Ensure normals have no zero component.

MOUL/DX9 will not rt light any vertex with a near-zero component in its
normal. This prevents shadows and decals from appearing on flat surfaces
in Ages exported for the MOUL engine. Instead of fighting with the
pipeline and vertex buffer code in Plasma, we'll just clamp the values
here.

korman/exporter/mesh.py

@@ -363,10 +363,13 @@ class MeshConverter(_MeshManager):
 
                     # If this face has smoothing, use the vertex normal
                     # Otherwise, use the face normal
-                    if use_smooth:
-                        geoVertex.normal = hsVector3(*source.normal)
-                    else:
-                        geoVertex.normal = hsVector3(*tessface.normal)
+                    normal = source.normal if use_smooth else tessface.normal
+
+                    # MOUL/DX9 craps its pants if any element of the normal is exactly 0.0
+                    normal = map(lambda x: max(x, 0.01) if x >= 0.0 else min(x, -0.01), normal)
+                    normal = hsVector3(*normal)
+                    normal.normalize()
+                    geoVertex.normal = normal
 
                     geoVertex.color = hsColor32(*vertex_color)
                     uvs = [hsVector3(uv[0], 1.0 - uv[1], 0.0) for uv in uvws]