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NodeData based classic plugin classes can implement NodeData::SetDParameter(). This allows to change parameters that are set and it allows to react to this event. This is typically done to handle data that is not stored in the object's BaseContainer. It is also used to change parameter values when another parameter was changed.

NodeData::SetDParameter() corresponds to C4DAtom::SetParameter().

In most cases, when implementing NodeData::SetDParameter(), one will also need to implement NodeData::GetDParameter(). For example, if the value is stored in a member variable.


NodeData::SetDParameter() is called when the value of a parameter is set with C4DAtom::SetParameter(). It is possible to change this value before it is stored in the element's BaseContainer.

Bool SetDParameter(GeListNode* node, const DescID& id, const GeData& t_data, DESCFLAGS_SET& flags)
if (!node)
return false;
switch (id[0].id)
// This parameter will not be stored in the BaseContainer
// store the set value in a member variable.
_value = t_data.GetInt32();
// mark parameter as set
// return from the function, don't call the function of the base class.
return true;
// This example sets the value of another parameter based on the value of the given parameter.
const Int32 twice = t_data.GetInt32() * 2;
return SUPER::SetDParameter(node, id, t_data, flags);
Such member variables must also be handled in NodeData::Read(), NodeData::Write(), NodeData::CopyTo() and NodeData::GetDParameter().

The arguments of the function are:

If the parameter is set through user-interaction in the Attribute Manager the message MSG_DESCRIPTION_POSTSETPARAMETER will be sent to the element. See also Interaction.

Certain cases have to be handled with special functions:

It is not safe to call DrawViews() from NodeData::SetDParameter().

Further Reading