Subdivide.py

# This Python script for Blender first tries to convert all the Blender scene meshes into quads
# It will then proceed to merge all vertices that occupy the same position
# Lastly, it will subdivide the quad edges until every edge has at least the length of the "max_edge_length" variable
# You can use this script to subdivide the scene into quads, which is ideal for vertex lighting
# Please set the "max_edge_length" and "vert_merge_distance" variables value accordingly

# Set the maximum edge length here. The smaller the value, the more the edges get subdivided
max_edge_length = 300.0

# Set the minimum distance a vertex can have from each other not to be merged here
vert_merge_distance = 0.00001

import bpy
import bmesh

def remove_duplicates(obj, merge_distance):
    bpy.context.view_layer.objects.active = obj
    bpy.ops.object.mode_set(mode='EDIT')
    
    bpy.ops.mesh.select_all(action='SELECT')
    
    bpy.ops.mesh.remove_doubles(threshold = merge_distance)
        
    bpy.ops.object.mode_set(mode='OBJECT')

def tris_to_quads(obj):
    bpy.context.view_layer.objects.active = obj
    bpy.ops.object.mode_set(mode='EDIT')
    
    bpy.ops.mesh.select_all(action='SELECT')
    
    bpy.ops.mesh.tris_convert_to_quads()
    
    bpy.ops.object.mode_set(mode='OBJECT')

def subdivide_quads_by_length(obj, max_length):
    bpy.context.view_layer.objects.active = obj
    bpy.ops.object.mode_set(mode='EDIT')
    
    me = obj.data
    bm = bmesh.from_edit_mesh(me)
    
    subdivided_edges = set()
        
    for face in bm.faces:
        for edge in face.edges:
            if edge.calc_length() > max_length:
                if edge not in subdivided_edges:
                    subdivided_edges.add(edge)
    
    bmesh.ops.subdivide_edges(bm, edges=list(subdivided_edges), cuts=1, use_grid_fill=True, use_only_quads=True)
    
    bmesh.update_edit_mesh(me)
    bpy.ops.object.mode_set(mode='OBJECT')

    return bool(subdivided_edges)

for obj in bpy.context.scene.objects:
    if obj.type == 'MESH':
        tris_to_quads(obj)
        
        remove_duplicates(obj, vert_merge_distance)
        
        subdivide = True

        while subdivide:       
                subdivide = subdivide_quads_by_length(obj, max_edge_length)