How to dynamically hide parameters

[kng_ito]

Hi,

I am trying to control which parameters of ObjectPlugin are shown/hidden depending on the values of another parameter.
For example, the Cloner object switches which parameters it displays depending on its "mode" parameter.

From the other threads I see that overriding GetDDescription() is the key to achieving this, but I just can't get it to work.

Any help would be appreciated.

[ferdinand]

Hello @kng_ito,

Thank you for reaching out to us. Modifying the description of a node via NodeData.GetDDescription should only be done when NodeData.GetDEnabling is not sufficient. To hide a parameter, the field c4d.DESC_HIDE must be set to True. Find a simple example below.

Cheers,
Ferdinand

Result:

File: pc14487.zip

Code:

// The description defintion of the tag Texample.
CONTAINER Texample
{
  NAME Texample;
  INCLUDE Texpression;

  // The main "Tag" tab of the tag.
  GROUP ID_TAGPROPERTIES
  {
    // The element which is being hidden (or not).
    REAL ID_HIDDEN_ELEMENT { MIN 0.0; MAX 100.0; UNIT METER; STEP 0.001; CUSTOMGUI REALSLIDER; }
    // The parameter based on which the hidden element is shown or not.
    BOOL ID_HIDE_CONDITION {}
  }
}

"""Implements a tag which dynamically hides and shows a parameter.
"""
import c4d
import typing

class ExampleTagData(c4d.plugins.TagData):
    """Implements a tag which dynamically hides and shows a parameter.
    """
    # The plugin ID for the hook.
    ID_PLUGIN: int = 1060794

    @classmethod
    def Register(cls) -> None:
        """Registers the plugin hook.
        """
        if not c4d.plugins.RegisterTagPlugin(
                id=cls.ID_PLUGIN,
                str="Example Tag",
                info=c4d.TAG_EXPRESSION | c4d.TAG_VISIBLE,
                g=cls, 
                description="texample",
                icon=c4d.bitmaps.InitResourceBitmap(c4d.Tdisplay)):
            print(f"Warning: Failed to register '{cls}' tag plugin.")
        
    def Init(self, node: c4d.GeListNode) -> bool:
        """Called to initialize a tag instance.

        Args:
            node: The BaseTag instance representing this plugin object.
        """
        self.InitAttr(node, float, c4d.ID_HIDDEN_ELEMENT)
        self.InitAttr(node, bool, c4d.ID_HIDE_CONDITION)

        node[c4d.ID_HIDDEN_ELEMENT] = 50.0
        node[c4d.ID_HIDE_CONDITION] = False

        return True

    def Execute(self, tag: c4d.BaseTag, doc: c4d.documents.BaseDocument, op: c4d.BaseObject,
                bt: c4d.threading.BaseThread, priority: int, flags: int) -> int:
        """Called when expressions are evaluated to let a tag modify a scene.

        Not used in this case.
        """
        return c4d.EXECUTIONRESULT_OK

    def GetDDescription(self, node: c4d.GeListNode, description: c4d.Description, 
                        flags: int) -> typing.Union[bool, tuple[bool, int]]:
        """Called by Cinema 4D when the description of a node is being evaluated to let the node
        dynamically modify its own description.
        """
        # Bail when the description cannot be not fully loaded.
        if not description.LoadDescription(node.GetType()):
            return False, flags

        # Define the ID of the parameter we want to modify and get the ID of the parameter which is
        # currently to be evaluated.
        paramId: c4d.DescID = c4d.DescID(c4d.DescLevel(c4d.ID_HIDDEN_ELEMENT, c4d.DTYPE_REAL, 0))
        evalId: c4d.DescID = description.GetSingleDescID()

        # Bail when there is a to be evaluated parameter and our parameter is not part of or equal
        # to the evaluated parameter.
        if (evalId and not paramId.IsPartOf(evalId)):
            return True, flags

        # Get the description data container instance (GetParameter>I<) for the parameter we want to
        # modify. All changes made to the container will be directly reflected on the node. 
        paramData: c4d.BaseContainer = description.GetParameterI(paramId)
        if paramData is None:
            return True, flags

        # Set the hidden state of the parameter ID_HIDDEN_ELEMENT based on the value of the 
        # parameter ID_HIDE_CONDITION.
        paramData[c4d.DESC_HIDE] = node[c4d.ID_HIDE_CONDITION]

        return True, flags | c4d.DESCFLAGS_DESC_LOADED


if __name__ == "__main__":
    ExampleTagData.Register()