RE: [Plib-devel] Texture and blend modes

[Norman V. <nh...@ca...>]

Steve Baker writes:
>
>"Curtis L. Olson" wrote:
>
>> Hmmm, yes, for flightgear, there are a couple things I'd like to see
>> added to ssg's lazy state evaluator ...
>
>What - specifically?
>
>> Let me jump in here and say that I'm not exactly 100% pleased with
>> handling these things via a call back function.  The call back has no
>> way to know the initial state of the element you are interested in
>> changing.  So, how do you reliably restore the value?  How do you know
>> if you need to actually change the state or not?  You are back to all
>> the problems associated with randomly changing state at random points
>> in your program ... these are the sorts of problems ssgSimpleState was
>> designed to fix.
>
>Well, that's why you have to decide which things to test before EVERY
>leaf node is drawn - and which to set and restore in callbacks.

A slightly different but related question.

Is it possible to design a branch node that does some of this ?

By this I mean that I know that everything below this node
will share a common property.  Hence short circuting some state
change tests at the leaf level for all deeper nodes.

This would allow programs such as flightgear that use
a higher level bucketing mechanism then OpenGL primitives
to minimize state changing when traversing the tree

I can envision a similar node type being used for compiled vertex arrays,

simplistically

            bucket node  ( lock vertices and set transform here when
entering bucket )
              /     |      \          ( if node passes Bounding Sphere
test )
            /       |        \
     mat1     mat2    mat3  ( set display states here )
                 /  |  \               ( should these nodes have Bounding
Spheres  ?)
               /    |    \
         Fan  Fan  Strip      ( set texture coordinates and Fine grained BS
based Display )

Maybe just a 'short-circut-me' bit in the SimpleState
and a would allow this

Does this make any sense ??

Norman