Hi Phil, also if it helps any here is again the quote from the OBJ format spec:
quote:
vn i j k
Polygonal and free-form geometry statement.
Specifies a normal vector with components i, j, and k.
Vertex normals affect the smooth-shading and rendering of geometry.
For polygons, vertex normals are used in place of the actual facet
normals. For surfaces, vertex normals are interpolated over the
entire surface and replace the actual analytic surface normal.
When vertex normals are present, they supersede smoothing groups.
i j k are the i, j, and k coordinates for the vertex normal. They
are floating point numbers.
Note the part that I put in bold - it is intended that when vertex normals are present in an OBJ file, that they are used to shade the polygons and smoothing groups actually have no role in the rendering.
Smoothing groups is a mechanism that you use when you are trying to create vertex normals from a bunch of polygons - if you have some better quality normals like ones that came from a NURBS surface, you need to use those better quality ones instead of trying to create new ones which will not be as accurate.
- Michael |
