It's meant to be simple and easy to use, and therefore it has been made as a custom editor of MeshFilter. It needs no preparations.
Drop the file in an Editor folder.
- store the normals length i editor prefs
- adjust the normals length in the mesh filter inspector
You've probably noticed this script creates massive slowdown on complex objects. This is for two reasons:
All you need to do is move the handles.matrix and colour lines outside the loop, and cache mesh.vertices and mesh.normals in local arrays, too:
Vector3 verts = mesh.vertices;
Vector3 norms = mesh.normals;
for (int.....)
{
Handles.DrawLine(verts[i],verts[i]+norms[i])
}