P.S.: I don't pretend to understand any of this. Render bins and render
bin details are one of the more confusing parts of OSG... I generally
just keep monkeying with them until something sticks.
I will point out that in my understanding, the render bin number and the
render bin details are not tightly related like one might think. It's
not like there's a fixed array of bins somewhere. As I recall, bin
number controls rendering order locally to that part of the scene graph.
Render bin details define how to sort/render things within that local
bin. So if child 1 is render bin 1 it will be rendered before child 2
at render bin 2. The parent node might be render bin 25 and it's
irrelevant. I think.
Though as soon as I pretend I understand that I've had it bite me. So I
could be somewhat wrong somewhere.
-Paul
Paul Speed wrote:
Even within the transparent bin you can enforce specific ordering with
the bin number. Lower numbers get rendered before higher numbers.
I'd have to dig to find any of my own example code but I hoped perhaps
the hint would be enough in short time.
We did this all the time to render double-side transparent geometry.
Draw the inner faces in a lower bin number than the outer faces. Even
with different bin numbers you can still depth sort them.
We had semi-transparent glass boxes with text on the sides. I think we
ultimately had three different bin numbers we used for that associated
with the inner, outer, and text geometries.
-Paul
Jason Daly wrote:
Rabbi Robinson wrote:
Hi,
Is there anyway that I can enforce drawing the objects inside first
before drawing the outside membrane?
Sure, just use setRenderBinDetails() to set a render bin for the
membrane that has a higher number than the render bin used by the
interior objects. For the other parameter, you can set either
"DefaultBin" for a state-sorted bin, or "DepthSortedBin" for a
depth-sorted bin.
interiorStateSet->setRenderBinDetails(0, "DefaultBin");
membraneStateSet->setRenderBinDetails(10, "DepthSortedBin");
However, this is equivalent to this code:
interiorStateSet->setRenderingHint(StateSet::OPAQUE_BIN);
membraneStateSet->setRenderingHint(StateSet::TRANSPARENT_BIN);
Which is probably close to what you're already doing. The problem is
that the transparent geometry still has to obey the depth (z-buffer)
test, even if it's drawn last. You can try disabling the depth test,
but this is likely to cause other problems (if you ever have anything
move in front of the membrane, for example):
depth = new Depth();
depth->setFunction(Depth::ALWAYS);
membraneStateSet->setAttributeAndModes(depth, StateAttribute::ON);
This is the main reason why the alpha to coverage method is sometimes
used, even though it's a bit expensive in draw time.
--"J"
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