import bpy
import bmesh
from mathutils import *

#
# take a mesh and alter it so that it has subdivided spikes.
# Each layer of spikes gets its own bone.
#

def average( coords):
    sum = Vector(coords[0])
    for i in range(1, len(coords)):
        sum = sum + coords[i]
    return sum / len(coords)

def fab_layer(verts, base_indices, layer, max_layers, max_radius):

    vavg = average( [ verts[vi] for vi in base_indices])

    tip = vavg * max_radius / vavg.magnitude

    rval_vi = []

    for i in range(len(base_indices)):
        v0 = verts[base_indices[i]]
        v1 = (v0 * (max_layers-layer) + tip*layer ) / max_layers
        idx = len(verts)
        rval_vi.append(idx)
        verts.append(v1)

    return rval_vi

def bridge_rings(faces, ring1, ring2):

    n = len(ring1)
    for i in range(n):
        v1 = ring1[i]
        v2 = ring1[ (i+1)%n]
        v3 = ring2[ (i+1)%n]
        v4 = ring2[i]
        faces.append( [ v1,v2,v3,v4] )

def spikify(proto, layers=5, max_radius=3):

    mesh = bpy.data.meshes.new("spikes")

    verts = [ v.co for v in proto.vertices ]
    faces = []

    vi_for_layer = [ [] for r in range(layers)]

    for poly in proto.polygons:
        if poly.select:
            # spikify this one
            old_ring = poly.vertices
            for r in range(layers):
                new_ring = fab_layer(verts, poly.vertices, r+1, layers, max_radius)

                vi_for_layer[r].extend(new_ring)
                bridge_rings(faces, old_ring, new_ring)

                old_ring = new_ring
            faces.append( old_ring)

    bpy.ops.object.mode_set(mode='OBJECT')
    mesh.from_pydata(verts, [], faces)

    for p in mesh.polygons:
        p.use_smooth=True

    obj = bpy.data.objects.new("spikes", mesh)

    #

    for layer in range(layers+1):
        vg = obj.vertex_groups.new("layer %d"%layer)
        if (layer==0):
            vg.add(range(len(proto.vertices)), 1, 'REPLACE')
        else:
            vg.add(vi_for_layer[layer-1], 1, 'REPLACE')

    #

    arm = bpy.data.armatures.new("spikes")
    ao = bpy.data.objects.new("armature.%s"%"spikes", arm)
    scn.objects.link(ao)

    scn.objects.active = ao
    bpy.ops.object.mode_set(mode='EDIT')

    for layer in range(layers+1):
        b = arm.edit_bones.new("layer %d"%layer)
        b.head = (0,0,0)
        if (layer >0) :
            z = max_radius * layer / layers
        else:
            z = -1
        # if we don't set the tail!=head, the bone disappears
        b.tail = (0,0, z)

    bpy.ops.object.mode_set(mode='OBJECT')

    #

    mod = obj.modifiers.new("armature", "ARMATURE")
    mod.object = ao

    #

    return obj


#if bpy.context.mode != 'EDIT':
#    bpy.ops.object.mode_set(mode='EDIT')

scn = bpy.context.scene
obj = spikify(bpy.context.active_object.data, 40, 10)
scn.objects.link(obj)