GUI_3DPartState
This callback returns state information when the visibility of a 3D part is changed.
Callback Parameters
- PartInfo: 
Part3DObjectcontaining:Part3DObject {
name: string; // Name of part
visible: Boolean; // State of visibility
} 
Example
GUI_3DPartInfo.connect(function(partinfo) {
    if (partinfo.visible) {
        console.log("part is visible");
    } else {
        console.log("part is hidden");
    }
});