Hi Steve,
quote: However, when you IMPORT an NGon with vertex normals, each vertex has it's own normal, and the internal smoothing algorithm is turned off, resulting in artefact free rendering. In Modo this is even more evident. Where vertex normals exist, changing the smoothing angle for a mesh has no effect at all.
Yup, this is absolutely correct - imported vertex normals completely take the place of any kind of "break angle" or "smoothing group" type smoothing mechanisms.
Those other kinds of mechanisms like a break angle method only work by averaging together the normals of all the faces that share a vertex, which can be affected by the polygon topology.
A rendering with imported vertex normals does not have shading affected by topology at all - the imported vertex normals completely define how the polygon is being shaded, neighboring polygons don't have any influence on it.
Additionally with CAD model imports, the vertex normals are very accurate because they come from the original CAD data. Things like a part with a sphere in it will have the exact vertex normal from the original sphere surface, etc... There's no way for something that cooks up normals just by averaging already faceted data to come up with the precise original normals like that.
- Michael |
