It is not possible to convert a Gantt Chart into a resource histogram.
A Gantt Chart is *not* a resource histogram and can never be. They are
two different things.
If by a resource histogram you mean you want to see a graph of resource
work (or other measure) as the ordinate and time as the abscissa, you
can tell Project to do this. There are many ways.
One way:
Menu: Window/Split
Right mouse click into upper window, Menu: View/Resource Sheet
Right mouse click into lower window, Menu: View/Resource Graph
To get finer control over what resources are displayed and how
displayed, right mouse click on the graph, pick "Bar Styles ..." which
provides a lot of capability.
See
http://project.mvps.org/faqs.htm#Combined Resource Graph for a
quick introduction to all this. The best learning is achieved by giving
it a try.
--rms
www.rmschneider.com