This command sets the light sampling type of the current material. Valid light sampling types are either "facet" or "vertex".
Facet-based light sampling (the default) means that each polygon is lit individually by the light source(s) in the world, with a "hard edge" visible from one polygon to the next if the polygons face in different directions. Use facet-based lighting when you want boundaries between the individual polygons making up the object to be visible, for example if you are making an object with lots of right angles, such as a cube.
Vertex-based light sampling causes polygons to be lit continuously from one polygon to the next, so that the surface appears "smooth" and the boundaries between polygons are not visible. Use vertex-based lighting when you are using polygons to approximate a smooth surface, such as a human face.
It should be noted that facet-based light sampling is less efficient that vertex-based light sampling and can lead to substantially lower frame rates on complex objects. The reason for this is that facet-based lighting requires each polygon to have its own private set of vertices whereas vertex-based lighting allows polygons to share vertices.
<sampling> the light sampling type