[Opensim-dev] SOG/SOP

[Sean Dague]

Michael Wright wrote:
> Well where it gets complicated is when all the children need to have references to their parents. So that the proper positions etc can be set.
> 
> That was another task of the SOG, to keep track of the children and make sure the correct position etc were resolved for the children. 
> 
> What we had before the current SOG/SOP was a  SceneObject that could have child SceneObjects. But it got very complicated. But again its likely that was due as much to the implementation, as to the idea. 
> 
> But its actually been a while since I've had a really good look at the current SOG/SOP so I guess I should do that and see exactly what is happening where, before I comment too much.
> 
> I think one thing we all agree on is that the current setup has problems and there has to be a better way of doing it.

The rel/absolute bits (pos, vel, acc, rot, ang vel) seem to be the crux
of why that back reference is needed.  And the crux of why we need to do
it that way today is that we determine absolute position on read of an
attribute.

If we change the problem around and calculate them on write of a parent
attribute (i.e. obj.Position triggers a cascade of changes to set it's
children's AbsolutePosition), I think we can get rid of the back
reference.  It also has the added benefit of making the read case just
reading existing attributes, and take the cost of the reference frame
change on the write case, which seems a more logical place to impose
that tax.

	-Sean

-- 
Sean Dague / Neas Bade
sdague at gmail.com
http://dague.net


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