Updated GeometricPrimitive (markdown)

GeometricPrimitive.md

@@ -355,6 +355,6 @@ GeometricPrimitive makes use of the following states:
 The GeometricPrimitive class assumes you've already set the Render Target view, Depth Stencil view, and Viewport.
 
 # Remark
-Tetrahedron, Cube/Hexahedron, Octahedron, Dodecahedron, and Icosahedron comprise the five [Platonic solids](https://en.wikipedia.org/wiki/Platonic_solid).
+Tetrahedron, Cube/Hexahedron, Octahedron, Dodecahedron, and Icosahedron comprise the five [Platonic solids](https://en.wikipedia.org/wiki/Platonic_solid). The surface normals for these shapes are constructed as "face-normals" for faceted shading.
 
 The *Utah Teapot* (also known as the *Newell Teapot*) is sometimes jokingly referred to as the "Sixth Platonic solid" due to its prevalence in rendering sample images. It was created in 1975 by Martin Newell at the University of Utah. It's become the "Hello, world" of 3D models hence why it's included as a basic geometric primitive shape in *DirectX Tool Kit*.