Sets a new source mesh to a mesh instance, by manipulating the 'meshInst' and 'source' graphs.

CmdSetMeshInstance.py

################################################################################
#
# SetMeshInstance.py
#
# Version: 0.1
#
# Author: Ivo Grigull
#
# Last Update: 10/06/2015
#
# Usage:
#    Copy this file into the lxserv folder before starting modo
#    Run the script using arguments as in the example below or
#    Select the instance, the new source and run the script without arguments
#
################################################################################

""" Example script usage:

# Create various primitive meshes
lx.eval('script.implicit "Unit Cube Item"')
lx.eval('script.implicit "Unit Sphere Item"')
lx.eval('script.implicit "Unit Toroid Item"')

# Create an instance
lx.eval('item.duplicate instance:true')
lx.eval('item.name Instance meshInst')

# Set the instance source to use the Cube
lx.eval('mesh.setInstance Instance Cube'

"""

import lx
import lxifc
import lxu.command
import modo


def setSourceInstance(instName=None, sourceName=None):
    """Sets a new source mesh to a mesh instance, by manipulating the 'meshInst' and 'source' graphs.

    :param basestring instName: Name of the instance item
    :param basestring instName: Name of the new source mesh item

    If both arguments are None, the selection will be used. Select the instance first and then the new source mesh.
    """

    scene = modo.Scene()

    # If no arguments were passed
    if not all((instName, sourceName)):
        selection = scene.selected
        if not len(selection) == 2:
            return False
        instance, newSource = selection
    else:
        # Try looking the items up using the given names
        try:
            instance = scene.item(instName)
            newSource = scene.item(sourceName)
        except LookupError:
            return False

    # Check for expected types
    if not instance.type == 'meshInst' or not newSource.type == 'mesh':
        return False

    # Now disconnect the existing connection and connect the new source
    # in both graphs respectively

    # meshInst graph
    for source in instance.itemGraph('meshInst'):
        meshInstGraph = instance.itemGraph('meshInst')._graph
        meshInstGraph.DeleteLink(source, instance)
        meshInstGraph.AddLink(newSource, instance)

    # source graph
    for dest in instance.itemGraph('source').forward():
        sourceGraph = instance.itemGraph('source')._graph
        sourceGraph.DeleteLink(instance, dest)
        sourceGraph.AddLink(instance, newSource)

    return True


class CmdSetMeshInstance(lxu.command.BasicCommand):
    def __init__(self):
        lxu.command.BasicCommand.__init__(self)

        self.dyna_Add('instance', lx.symbol.sTYPE_STRING)
        self.basic_SetFlags(0, lx.symbol.fCMDARG_OPTIONAL)

        self.dyna_Add('source', lx.symbol.sTYPE_STRING)
        self.basic_SetFlags(1, lx.symbol.fCMDARG_OPTIONAL)

    def cmd_Flags(self):
        return lx.symbol.fCMD_MODEL | lx.symbol.fCMD_UNDO

    def basic_Enable(self, msg):
        return True

    def cmd_Interact(self):
        pass

    def basic_Execute(self, msg, flags):
        result = True
        if self.dyna_IsSet(0) and self.dyna_IsSet(1):
            nameInstance = self.dyna_String(0, None)
            nameSource = self.dyna_String(1, None)
            result = setSourceInstance(nameInstance, nameSource)
        else:
            result = setSourceInstance()

        message = lx.object.Message(msg)
        message.SetCode (lx.result.OK) if result else message.SetCode (lx.result.ABORT)

        return result

lx.bless(CmdSetMeshInstance, "mesh.setInstance")