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Timestamp:
09/04/15 17:35:24 (25 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/include/osgDB/ReadFile

    r13041 r13172  
    4444inline osg::Object* readObjectFile(const std::string& filename) 
    4545{ 
    46     return readObjectFile(filename,Registry::instance()->getOptions()); 
    47 } 
     46    return readObjectFile(filename, Registry::instance()->getOptions()); 
     47} 
     48 
     49template<typename T> 
     50inline T* readFile(const std::string& filename, const Options* options) 
     51{ 
     52    osg::ref_ptr<osg::Object> object = readObjectFile(filename, options); 
     53    osg::ref_ptr<T> t = dynamic_cast<T*>(object.get()); 
     54    object = 0;     
     55    return t.release(); 
     56} 
     57 
     58template<typename T> 
     59inline T* readFile(const std::string& filename) 
     60{ 
     61    return readFile<T>(filename, Registry::instance()->getOptions()); 
     62} 
     63 
    4864 
    4965/** Read an osg::Image from file.