Polygon vector layers are typically easy to integrate, alongside a mesh. When working with such data, the main choices are ‘2D polygon’ and ‘3D Extrusion’. In addition to these, a third option, ‘Water’, enables animated water effects.
Alongside the ‘Layer style’ panel, the ‘Layer properties’ panel, selectable from the same pop-up list, is also available. This includes parameters for things like ‘transparency’, ‘elevation’ and ‘visibility range’.
Upon adding a polygon layer into a scene, it may initially be visualised using just some simple black outlines. If you’re working with a mesh, this can be a problem, as these lines can become hidden, making it appear that your layer has failed. Fortunately, this issue will resolve itself upon the selection of one of the ‘Layer style’ options. Alternatively, you can temporarily hide the mesh layer, using the eyeball icon, to obtain an unobstructed view.
A simple, unclassified, polygon layer can be effectively used to draw attention to significant areas within a mesh. The ‘2D Polygon’ option, from within the ‘Layer style’ panel, should be sufficient to achieve this. As can be seen in the following figure, adding a degree of transparency to that layer will likely prove effective.
If you’re working with a set of categorised polygons, extending the previous method to make use of the ‘Choose the main attribute to visualise’ option can achieve worthwhile results. Choosing a suitable attribute from this drop-down list will automatically assign categorised colours to each polygon. However, these colour choices, along with other attributes, can be subsequently edited for each individual category from within the Options screen.
Again, in the following example, transparency has been adjusted to ensure that mesh detail is still easily visible.
As with all such vector layers, individual features can be selected by left-clicking on them. Any associated attribution is then displayed within a pop-up menu.
Finally, it should be noted that, upon selecting a categorisation attribute, AGOL removes the option to render the polygons as animated water.
If the ‘3D Extrusion’ option is chosen from the ‘Layer style’ panel, the selected polygon layer will still be draped over your mesh. However, it will also be vertically extruded to form solid objects. Due to the erratic nature of mesh geometries, the result of this can often be unappealing, as is evident in the example below:
It seems probable that the ‘3D Extrusion’ option wasn’t created with mesh-based applications in mind. Instead, this is something that’s going to be more useful when directly working with building footprint data, perhaps in a more standard mapping environment.
The third of the polygon-orientated ‘Layer style’ options is specific to the representation of water extents. When used alongside a mesh, this works in much the same way as the ‘2D Polygon’ option, in so far as it drapes the nominated polygon layer over the mesh surface. However, as the name implies, this option renders the polygons as an animated water surface. In an appropriate environment, this will include reflections of the surrounding scene. It’s a very nice effect.
To set up an effective water scene, you will likely need to adjust settings in both the ‘Layer style’ and ‘Layer properties’ panes. Specifically, if you should notice that the water polygon is not visible and that the layer name is ‘greyed out’, the Visibility Range parameter may need adjusting. Also, if you’re depicting rivers or lakes, it’s also likely that you’ll need to change the water’s colour to something more appropriate than the default bright blue!
