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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/src/osg/ImageUtils.cpp

    r13204 r13205  
    616616 
    617617 
    618 struct ModulateAlphaByColourOperator 
    619 { 
    620     ModulateAlphaByColourOperator(const osg::Vec4& colour):_colour(colour) { _lum = _colour.length(); } 
     618 
     619struct ModulateAlphaByColorOperator 
     620{ 
     621    ModulateAlphaByColorOperator(const osg::Vec4& colour):_colour(colour) { _lum = _colour.length(); } 
    621622 
    622623    osg::Vec4 _colour; 
     
    651652            return image; 
    652653        } 
    653         case (MODULATE_ALPHA_BY_COLOUR): 
     654        case (MODULATE_ALPHA_BY_COLOR): 
    654655        { 
    655656            OSG_NOTICE<<"doing conversion MODULATE_ALPHA_BY_COLOUR"<<std::endl; 
    656             osg::modifyImage(image, ModulateAlphaByColourOperator(colour)); 
     657            osg::modifyImage(image, ModulateAlphaByColorOperator(colour)); 
    657658            return image; 
    658659        }