Weight paint maps in/out of Blender to allow editing in Photoshop or other

Question

I have seen this thread: How can I use an image texture as a guide for weight painting?

and it allows me to use textures as a guide for weight painting... but is it possible to get weight paint maps in and out of Blender, so they could be edited with a more sophisticated image editor?

Answer 1

This script will convert weight to vertex color and vertex color to weight :

• the script create new groups if they don't exist and overwrite old groups with the same names
• the script use two methods for conversions grayscale<-->weight and RGB<-->weight
• the conversion works in two ways weight--> color and color-->weight

HOW TO USE:

• run the script once "it will be registered"
• in 3D view select the object
• hit space and type weight&color
• choose the settings and conversion hit OK
• new groups or vertex color maps will be created with the appropriate values "the viewport will change to show the result"

---

import bpy
from bpy.types import Operator
from bpy.props import EnumProperty
from mathutils import Color

bl_info = { 
    'name': 'Convert Vertex Color to Weights',
    'author': 'Chebhou on StackExchange, refactor by aliasguru',
    'version': (0, 1, 0),
    'blender': (2, 7, 5),
    'location': '3D View > Spacebar Menu > weight & color',
    'description': 'converts Vertex colors to weights and vice versa',
    'tracker_url': '',
    'wiki_url': 'http://blender.stackexchange.com/questions/26467/weight-paint-maps-in-out-of-blender-to-allow-editing-in-photoshop-or-other',
    'support': 'COMMUNITY',
    'category': '3D View'}



color = 'HSV' #'HSV'    method used for conversion


def convert(value, method):
    if method == 'BW2W':
        return  (value.r + value.g+ value.b)/3
    elif method == 'W2BW':
        col = Color((value, value, value))
        return col
    elif method == 'HSV2W':
        return  1-(value.h / 0.66)
    elif method == 'W2HSV':
        col = Color()
        col.hsv = (0.66*(1-value), 1, 1)
        return  col


def vert_col2weight(context, color):    
    color_maps = context.object.data.vertex_colors
    for color_map in color_maps :
        group_name = color_map.name

        #check for existing group with the same name
        if None == context.object.vertex_groups.get(group_name): 
            context.object.vertex_groups.new( name = group_name)  

        group_ind = context.object.vertex_groups[group_name].index

        for poly in context.object.data.polygons:
                    for loop_ind in poly.loop_indices:
                        vert_ind =context.object.data.loops[loop_ind].vertex_index  
                        col = color_map.data[loop_ind].color
                        if color == 'BW':
                            weight = convert(col, 'BW2W')
                        else :
                            weight = convert(col, 'HSV2W')
                        context.object.vertex_groups[group_ind].add([vert_ind], weight,'REPLACE')


def weight2vert_col(context, color):               
    vert_groups = context.object.vertex_groups
    col = Color()
    for vert_g in vert_groups:
        group_name = vert_g.name  

        #check for existing group with the same name
        if None == context.object.data.vertex_colors.get(group_name): 
            context.object.data.vertex_colors.new(name=group_name)

        color_map =  context.object.data.vertex_colors[group_name]

        for poly in context.object.data.polygons:
                    for loop_ind in poly.loop_indices:
                        vert_ind =context.object.data.loops[loop_ind].vertex_index 

                        #check if the vertex belong to the group
                        weight = 0
                        for g in context.object.data.vertices[vert_ind].groups:
                            if g.group == vert_groups[group_name].index:
                                weight = vert_groups[group_name].weight(vert_ind) 

                        #convert weight to vert_col          
                        if color == 'BW':
                            col = convert(weight, 'W2BW')
                        else :
                            col = convert(weight, 'W2HSV')
                        #assign to the color map
                        color_map.data[loop_ind].color = col


class   weight_color(Operator):  

    """weight from&to vert_color"""        
    bl_idname = "object.weight_color"  
    bl_label = "weight & color"     
    bl_options = {'REGISTER', 'UNDO'}    #should remove undo ? 

    #parameters and variables
    convert = EnumProperty(
                name="Convert",
                description="Choose conversion",
                items=(('W2C', "Weight to vertex color", "convert weight to vertex color"),
                       ('C2W', "Vertex color to weight", "convert vertex color to weight")),
                default='W2C',
                )
    color = EnumProperty(
                name="Color type",
                description="Choose a color system",
                items=(('BW', "Gray scale", "map weight to grayscale"),
                       ('HSV', "RGB color", "map weight to rgb colors")),
                default='HSV',
                )
    #main function
    def execute(self, context): 
        bpy.ops.object.mode_set(mode = 'OBJECT')
        if self.convert == 'W2C':
            weight2vert_col(context, self.color)
            bpy.ops.object.mode_set(mode = 'VERTEX_PAINT')
        else:
            vert_col2weight(context, self.color)
            bpy.ops.object.mode_set(mode = 'WEIGHT_PAINT')

        context.active_object.data.update()
        self.report({'INFO'},"Conversion is Done")
        return {'FINISHED'}
    #get inputs 
    def invoke(self, context, event):
            wm = context.window_manager
            return wm.invoke_props_dialog(self)


def addObject(self, context): 
    self.layout.operator(
    weight_color.bl_idname,
    text = weight_color.__doc__,
    icon = 'VPAINT_HLT')


def register():
    bpy.utils.register_class(weight_color)      
    bpy.types.VIEW3D_MT_object.append(addObject)

def unregister(): 
    bpy.types.VIEW3D_MT_object.remove(addObject)
    bpy.utils.unregister_class(weight_color)

if __name__ == "__main__":  
    register()

---

any feedback is welcome

example :