Houdini internally supports a number of handles, such as the translate handle or the paint handle that allows geometry to be painted. These handles do not function by default in the host environment. It is up to Houdini Engine plugin writer to add support for each type of handle as required or use some capability within the host environment (such as the ability to paint on meshes) to do something similar to what the handle does. Nevertheless, Houdini Engine provides some basic functionality to query which Houdini handles have been exposed on an asset so that an appropriate error may be printed in case that the handle isn't supported in the host environment.