Mass Properties

The IMassProperty object:

• allows applications to directly access individual mass properties as found on the Mass Properties dialog box.

• allows applications to override the following properties as found on the Override Mass Properties dialog box:

  • mass
  • center of mass
  • principal axes and principal moments of inertia
  • reference frame and moments of inertia

• obtains mass property information about one or more solid bodies in the document from which the IMassProperty object is obtained.

Only use solid bodies for mass property calculations. You can specify the coordinate system about which the moments is calculated using IMassProperty::SetCoordinateSystem. If you do not use IMassProperty::SetCoordinateSystem, then the document’s origin is the coordinate system. By default, system units (meters, radians, and grams) are used. All properties returning a value are adjusted accordingly. See IMassProperty::UseSystemUnits for more information.

The results of the mass property calculations vary based on whether or not IMassProperty::AddBodies or IMassProperty::IAddBodies is used.  

If the document from which the IMassProperty object came is an assembly, then any body from any of the child components can be used. When obtaining the body, a call to IComponent2::GetBodies2 is needed. Your application does not need to make a copy of the body or apply a transform to the body.