Hello Mauro,
Mauro Mithrandir wrote:
> I'm using a SimpleSceneManager (inside a QGLWidget) to manage a scene that
> contains a transparent object. The problem is that I can't obtain a proper
> rendering. I'm working on Linux with the latest OpenSG (rev. 2464).
>
> I'm not so familiar with OpenSG 2.0. I remember that in the 1.8 release was
> necessary to set ZWriteTrans and SortTrans to true inside the RenderAction.
sorting transparent objects is the default. ZWriteTrans is off by
default, because sorting only happens at the object level not for
individual triangles [1].
If part of an object is covered by another object the covered part
completely disappears when writing to the depth buffer. If depth writes
are off you still have a chance to obtain correct blending, but it
depends on the drawing order, that's why by default depth writes are off
for transparent objects.
> For setting ZWriteTrans and SortTrans I'm using this code:
>
> ract = OSG::RenderAction::create();
> OSG::RenderOptionsRefPtr options = OSG::RenderOptions::create();
> options->setZWriteTrans(true);
> options->setSortTrans(true);
> options->activate(ract);
> // ract->setZWriteTrans(true); (?)
> sceneManager->setAction(ract);
the RenderOptions are broken at the moment, but calling
ract->setZWriteTrans() directly works since r2462.
> Then I've added a BlendChunk to the object's material:
>
> OSG::BlendChunkRefPtr blendChunk = OSG::BlendChunk::create();
> blendChunk->setSrcFactor(GL_SRC_ALPHA);
> blendChunk->setDestFactor(GL_ONE_MINUS_SRC_ALPHA);
> chunkMaterial->addChunk(blendChunk);
>
> But still transparency is not working properly.
Can you upload a screenshot and post a link to it? It is often much
easier to understand transparency problem when one can see what is going
wrong ;)
Cheers,
Carsten
[1] Only sorting objects not triangles means there are limitations to
how precise blending can be done.
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