Hi Chris,
Robert Osfield wrote:
Second important issue for me is usage of _name in scene graph. I always
expected that _name is reserved for users and its a normal rule in all
Scene
Graph implementations that libraries do not change it. Names are
ususlly
used to identify certain portions of models and hook up the code
properly.
Thats something that provide standard linking mechanisms between artists
and
programmers works.
I agree, but... in this instance the DatabasePager's algorithm was
about deleting a subgraph that would no longer have any role to play
in the applications life so the changing of name should never have got
outside that algorithm as the subgraph would be just deleted. So it
is in theory just a black box, how it does it's job shouldn't effect
anything else. Alas in this case it looks like the algorithm in
DatabasePager is flawed.
This is the part that I couldn't tell from a simple reading of the code.
Once a node is
renamed to "NeedToRemove", under normal circumstances (ignoring the cache
trick above), is
there any possibility that that node can "return to life"? It sounds like
you're saying
there is no possibility, in which case I sort of agree with Robert that
altering the name
is fair game, as the node is now "the walking dead" and anything is
permissible.
I disagree, when Scene is available in update traversal for various visitors
you could expect that some user may want to do some specific decoration of
the PageLOD node. Modify texture attributes, attach some objects etc. So
once you allowed user to get to PagedLOD via update traversal vistiors you
should expect that this PagedLOD ref_count increases. In such case
DatabasePager should not longer assume it posses this node completely.
Other case could be following. We overrite ReadFileCallback and generate and
reuse some procedural generic tile (for example spherical sector of ocean
mesh). This is again a case where PageLOD is not directly loaded by
DatabasePager but only used by it. So DatabasePager should behave politely
with this node...
Cheers,
Wojtek
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