Hi all, I have an issue with order of rendering.
I do know that OSG has rendering bins to provide the order of rendering, and
that, inside a rendering bin, it optimizes drawing by sorting objects to render
WRT the state sets.
That's fine. But now I have an use case that I don't know how to implement.
My graphic object is made by a 2D rectangular box with a text on top, as shown
in the picture a).
Well, I do have many of them, which can overlap. I do disable depth test when I
render them, because I want the last one to cover completely the others, when
overlapping.
The visualization that I want to achieve is that shown in picture b).
In order to do that, my scenegraph is made by these nodes:
Main root node
| |
Transf1 Transf2
| | | |
Box1 | Box2 |
| |
Text1 Text2
Transf1 sets the position of Object1
Trasnf2 sets the position of Object2.
Box1 is a geode that contains a drawable that render the rectangular box for
Object1.
Text1 is a text drawable for the text on top of the box1.
Box2 is a geode that contains a drawable that render the rectangular box for
Object2.
Text2 is a text drawable for the text on top of the box2.
So, my objects should be rendered in this order, to draw what I want:
Box1, Text1, Box2, Text2, ...
I do have hundreds of graphic objects like those.
So, how can I do this?
I cannot set the same rendering bin for all Boxes, and a different rendering
bin for all Texts, because OSG would render first all the boxes, and then all
texts, which would overlap each other, like in picture c). Orrible!!!
So, I thought that I have to assign the same rendering bin to all Transf, in
order to make it render all my objects in the same bin, but I have to specify
somehow that it has to render Box and Text in that order for each sub-graph,
instead of optimizing rendering by state set order, which breaks my requirement.
I would need to set some "offset" in rendering bins for Boxes and Texts (1 and
2 respectively), to force OSG to render the Box and Text in that order, for
each subgraph connected to Transf.
It seems an easy thing to do, and mine seems a silly question, but I cannot do
that.
Any help is appreciated.
Thanks,
Gianluca
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