Applies the terrain texturing information, i.e. “colors” the terrain with textures.
Texture Output final result depends on the layer order. Layers are blended together similarly to the layer system in Photoshop and other graphics editors: Each of the upper layers overlaps the lower ones. A mathematical algorithm for each layer generator multiplies all underlying layer values with the inverse value (1-value) of the current layer.
Texture Output layers can have output connections. These connections store a processed and blended layer mask. The sum of the output map values is always equal to 1. These outputs could be used for further map processing (for example, for planting grass using the grass map so it really gets on the terrain).
Each layer could be selected by clicking on it. Above the layers, next to the "Layers:" label you can see layer control buttons:
Add: will add new layer atop of the selected one.
Remove: removes currently selected layer.
Up: will change the layers order by moving the selected layer up.
Down: will change the layers order by moving the selected layer down.
The Background layer does not require an input since it is regarded as completely filled (a constant of 1). This layer could not be removed or sent up or down.
Note that due to better terrain welding splat prototypes the size parameter should be equal to a power of 2.
Recent MapMagic versions were changed in order to work with the new Unity's terrain layer system. You've got to create the terrain layer using the standard ways (check Unity manual) and then assign it to MM's Textures Output node. However, the old way still works with the legacy Splat Output node - at least until Unity will deprecate splatmaps.