Hi Robert,
> By default I would expect it to traverse all children. One variation> I
> considered was to have a NodeMask + StateSet per Child, with this>
> combination you'd be able to select different combinations for> different
> traversal masks.>
If I set up the LayerNode to have one child for each StateSet I want to switch
between, and give each of those children their own node mask. Then I can set up
the cull-mask of my cameras so that they chose the correct StateSet. This will
work fine.
The LayerNode will be more flexible than the StateSetSwitchNode, but I think it
will be a bit slower.
Let's examine traverse performance of the LayerNode and the
StateSetSwitchNode.In this example we assume that we want to switch between 5
different state-sets.I am now only looking at the usage method that the
StateSetSwitchNode supports.
LayerNode:============Cull-traverse will first run the accept function of the
LayerNode. It will then call traverse and call accept for each of the 5
children of the LayerNode. One of the 5 children will pass the mask check and
call its traverse function.
LayerNode will be slower the more StateSet's you want to switch between.
Any traverse with node mask 0xffffffff will traverse each of the 5 children,
and their children
In my case, they share the same children, which can be a whole world.
StateSetSwitchNode:=====================Cull-traverse will call the accept
function of the StateSetSwitchNode. This function is modified and has one extra
bitvise and operation, and one extra array lookup. It then call the traverse
function of the node-pointer it read from the array.That sounds like almost 5
times faster than the LayerNode.
StateSetSwitchNode will not run slower if we add more StateSet's to switch
between.
Any traverse with node mask 0xffffffff will traverse only one of the nodes in
the array and that node's children. All nodes in the array share the same
children, and in this solution they get traversed one time instead of 5.
I feel that I need to state that the StateSetSwitchNode comes with a rule-set:
- Only one of the state-sets shall be traversed during any traversal. - They
shall all point to the same sub-tree (always).These rules are neccessary in
order to make the cull-traverse as fast as possible.
My conclusion after this e-mail is still that I want to implement the
StateSetSwitchNode as an addition to the SwitchNode and a future version of the
LayerNode.It would be very beneficial for me to integrate it to OSG and support
it in the .ive and .osg file formats.I would be happy to contribute a good
example of usage and the OSG implementation if you give a green light to OSG
integration.
Viggo
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