red.

  1. In the grid window, switch to the Polygon tab.
  2. Click the Category column header to select the column.
  3. Right-click the column and select Current cell(s) Value > Set new value(s) for cell(s).

The grid window, Polygon tab, with the Category column header selected; and in the context menu, Current cell(s) Value Set selected, with Set new value(s) for cell(s) selected in the flyout.

  1. In the New Cell Value popup, enter a value of “Voids”.
  2. Click OK.

In the grid window, Polygon tab, the selected Category column now has a value of Voids in each row.

  1. Close the window.

Now, re-mesh the 2D zone to include these changes in the mesh:

  1. On the GeoPlan, select the 2D zone.
  2. From the Model menu, select Meshing > Mesh 2D zones.

In the Model menu, Meshing selected, and in the flyout, Mesh 2D zones selected and highlighted in red.

  1. In the Mesh 2D Zones dialog box, under Voids, select Polygons.
  2. From the drop-down, select the Voids category.

In the Mesh 2D Zones dialog box, under Voids, Polygons enabled and Voids selected in the drop-down.

  1. From the Database, drag the Ground model into the Mesh 2D Zones dialog box, and drop it into the Ground Model box.
  2. Click OK to mesh the 2D zone.
  3. In the Schedule Job(s) popup, click OK.
  4. In the Job Control window, under Status, click Mesh ready.
  5. In the Manage mesh results dialog box, click Load mesh.
  6. Click Close.

When the mesh loads, the polygon areas are excluded from the mesh generation, as they have no internal 2D elements. Therefore, the boundaries are treated as an infinitely high impermeable barrier by the 2D engine.

To view these excluded areas within the mesh, turn off the display of polygons:

  1. In the GeoPlan, right-click and select Properties & Themes.
  2. On the Layers and Themes tab, for the Polygons layer, deselect Display.
  3. Click OK.

In the GeoPlan, the 2D mesh appears around brown rectangular polygon voids representing buildings; and in the GeoPlan Properties and Themes dialog box, Display is disabled for the Polygon row, with OK selected.

Now, the areas excluded by the polygon voids are visible within the 2D mesh.

With the polygon voids hidden, the model shows rectangular areas of the same color, but with no triangles, excluded from the 2D mesh.