Marat Yakupov reported in issue 228 a problem with the mixamo ybot model. The problem is caused by the multiple sections available in the mesh. The mixamo.py has been updated to support multiple sections:

def fix_bones_influences(self, mesh, old_skeleton):

active_bones = []

for section in range(0, mesh.skeletal_mesh_sections_num()):

vertices = mesh.skeletal_mesh_get_soft_vertices(0, section)

ue.log_warning(len(vertices))

new_vertices = []

old_bone_map = mesh.skeletal_mesh_get_bone_map(0, section)

new_bone_map = []

for vertex in vertices:

bone_ids = list(vertex.influence_bones)

for index, bone_id in enumerate(bone_ids):

if vertex.influence_weights[index] > 0:

bone_ids[index] = self.get_updated_bone_index(old_skeleton, mesh.Skeleton, old_bone_map, new_bone_map, bone_id)

if new_bone_map[bone_ids[index]] not in active_bones:

active_bones.append(new_bone_map[bone_ids[index]])

vertex.influence_bones = bone_ids

new_vertices.append(vertex)

# assign new vertices

mesh.skeletal_mesh_set_soft_vertices(new_vertices, 0, section)

# add the new bone mapping

mesh.skeletal_mesh_set_bone_map(new_bone_map, 0, section)

# specify which bones are active and required (ensure root is added to required bones)

mesh.skeletal_mesh_set_active_bone_indices(active_bones)

# mark all the bones as required (eventually you can be more selective)

mesh.skeletal_mesh_set_required_bones(list(range(0, mesh.Skeleton.skeleton_bones_get_num())))

As you can see we still assume a single LOD (the 0 before the section is always the lod)