Merge pull request #357 from AlpenAalAlex/issue349-Exporting-URDF-wit…

…h-0-mass-causes-divide-by-zero-error

Fix merging inertials with mass 0

phobos/blender/model/inertia.py

@@ -201,7 +201,35 @@ def combine_com_3x3(objects):
  for obj in objects:
  combined_com = combined_com + obj.matrix_local.translation * obj['mass']
  combined_mass += obj['mass']
- combined_com = combined_com / combined_mass
+ if combined_mass != 0:
+ combined_com = combined_com / combined_mass
+ else:
+ combined_com = mathutils.Vector((0.0,) * 3)
+ combined_volume = 0
+ for obj in objects:
+ # calculate volume
+ mesh = representation.Mesh(
+ mesh=obj.data.copy(),
+ meshname=obj.data.name
+ )
+ volume, _ = mesh.approx_volume_and_com()
+ center = obj.matrix_local.translation
+
+ combined_volume += volume
+ combined_com = combined_com + center * volume
+ combined_com = combined_com / combined_volume
+
+ if len(objects) > 1:
+ all_objects = ""
+ for i in range(len(objects)):
+ obj = objects[i]
+ if i == 0:
+ all_objects += obj.name
+ elif i == len(objects)-1:
+ all_objects += " and "+obj.name
+ else:
+ all_objects += ", "+obj.name
+ log(message=f"Mass of {all_objects} totals 0. Weighing by volume", level='INFO')
  log(" Combined center of mass: " + str(combined_com), 'DEBUG')
  return combined_mass, combined_com