Select random by loose parts

Question

I have the following mesh. It is a series of hexagons placed on a plane.

I'm trying to select random hexagons to give them another material. I know there is a select random function, but that only works on vertex, edges and faces. I'm trying to do it by loose parts.

Is there an option to do this?

Answer 1

Bmesh Script

Using the script from here (which happened to come up today re another q) that finds all loose parts in a mesh.

Test script, run in edit mode on a mesh. Selects a random loose part on each run.

import bpy
import bmesh
from random import randint

def walk_island(vert):
    ''' walk all un-tagged linked verts '''    
    vert.tag = True
    yield(vert)
    linked_verts = [e.other_vert(vert) for e in vert.link_edges
            if not e.other_vert(vert).tag]

    for v in linked_verts:
        if v.tag:
            continue
        yield from walk_island(v)

def get_islands(bm, verts=[]):
    def tag(verts, switch):
        for v in verts:
            v.tag = switch
    tag(bm.verts, True)
    tag(verts, False)
    ret = {"islands" : []}
    verts = set(verts)
    while verts:
        v = verts.pop()
        verts.add(v)
        island = set(walk_island(v))
        ret["islands"].append(list(island))
        tag(island, False) # remove tag = True
        verts -= island
    return ret

#test code
context = bpy.context
ob = context.edit_object
me = ob.data
bm = bmesh.from_edit_mesh(me)

islands = [island for island in get_islands(bm, verts=bm.verts)["islands"]]
if len(islands):
    #deselect all
    for v in bm.verts:
        v.select = False
    bm.select_flush(False) 
    for v in islands[randint(0, len(islands) - 1)]:
        v.select = True
    bm.select_flush(True)        
bmesh.update_edit_mesh(me)

Possibly more useful, re a scripting solution, would be to randomly assign materials from a list to loose parts.

Here the single mesh array of suzannes has 6 materials, which are assigned to each loose part randomly.

#test code
context = bpy.context
ob = context.object
me = ob.data
bm = bmesh.new()
bm.from_mesh(me)

islands = [island for island in get_islands(bm, verts=bm.verts)["islands"]]
for island in islands:
    #deselect all
    for v in bm.verts:
        v.select = False
    bm.select_flush(False) 
    for v in island:
        v.select = True
    bm.select_flush(True) 
    mat_index = randint(0, len(me.materials) - 1) 
    for f in bm.faces:
        if f.select:
            f.material_index = mat_index      
bm.to_mesh(me)
me.update()

Answer 2

To select hexagons randomly as in your case, you must use the random function with vertex, edges or faces.

Then simply press " CTRL and L " as mentioned Duarte.

Or press several times " CTRL and Numpad + " to add all part of the hexagons.