ok, well. I guess i have to find another way.
is there a way for a tag plugin to notice, that the object it is on has changed within the hierarchy? like the MSG_CHANGE? That could help me 
Unsolved Detect Hirarchy Change in a tag
Hi @cgweasel I forked your topic, in the future please create a new topic each time you have a question with a topic that is unrelated to the current discussion.
With that said there is no 100% reliable way to do it, the best way would be to store the neighbor hierarchy (GetUp,GetPred,GetNext) and then add an execution step as Initial so within the Execute method you can check for these objects.
Find bellow and example adapted from py-look-at-camera example. The important methods to check are:
__init__to initialize the cache valueAddToExecutionto add the Initial state executionisHierarchyChangedto check if the cache changedupdateCachedHierarchyto update the cacheExecutewithpriority == c4d.EXECUTIONPRIORITY_INITIALthat will check the cache, and print a message when the hierarchy changed.
import os
import c4d
# Be sure to use a unique ID obtained from www.plugincafe.com
PLUGIN_ID = 1028284
class LookAtCamera(c4d.plugins.TagData):
"""Look at Camera"""
def __init__(self):
self._up = None
self._pred = None
self._next = None
def Init(self, node):
"""Called when Cinema 4D Initialize the TagData (used to define, default values).
Args:
node (c4d.GeListNode): The instance of the TagData.
Returns:
True on success, otherwise False.
"""
self.InitAttr(node, bool, c4d.PYLOOKATCAMERA_PITCH)
node[c4d.PYLOOKATCAMERA_PITCH] = True
pd = c4d.PriorityData()
if pd is None:
raise MemoryError("Failed to create a priority data.")
pd.SetPriorityValue(c4d.PRIORITYVALUE_CAMERADEPENDENT, True)
node[c4d.EXPRESSION_PRIORITY] = pd
return True
def AddToExecution(self, tag, prioList):
"""Called By Cinema 4D to determine when in the Execution Pipeline the Execute method of this tag should be called.
Args:
tag (c4d.BaseTag): The instance of the TagData.
prioList (c4d.plugins.PriorityList): The priority list to add your tag’s execution points to.
Returns:
True if the hierarchy changed, otherwise False.
"""
# Retrieve the user defined priority
storedPriority = tag[c4d.EXPRESSION_PRIORITY]
storedPriorityValue = storedPriority.GetPriorityValue(c4d.PRIORITYVALUE_MODE) + \
storedPriority.GetPriorityValue(c4d.PRIORITYVALUE_PRIORITY)
# Add an execution during the Initial phase, this is when we will check for hierarchy change
prioList.Add(tag, c4d.EXECUTIONPRIORITY_INITIAL, 0)
# Add the user defined execution phase, therefor the Execute method will be called 2 times.
prioList.Add(tag, storedPriorityValue, 0)
return True
def isHierarchyChanged(self, obj):
"""Check if any of the cached neighbor hierarchy is different from the actual one.
Args:
obj (c4d.BaseObject): The host object to compare the hierarchy from.
Returns:
True if the hierarchy changed, otherwise False.
"""
up = obj.GetUp()
if up != self._up:
return True
pred = obj.GetPred()
if pred != self._pred:
return True
next = obj.GetNext()
if next != self._next:
return True
return False
def updateCachedHierarchy(self, obj):
"""Update the cached neighbor hierarchy.
Args:
obj (c4d.BaseObject): The host object to retrieve the hierarchy from.
"""
self._up = obj.GetUp()
self._pred = obj.GetPred()
self._next = obj.GetNext()
def Execute(self, tag, doc, op, bt, priority, flags):
"""Called by Cinema 4D at each Scene Execution, this is the place where calculation should take place.
Args:
tag (c4d.BaseTag): The instance of the TagData.
doc (c4d.documents.BaseDocument): The host document of the tag's object.
op (c4d.BaseObject): The host object of the tag.
bt (c4d.threading.BaseThread): The Thread that execute the this TagData.
priority (EXECUTIONPRIORITY): Information about the execution priority of this TagData.
flags (EXECUTIONFLAGS): Information about when this TagData is executed.
"""
if priority == c4d.EXECUTIONPRIORITY_INITIAL:
if self.isHierarchyChanged(op):
self.updateCachedHierarchy(op)
print("Hierarchy Changed")
# We don't want to execute the logic of our tag during this phase except if the user asked for it
storedPriority = tag[c4d.EXPRESSION_PRIORITY]
storedPriorityValue = storedPriority.GetPriorityValue(c4d.PRIORITYVALUE_MODE) + \
storedPriority.GetPriorityValue(c4d.PRIORITYVALUE_PRIORITY)
if storedPriorityValue != c4d.EXECUTIONPRIORITY_INITIAL:
return c4d.EXECUTIONRESULT_OK
# Retrieves the current active base draw
bd = doc.GetRenderBaseDraw()
if bd is None:
return c4d.EXECUTIONRESULT_OK
# Retrieves the active camera
cp = bd.GetSceneCamera(doc) if bd.GetSceneCamera(doc) is not None else bd.GetEditorCamera()
if cp is None:
return c4d.EXECUTIONRESULT_OK
# Calculates the position to target
local = cp.GetMg().off * (~(op.GetUpMg() * op.GetFrozenMln())) - op.GetRelPos()
# Calculates the rotation to target
hpb = c4d.utils.VectorToHPB(local)
if not tag[c4d.PYLOOKATCAMERA_PITCH]:
hpb.y = op.GetRelRot().y
hpb.z = op.GetRelRot().z
# Defines the rotation
op.SetRelRot(hpb)
return c4d.EXECUTIONRESULT_OK
if __name__ == "__main__":
# Retrieves the icon path
directory, _ = os.path.split(__file__)
fn = os.path.join(directory, "res", "tpylookatcamera.tif")
# Creates a BaseBitmap
bmp = c4d.bitmaps.BaseBitmap()
if bmp is None:
raise MemoryError("Failed to create a BaseBitmap.")
# Init the BaseBitmap with the icon
if bmp.InitWith(fn)[0] != c4d.IMAGERESULT_OK:
raise MemoryError("Failed to initialize the BaseBitmap.")
c4d.plugins.RegisterTagPlugin(id=PLUGIN_ID,
str="Py - LookAtCamera",
info=c4d.TAG_EXPRESSION | c4d.TAG_VISIBLE,
g=LookAtCamera,
description="Tpylookatcamera",
icon=bmp)
Side note, we will be away the 26th and 27th December, so don't be surprise by the delay if you have follow-up questions, for more information see No support on 26/12 and 27/12.
Cheers,
Maxime.
MAXON SDK Specialist