Add weights from influence based on distance

influence_from_distance.py

import maya.cmds as mc
import math

        
def mesh_verts_distance_from_point(point, transform_with_shape):
    distance_between = lambda p1, p2: math.sqrt(sum([(a - b) ** 2 for a, b in zip(p1, p2)]))    
    shapes = mc.listRelatives(transform_with_shape, s=True, c=True, type='mesh')
    distances = {}
    if shapes:
        mesh_verts = mc.ls("{MESH}.vtx[*]".format(MESH=shapes[0]), fl=True)
        return {vert:distance_between(mc.xform(vert, ws=True, t=True, q=True), point) for vert in mesh_verts}
    return distances
    

def normalize_vert_distance_dict(vert_dist_dict, tolerance=4.1):
    for vert in vert_dist_dict.keys():
        distance = vert_dist_dict[vert]
        if distance <= tolerance :
            vert_dist_dict[vert] = 1 - (distance /tolerance)
        else:
            vert_dist_dict.pop(vert)
    return vert_dist_dict

def set_influence_based_on_distance(transform_with_mesh, influences, tolerance=3, additive=False):
    skin_clusters = mc.ls(mc.listHistory(transform_with_mesh), type='skinCluster')
    if skin_clusters:
        skin_cluster = skin_clusters[0]
        for influence in influences:
            vert_distance_table = normalize_vert_distance_dict(mesh_verts_distance_from_point(mc.xform(influence, ws=True, t=True, q=True), transform_with_mesh), tolerance=tolerance)
            for vert in vert_distance_table:
                value = vert_distance_table[vert]
                if additive:
                  value += mc.skinPercent(skin_cluster, vert, transform=influence, q=True)
                mc.skinPercent(skin_cluster, vert, tv=(influence, value), normalize=True )

# Select a mesh that has a skinCluster and then any joints/influences that are already a part of the cluster influences.
# Play with the tolerance value to change the distance of mesh affected.
# Use the additive flag to add onto preexisting weights that were already assigned.
set_influence_based_on_distance(mc.ls(sl=True)[0], mc.ls(sl=True)[1:], tolerance=3, additive=True)