viewer: doc++.

doc/viewer.dox

@@ -246,7 +246,9 @@ When the import is done, we clear all material data (as they were copied into
 object instances) and free all unreferenced data by calling
 @ref ResourceManager::free(). Note that we're not doing that for buffers, as
 they are referenced only internally from Mesh and thus the manager would free
-them all, causing dangling memory references and crash later.
+them all, causing dangling memory references and crash later. Better solution
+might be to filter-out the unused data before actually importing them, but
+that's out of scope of this example.
 @dontinclude viewer/ViewerExample.cpp
 @skip _resourceManager.setFallback<Trade::PhongMaterialData>(nullptr)
 @until .free<Mesh>();