"- you calculate the vertex normals by the adjacent edge-normals?"
No ... just from the directed edges themselves. They ARE the normals.
I saw some things that alluded to possibility that faces should be triangulated before calculations of vertex normal. But that seems wrong also.
Use the FACE normals ONLY IF the vertex is "isolated" with only two edges. Use all edges as normals (NOT EDGE NORMALS) if the vertex is not isolated. The result is nice.
No ... just from the directed edges themselves. They ARE the normals.
I saw some things that alluded to possibility that faces should be triangulated before calculations of vertex normal. But that seems wrong also.
Use the FACE normals ONLY IF the vertex is "isolated" with only two edges. Use all edges as normals (NOT EDGE NORMALS) if the vertex is not isolated. The result is nice.