A small python plug-in for (X)SI. Let's you set RGB or HSV colors. This applies the colors to the first vertex color cluster it finds for every model in the current selection. If it doesn't find a cluster it can create one if you check the Create Cluster option. I created a very basic script for a friend who needed to eliminate baked AO from the…

vertcolchanger.py

# Changes Vertex Color Values.
# This should go to <USER>\\Autodesk\\<Softimage Version>\\Application\\Plugins.
# It's not important how the file is named.
#
# Code Copyright (C) Benedikt Schatz http://schlechtwetterfront.github.com
#
# GNU General Public License http://www.gnu.org/licenses/.
#
# The command will be added to the Get>Property menu.
import colorsys
import os
from win32com.client import constants as const

xsi = Application


def XSILoadPlugin(in_reg):
    in_reg.Author = 'Ande'
    in_reg.Name = 'VertColChanger'
    in_reg.Email = 'schlchtwtrfrnt@gmail.com'
    in_reg.URL = 'https://sites.google.com/site/andescp/'
    in_reg.Major = 1
    in_reg.Minor = 1

    in_reg.RegisterCommand('VertColChanger', 'VertColChanger')
    in_reg.RegisterMenu(const.siMenuTbGetPropertyID, 'Edit Vertex Colors', True)

    return True


def XSIUnloadPlugin(in_reg):
    return True


def EditVertexColors_Init(in_ctxt):
    menu = in_ctxt.Source
    menu.AddCommandItem('Set Vertex Colors', 'VertColChanger')


def VertColChanger_Init(in_ctxt):
    oCmd = in_ctxt.Source
    oCmd.Description = ''
    oCmd.ReturnValue = True

    return True


def VertColChanger_Execute():
    for plugin in xsi.Plugins:
        if plugin.Name == 'VertColChanger':
            path = plugin.OriginPath
    for prop in xsi.ActiveSceneRoot.Properties:
        if prop.Name == 'VertColChanger':
            xsi.DeleteObj('VertColChanger')
    pset = xsi.ActiveSceneRoot.AddProperty('CustomProperty', False, 'VertColChanger')
    pset.AddParameter3('create', const.siBool, False, '', '', 0, 0)
    pset.AddParameter3('colortype', const.siString, 'RGB')
    pset.AddParameter3('red', const.siBool)
    pset.AddParameter3('green', const.siBool)
    pset.AddParameter3('blue', const.siBool)
    pset.AddParameter3('hue', const.siBool, False, '', '', 0, 1)
    pset.AddParameter3('saturation', const.siBool, False, '', '', 0, 1)
    pset.AddParameter3('value', const.siBool, False, '', '', 0, 1)
    pset.AddParameter3('alpha', const.siBool)
    pset.AddParameter3('redv', const.siDouble, 0.0, 0.0, 1.0)
    pset.AddParameter3('greenv', const.siDouble, 0.0, 0.0, 1.0)
    pset.AddParameter3('bluev', const.siDouble, 0.0, 0.0, 1.0)
    pset.AddParameter3('huev', const.siDouble, 0.0, 0.0, 1.0, 0, 1)
    pset.AddParameter3('saturationv', const.siDouble, 0.0, 0.0, 1.0, 0, 1)
    pset.AddParameter3('valuev', const.siDouble, 0.0, 0.0, 1.0, 0, 1)
    pset.AddParameter3('alphav', const.siDouble, 0.0, 0.0, 1.0)
    mlay = pset.PPGLayout
    mlay.SetAttribute(const.siUILogicFile, '{0}\\vertcolchanger.py'.format(path))
    mlay.Language = 'pythonscript'

    agr = mlay.AddGroup
    egr = mlay.EndGroup
    text = mlay.AddStaticText
    item = mlay.AddItem
    arow = mlay.AddRow
    erow = mlay.EndRow

    agr('Vertex Color Changer', 1)
    arow()
    item('create', 'Create Cluster')
    mlay.AddEnumControl('colortype', ('RGB', 'RGB', 'HSV', 'HSV'), 'Color Space', const.siControlRadio)
    btn = mlay.AddButton('change', 'CHANGE!')
    btn.SetAttribute(const.siUICX, 60)
    btn.SetAttribute(const.siUICY, 43)
    erow()
    agr('Colors')

    arow()
    agr('', 0)  # color labels
    text('Red')
    text('Green')
    text('Blue')
    text('Hue')
    text('Saturation')
    text('Value')
    text('Alpha')
    egr()

    ctrlgr = agr('', 0)
    arow()
    red = item('red', '')
    red.SetAttribute('ValueOnly', True)
    redv = item('redv', '')
    redv.SetAttribute('ValueOnly', True)
    erow()
    arow()
    green = item('green', '')
    green.SetAttribute('ValueOnly', True)
    greenv = item('greenv', '')
    greenv.SetAttribute('ValueOnly', True)
    erow()
    arow()
    blue = item('blue', '')
    blue.SetAttribute('ValueOnly', True)
    bluev = item('bluev', '')
    bluev.SetAttribute('ValueOnly', True)
    erow()

    arow()
    hue = item('hue', '')
    hue.SetAttribute('ValueOnly', True)
    huev = item('huev', '')
    huev.SetAttribute('ValueOnly', True)
    erow()
    arow()
    saturation = item('saturation', '')
    saturation.SetAttribute('ValueOnly', True)
    saturationv = item('saturationv', '')
    saturationv.SetAttribute('ValueOnly', True)
    erow()
    arow()
    value = item('value', '')
    value.SetAttribute('ValueOnly', True)
    valuev = item('valuev', '')
    valuev.SetAttribute('ValueOnly', True)
    erow()

    arow()
    alpha = item('alpha', '')
    alpha.SetAttribute('ValueOnly', True)
    alphav = item('alphav', '')
    alphav.SetAttribute('ValueOnly', True)
    erow()
    egr()
    ctrlgr.SetAttribute('WidthPercentage', 90)
    erow()
    egr()
    egr()

    xsi.InspectObj(pset, '', '', 'siLock')

    return True


def colortype_OnChanged():
    ppg = PPG.Inspected(0)
    if ppg.Parameters('colortype').Value == 'RGB':
        ppg.Parameters('red').ReadOnly = False
        ppg.Parameters('redv').ReadOnly = False
        ppg.Parameters('green').ReadOnly = False
        ppg.Parameters('greenv').ReadOnly = False
        ppg.Parameters('blue').ReadOnly = False
        ppg.Parameters('bluev').ReadOnly = False
        ppg.Parameters('hue').ReadOnly = True
        ppg.Parameters('huev').ReadOnly = True
        ppg.Parameters('saturation').ReadOnly = True
        ppg.Parameters('saturationv').ReadOnly = True
        ppg.Parameters('value').ReadOnly = True
        ppg.Parameters('valuev').ReadOnly = True
    else:
        ppg.Parameters('red').ReadOnly = True
        ppg.Parameters('redv').ReadOnly = True
        ppg.Parameters('green').ReadOnly = True
        ppg.Parameters('greenv').ReadOnly = True
        ppg.Parameters('blue').ReadOnly = True
        ppg.Parameters('bluev').ReadOnly = True
        ppg.Parameters('hue').ReadOnly = False
        ppg.Parameters('huev').ReadOnly = False
        ppg.Parameters('saturation').ReadOnly = False
        ppg.Parameters('saturationv').ReadOnly = False
        ppg.Parameters('value').ReadOnly = False
        ppg.Parameters('valuev').ReadOnly = False


def change_OnClicked():
    ppg = PPG.Inspected(0)
    if ppg.Parameters('colortype').Value == 'RGB':
        change_rgb(ppg)
    else:
        change_hsv(ppg)


def change_rgb(ppg):
    pb = XSIUIToolkit.ProgressBar
    pb.Value = 0
    pb.Maximum = 1
    pb.Caption = 'Preparing...'
    pb.Visible = True
    param = ppg.Parameters
    dored = param('red').Value
    dogreen = param('green').Value
    doblue = param('blue').Value
    doalpha = param('alpha').Value
    if dored:
        red = param('redv').Value
    if dogreen:
        green = param('greenv').Value
    if doblue:
        blue = param('bluev').Value
    if doalpha:
        alpha = param('alphav').Value
    pb.Increment()
    sel = xsi.Selection
    everything = [mdl for mdl in sel]
    pb.Value = 0
    pb.Maximum = len(everything)
    for mdl in everything:
        pb.Caption = 'Changing Colors for {0}...'.format(mdl.Name)
        vertcol = get_cluster(mdl)
        if not vertcol:
            if param('create').Value:
                xsi.CreateVertexColorSupport()
                vertcol = get_cluster(mdl)
            else:
                XSIUIToolkit.MsgBox('Couldnt find vertex colors for {0}. Aborting.'.format(mdl.Name), 0, 'Vertex Color Changer')
                return
        els = vertcol.Elements.Array
        numverts = len(els[0])
        if dored and dogreen and doblue and doalpha:
            newels = [[red] * numverts, [green] * numverts, [blue] * numverts, [alpha] * numverts]
            vertcol.Elements.Array = newels
            return
        newels = [[], [], [], []]
        for n in xrange(numverts):
            r, g, b, a = els[0][n], els[1][n], els[2][n], els[3][n]
            if dored:
                r = red
            if dogreen:
                g = green
            if doblue:
                b = blue
            if doalpha:
                a = alpha
            newels[0].append(r)
            newels[1].append(g)
            newels[2].append(b)
            newels[3].append(a)
        vertcol.Elements.Array = newels
        pb.Increment()


def change_hsv(ppg):
    pb = XSIUIToolkit.ProgressBar
    pb.Value = 0
    pb.Maximum = 1
    pb.Caption = 'Preparing...'
    pb.Visible = True
    param = ppg.Parameters
    dohue = param('hue').Value
    dosaturation = param('saturation').Value
    dovalue = param('value').Value
    doalpha = param('alpha').Value
    if dohue:
        hue = param('huev').Value
    if dosaturation:
        saturation = param('saturationv').Value
    if dovalue:
        value = param('valuev').Value
    if doalpha:
        alpha = param('alphav').Value
    pb.Increment()
    sel = xsi.Selection
    everything = [mdl for mdl in sel]
    pb.Value = 0
    pb.Maximum = len(everything)
    for mdl in everything:
        pb.Caption = 'Changing Colors for {0}...'.format(mdl.Name)
        vertcol = get_cluster(mdl)
        if not vertcol:
            if param('create').Value:
                xsi.CreateVertexColorSupport()
                vertcol = get_cluster(mdl)
            else:
                XSIUIToolkit.MsgBox('Couldnt find vertex colors for {0}. Aborting.'.format(mdl.Name), 0, 'Vertex Color Changer')
                return
        els = vertcol.Elements.Array
        numverts = len(els[0])
        newels = [[], [], [], []]
        for n in xrange(numverts):
            r, g, b, a = els[0][n], els[1][n], els[2][n], els[3][n]
            h, s, v = colorsys.rgb_to_hsv(r, g, b)
            if dohue:
                h = hue
            if dosaturation:
                s = saturation
            if dovalue:
                v = value
            if doalpha:
                a = alpha
            r, g, b = colorsys.hsv_to_rgb(h, s, v)
            newels[0].append(r)
            newels[1].append(g)
            newels[2].append(b)
            newels[3].append(a)
        vertcol.Elements.Array = newels
        pb.Increment()


def do_stuff():
    sel = xsi.Selection(0)
    everything = get_all_children(sel)
    for mdl in everything:
        vertcol = get_cluster(mdl)
        els = vertcol.Elements.Array
        # print els
        numverts = len(els[0])
        newels = [[], [], [], [1.0] * numverts]
        for n in xrange(numverts):
            # print 'rgb xsi', els[0][n], els[1][n], els[2][n]
            h, s, v = colorsys.rgb_to_hsv(els[0][n], els[1][n], els[2][n])
            # print 'hsv', h, s, v
            v = .5
            r, g, b = colorsys.hsv_to_rgb(h, s, v)
            # print 'rgb', r, g, b
            newels[0].append(r)
            newels[1].append(g)
            newels[2].append(b)
        vertcol.Elements.Array = newels
        # print newels
    return True


def get_all_children(root):
    '''Recursively adds children to a list.'''
    children = []
    children.append(root)
    if root.Children(0):
        chldrn = list(root.Children)
        for child in chldrn:
            children.extend(get_all_children(child))
    return children


def get_cluster(model):
    geo = model.ActivePrimitive.GetGeometry2(0)
    sample_clusters = geo.Clusters.Filter('sample')
    for cls in sample_clusters:
        for prop in cls.Properties:
            if prop.Type == 'vertexcolor':
                return prop