engine.py

if mesh.materials:
        _Name = _CleanNames("M", itertools.count())
        if mesh.materials[0].use_nodes:
            for _node in mesh.materials[0].node_tree.nodes:
                if isinstance(_node, nt.ArnoldNodeOutput) and _node.is_active:
                    for input in _node.inputs:
                        if input.is_linked:
                            # Displacement Mapping (Arnold needs map to be a pointer to the array of nodes pointing to displacement)
                            if input.identifier == "disp_map":
                                dispnodes = []
                                # _AiNode() converts blender node to arnold node
                                dispnodes.append(_AiNode(input.links[0].from_node, _Name(mesh.materials[0].name), {}))
                                nmaps = len(dispnodes)
                                # Calculate the number of nodes linked to displacement and initialize a numpy array
                                a = numpy.ndarray(nmaps, dtype=numpy.uint8)
                                mm = collections.OrderedDict()
                                # Set up the arnold parameters as NODE INDEX 
                                for i in numpy.unique(a):
                                    mn = _AiNode(input.links[0].from_node, _Name(mesh.materials[0].name), {})
                                    mi = mm.setdefault(id(mn), (mn, []))[1]
                                    mi.append(i)
                                for i, (mn, mi) in enumerate(mm.values()):
                                    a[numpy.in1d(a, numpy.setdiff1d(mi, i))] = i
                                if mm:
                                    nmm = len(mm)
                                    t = mm.popitem(False)
                                    if t:
                                        # Point to the array of nodes
                                        AiDisplace = arnold.AiArrayAllocate(nmm, 1, arnold.AI_TYPE_POINTER)
                                        arnold.AiArraySetPtr(AiDisplace, 0, t[1][0])
                                        i = 1
                                        while mm:
                                            arnold.AiArraySetPtr(AiDisplace, 0, mm.popitem(False)[1][0])
                                            i += 1
                                        # Link Displacement Map to corresponding image node
                                        arnold.AiNodeSetArray(node, "disp_map", AiDisplace)