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Timestamp:
09/04/15 17:35:24 (23 hours ago)
Author:
robert
Message:

From Jannik Heller, "I've hit what I believe to be a bug (or at the very least, an unintuitive behaviour) in the osg::Geometry copy constructor. I noticed it when using osg::clone on a Geometry with vertex buffer objects, and the copy flags DEEP_COPY_ARRAYS. To be precise, I add a Geometry to an osgUtil::IncrementalCompileOperation?, then osg::clone the Geometry. I was getting reports from users of random crashes happening.

I believe the offending lines are in the osg::Geometry copy constructor:

if ((copyop.getCopyFlags() & osg::CopyOp::DEEP_COPY_ARRAYS))
{

if (_useVertexBufferObjects)
{

// copying of arrays doesn't set up buffer objects so we'll need to force
// Geometry to assign these, we'll do this by switching off VBO's then renabling them.
setUseVertexBufferObjects(false);
setUseVertexBufferObjects(true);

}

}

Toggling the vertex buffer objects off then on again actually touches not only the arrays controlled by DEEP_COPY_ARRAYS, but also the PrimitiveSets? which are controlled by DEEP_COPY_PRIMITIVES. This means if the user has copyflags of only DEEP_COPY_ARRAYS, we are modifying arrays that belong to the original const Geometry& we are copying from. I believe this shouldn't be allowed to happen because we are using a const& specifier for the original Geometry.

In my case the osgUtil::IncrementalCompileOperation? was trying to compile the geometry, while in the main thread a clone operation toggled the VBO's off and on, a crash ensues.

In the attached patch, you will find a more efficient handling of VBO's in the osg::Geometry copy constructor, so that only the Arrays that were actually deep copied have their VBO assigned, and no changes are made to Arrays that already had a valid VBO assigned. In addition, the DEEP_COPY_PRIMITIVES flag is now honored so that VBO's are set up correctly should a user copy a Geometry with only that flag.
"

Files:
1 modified

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  • OpenSceneGraph/trunk/src/osgPlugins/p3d/ReaderWriterP3D.cpp

    r13331 r13376  
    14201420        keyValue = itr->second; 
    14211421    } 
    1422     if (key.find("0x",0,2)!=std::string::npos) 
     1422    else if (key.find("0x",0,2)!=std::string::npos) 
    14231423    { 
    14241424        std::istringstream iss(key); 
     
    14391439    else 
    14401440    { 
    1441         OSG_NOTICE<<"Warning: invalid key used in <key>"<<key<<"</key>, ignoring tag."<<std::endl; 
     1441        OSG_NOTICE<<"Warning: invalid key used in <key>"<<key<<"</key>, ignoring tag. key=["<<key<<"]"<<std::endl; 
    14421442        return false; 
    14431443    }