The question isn't new but I've not succeeded to find an appropriate answer. I need to differ faces_shade_smooth when it's applied only to a faces group but groups aren't smoothed between them. I've succeded to find only use_smooth property and the built-in export script acts the same way (i. e. doesn't differ smooth groups).

I've found how to do it from UI but I don't know how can I export it in a script.

Tell me please how can I exactly get if a particular polygon that uses smooth does belong to some group or doesn't (i. e. if it should be smoothed with some other polygon or not).

by groups you mean vertex groups right?

hope this helps:

Code:

import bpy o = bpy.context.object m = o.data print("Object:   %s" % o.name) print("Mesh:     %s" % m.name) print("Polygons: %i" % len(m.polygons)) print() for poly in m.polygons:         if not poly.select:         continue         print("Polygon %i smooth? %s" % (poly.index, poly.use_smooth))     for vert_index in poly.vertices:         vertex = m.vertices[vert_index]                 print("  Vertex %i" % vert_index)         print("  Vertex groups: %i" % len(vertex.groups))         for g in vertex.groups:             print("    %s" % o.vertex_groups[g.group].name)         print()

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Unfortunantly that is not I'm looking for. I've already tried this way and found out that smooth groups don't match vertex groups (really I'm not sure if smooth groups are represented for vertices, edges or polygons). E. g. if I select a mesh, enter in edit mode, select some polygons, press W and select from popup menu "Shade smooth" I don't create a vertex group. I can see that in the object data tab the list of vertex groups is still empty.

The smooth groups effect is only that polygons are being smoothed only inside groups but not between them. Such feature was for a long time 3D Studio Max and appeared only in some latest versions of Blender. The problem is how to export it, standard scripts still are not modified for this new feature.

the operator exec function of bpy.ops.mesh.faces_shade_smooth call:

mesh_set_smooth_faces(em, 1);

which does:

Code:

BMIter iter;    BMFace *efa;    if (em == NULL) return;        BM_ITER_MESH (efa, &iter, em->bm, BM_FACES_OF_MESH) {       if (BM_elem_flag_test(efa, BM_ELEM_SELECT)) {          BM_elem_flag_set(efa, BM_ELEM_SMOOTH, smooth);       }    }

in python it would be:

Code:

for efa in bm:     if efa.select:         efa.use_smooth = smooth # 0 or 1

so my above code is right, the information is stored in poly.use_smooth
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I'm sitting, waiting, wishing, building Blender in superstition...