[openvrml-develop] Re: Transparency

[Damian M. <da...@er...>]

Christopher St John wrote:

> Sort them once at the begining.  Then resort on every single change in
> viewpoint. Assume that as you move around the list will remain mostly
> sorted, and choose a sorting algorithm to fit that assumption.

If you rotate yourself, say 90 degrees, doesn't the list get horribly out
of sort.  Mind you, this is simply a Z-buffer problem.

> If you hunt around on the net, there are some detailed explanations of
> how it all should work, I seem to remember the SGI Performer docs have
> a discussion.

I'll go fishing.

On the underlying graphics library issues, are there some notes floating
around anywhere on the overall design of the Scene Graph, and how this is
then mapped into the OpenGL library.

I also noticed that there is a significant processing load caused by the
virtual function ViewOpenGL::insertReference which adds a reference into
the call list.  In our test cases, during loading of the large VRML file,
this causes squillions of calls to glCallList().  While a virtual function
can create load, this appears to create nearly half the processing load of
tessShellVertex(), gluTessEndPolygon(), tessShellBegin() & insertShell()
combined so I don't believe it is just the 'virtual'ness of the function.
I'm wondering if there was a way to buffer up these calls, say N at a
time, and send them out in a single call to glCallLists().  Mind you, I
can't see the optimal spot where I would flush out those remaining in the
buffer when the scene was fully interpreted.

Thanks - Damian (McGuckin)

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