Add new addon to gather some custom normals basic editing tools, for until we...

Add new addon to gather some custom normals basic editing tools, for until we add real support for that in BMesh.

For now, only contains an op to flip custom normals (together with other normals).

Related to T46115.

mesh_custom_normals_tools.py

+# ***** BEGIN GPL LICENSE BLOCK *****
+#
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ***** END GPL LICENCE BLOCK *****
+
+bl_info = {
+    "name": "Custom Normals Tools",
+    "author": "Bastien Montagne (mont29)",
+    "version": (0, 0, 1),
+    "blender": (2, 75, 0),
+    "location": "3DView > Tools",
+    "description": "Various tools/helpers for custom normals",
+    "warning": "",
+    "support": 'OFFICIAL',
+    "category": "Mesh",
+}
+
+
+import bpy
+
+
+class MESH_OT_flip_custom_normals(bpy.types.Operator):
+    """Flip active mesh's normals, including custom ones (only in Object mode)"""
+    bl_idname = "mesh.flip_custom_normals"
+    bl_label = "Flip Custom Normals"
+    bl_options = {'UNDO'}
+
+    @classmethod
+    def poll(cls, context):
+        return context.object and context.object.type == 'MESH' and context.object.mode == 'OBJECT'
+
+    def execute(self, context):
+        me = context.object.data
+
+        if me.has_custom_normals:
+            me.calc_normals_split()
+            clnors = [0.0] * 3 * len(me.loops)
+            me.loops.foreach_get("normal", clnors)
+
+        bpy.ops.object.mode_set(mode='EDIT')
+        bpy.ops.mesh.select_all(action='SELECT')
+        bpy.ops.mesh.flip_normals()
+        bpy.ops.object.mode_set(mode='OBJECT')
+
+        me = context.object.data
+        if me.has_custom_normals:
+            clnors[:] = list(zip(*[(-n for n in clnors)] * 3))
+            # We also have to take in account that the winding was reverted...
+            for p in me.polygons:
+                ls = p.loop_start + 1
+                le = ls + p.loop_total - 1
+                clnors[ls:le] = reversed(clnors[ls:le])
+            me.normals_split_custom_set(clnors)
+
+        context.scene.update()
+        return {'FINISHED'}
+
+
+def flip_custom_normals_draw_func(self, context):
+    if isinstance(self, bpy.types.Panel):
+        self.layout.label("Custom Normal Tools:")
+    self.layout.operator(MESH_OT_flip_custom_normals.bl_idname)
+
+
+def register():
+    bpy.utils.register_module(__name__)
+    bpy.types.VIEW3D_PT_tools_object.append(flip_custom_normals_draw_func)
+
+
+def unregister():
+    bpy.types.VIEW3D_PT_tools_object.remove(flip_custom_normals_draw_func)
+    bpy.utils.unregister_module(__name__)
+
+
+if __name__ == "__main__":
+    register()