SET_VP_VIEW_MODE specifies whether the viewport is in parallel
viewing mode or perspective viewing mode.
--->(SET_VP_VIEW_MODE)--|viewport|--+--(:PARALLEL)-----+-->
| |
+--(:PERSPECTIVE)--+
The following options are available to set the view mode.
- :PARALLEL - specifies parallel viewing (this is the default).
- :PERSPECTIVE - specifies perspective viewing.
Use this action to view a part in perspective.