as we all know, Maya is node based.
We can edit nodes in the history of a dag node, the changes will flow through the network and finally change that dag node somehow.
But there`s the Maya concept of how to deal with component data which totally destroys automatic data update.
Two shapes with individual shaders are combined with the help of the polyUnite node. Maya automatically creates groupPart and groupId nodes which help the shaders in detecting the faces of the new object. Unfortunately, the face information is written in the groupParts nodes right when they are created and never automatically updated.
So, when the geometry of the initial shapes is changed, the groupParts keep the old information and thus the shading of the new shape is wrong.
Obviously, the only non API method ( I did not check whether the API functions could help here ) is to create with MEL a string holding the new face data and push it into the groupParts node.
Of course, this is very odd. No more automatic DG update possible.
Moreover, when the face count becomes too large ( well, not so large actually, but for MEL ), it takes endless to apply the string with the face data to the groupParts node ( as is the case with every too long string which you would want to enter into a node with MEL.
So, here`s the question:
Are there methods I do not know of which help in interactive updating of that component data?
Otherwise, I would write a request in the autodesk feedback ideas forum..