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Timestamp:
09/04/15 17:35:24 (16 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/applications/present3D/deprecated/PointsEventHandler.cpp

    r13720 r13890  
    1 /* -*-c++-*- Present3D - Copyright (C) 1999-2006 Robert Osfield  
     1/* -*-c++-*- Present3D - Copyright (C) 1999-2006 Robert Osfield 
    22 * 
    3  * This software is open source and may be redistributed and/or modified under   
     3 * This software is open source and may be redistributed and/or modified under 
    44 * the terms of the GNU General Public License (GPL) version 2.0. 
    55 * The full license is in LICENSE.txt file included with this distribution,. 
    6  *  
     6 * 
    77 * This software is distributed in the hope that it will be useful, 
    88 * but WITHOUT ANY WARRANTY; without even the implied warranty of 
    9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the  
     9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
    1010 * include LICENSE.txt for more details. 
    1111*/ 
     
    5555} 
    5656 
    57 void PointsEventHandler::accept(osgGA::GUIEventHandlerVisitor& v) 
    58 { 
    59     v.visit(*this); 
    60 } 
    61  
    6257void PointsEventHandler::getUsage(osg::ApplicationUsage& usage) const 
    6358{