Hello,
This is my first try with mailing-list, I am icecode in IRC, Icecode GL in
forum and a few time ago I've been involved in trying to return shadows
back in FlightGear, exploring the big world of shaders and effects. But
when Z-fighting (http://en.wikipedia.org/wiki/Z-fighting) problem appeared,
I needed glPolygonOffset (
http://www.opengl.org/sdk/docs/man/xhtml/glPolygonOffset.xml). After
reading the OSG documentation (
http://www.openscenegraph.org/documentation/OpenSceneGraphReferenceDocs/a00523.html),
I got this code at Simgear's Effect.cxx:
struct PolygonOffsetBuilder : public PassAttributeBuilder
> {
> void buildAttribute(Effect* effect, Pass* pass, const SGPropertyNode*
> prop,
> const SGReaderWriterXMLOptions* options)
> {
> if (!isAttributeActive(effect, prop))
> return;
>
> const SGPropertyNode* pfactor
> = getEffectPropertyChild(effect, prop, "factor");
> const SGPropertyNode* punits
> = getEffectPropertyChild(effect, prop, "units");
>
> ref_ptr<PolygonOffset> polyoffset = new PolygonOffset;
>
> int factor, units;
>
> if (pfactor)
> factor = pfactor->getIntValue();
> if (punits)
> units = punits->getIntValue();
>
> polyoffset->setFactor(factor);
> polyoffset->setUnits(units);
>
> pass->setAttributeAndModes(polyoffset.get());
> }
> };
>
> InstallAttributeBuilder<PolygonOffsetBuilder>
> installPolygonOffset("polygon-offset");
>
>
I correctly did the #include <osg/PolygonOffset> at the start of file.
Compilation goes OK, but when I run FG, this message appears a couple of
times:
skipping unknown pass attribute polygon-offset
>
What can be the problem? Sorry if it is a silly mistake, but I am a newbie
in the effects things etc. If you want to know anything more about the
shadows, I am trying to implement the shadow volumes (
http://en.wikipedia.org/wiki/Shadow_volume) technique, using stencil. Info
of progress, .vert and .eff at forum topic:
http://www.flightgear.org/forums/viewtopic.php?f=47&t=13648.
Cheers.
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