Body center calculation in Export Placement

Export Placement offers three choices for Placement Origin - Symbol Origin, Body Center, and Pin 1. My question is in reference to the Body Center option. If body center is based on the symbol origin, how is this different from the Symbol Origin option?

Example.  A through-hole connector should normally have its symbol origin on pin 1.   If you were to choose body center instead it would calculate the geometric mean of the all the pins on the symbol and export those coordinates.

On a typical IC, the body center and symbol origin are the same.

The Body Center calculation is based on the following priority:

1. Text String location on Package Geometry/Body_Center
2. Centroid of the Shape defined on Package Geometry/Place_Bound_Top
3. Centroid of the Shape defined on Package Geometry/Dfa_Bound_Top, if Place_Bound_Top shape does not exist
4. Centroid of the gathering of pins in the symbol, If Dfa_Bound_Top and Place_Bound_Top shapes do not exist

For odd shaped components you may want to define a Text String on Package Geometry/Body_Center in your symbol to ensure that the Body Center calculation is what you expect.  If you want to see where Allegro thinks the Body Center of a symbol is located you could move the symbol with the "Point" set to "Body Center" under the Options tab.  You could then delete the shapes mentioned above and move the symbol again to see how the Body Center calculation changes.

Symbol Origin is the 0,0 inside of the symbol, nothing more, and not to be confused with Body Center.  In most cases SMD symbols will have the Symbol Origin at the Body Center of the component, as mentioned on another post

Hope this helps,
Mike Catrambone