Since QGis version 2.10 you have at your disposal a powerful tool to format the vector layers symbols.
The layer effects provide the ability to add different effects in the rendering chain of a symbol. With these effects , you can place a shadow range under the symbol, modifying and highlighting the rendering symbol. You can also use these effects overlapped and indicate if the effect will be gradual, ie if it applies in the rendering state (it modifies the rendering already modified by others effects ) or discreet , by re-entering the geometric source in the rendering chain ( modifying the original symbol without taking into account other effects and by adding them to these ).
Let’s discuss a few examples that will clarify all the previous. Firstly , where is this option located? Open Layer Properties-> Style
Check the Effects box to activate the effects on this layer and click the Effects button to open the Effect Settings window.
Out of the 5 available effects types, you have by default the effect Source. In fact it is a non- effect because this option displays the original symbol of the layer . On the other side, if you apply , for example , a given shadow and you uncheck Source , on your map, you will see only the shadows of the entities of this layer but not the entities themselves .
The effects are drawn the following order of this window , the one placed the lowest is drawn first whereas the one placed the highest, the last . The arrows allow moving an effect up or down.
With the + button , you can add other effects to the 5 by default effects.
Let’s discuss how these effects are translated in a data layer. We will use a cadastre layer as example .
Let’s apply a given shadow to the buildings:
You will observe that the right panel allows setting up all the parameters of the selected effect. The effect is conveyed as follows:
To increase the separation effect between the buildings and the plots, we will add an external luminescence zone .
This effect will be applied after the shadow generation :
You can control the way the effects are applied in the effects chain, with the option Drawing Mode
The rendering mode only applies the effect to the original symbol, not to the rendering status when applying the effect . In our case the external Luminescence will be applied, just, to the original polygon and not to the selected shadow .
The Edit option does not have any effect at the top of the pile since it modifies the rendering without displaying it . It is used to change the status of the rendering that will be passed to the effects being above it in the effects stack.
The default mode, Rendering and Edit is the combination of both: it applies the effect, draws and passes to the effects located above the stack.
We cannot see here all the possible effects combinations and their renderings, but try , you will be surprised with all you can do to make more striking the renderings of your maps.
