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    Hi burlen,<br>
    <br>
    thanks for the valuable insights. The glXGetProcAddress* functions
    were present, in both the nvidia version of libGL.so:<br>
    <tt> $ nm -CD /usr/lib/nvidia-310/libGL.so | grep glXGetProcAdd</tt><tt><br>
    </tt><tt>000000000007d360 T glXGetProcAddress</tt><tt><br>
    </tt><tt>000000000007d470 T glXGetProcAddressARB</tt><tt><br>
    </tt><br>
    as well as the original mesa implementation (that I renamed to get
    it out of the way):<br>
    <tt>$ nm -CD /usr/lib/x86_64-linux-gnu/mesa/libGL.so.1.2.0.renamed |
      grep glXGetProcAdd</tt><tt><br>
    </tt><tt>00000000000190e0 T glXGetProcAddress</tt><tt><br>
    </tt><tt>00000000000190e0 T glXGetProcAddressARB</tt><tt><br>
    </tt><br>
    But the cmake didn't seem to find them:<br>
    <tt>$ grep  -i GLX ./CMakeCache.txt</tt><tt><br>
      &lt;...&gt;</tt><tt><br>
    </tt><tt><b>//Have function glXGetProcAddress</b></tt><tt><b><br>
      </b></tt><tt><b>VTK_USE_GLX_GET_PROC_ADDRESS:INTERNAL=</b></tt><tt><b><br>
      </b></tt><tt><b>//Have function glXGetProcAddressARB</b></tt><tt><b><br>
      </b></tt><tt><b>VTK_USE_GLX_GET_PROC_ADDRESS_ARB:INTERNAL=</b></tt><b><br>
    </b><br>
    I had done only 'make clean' when I recompiled VTK with new nvidia
    drivers. After erasing the cmake cache and recompiling against
    nvidia libGL.so I am a happy camper, all the extensions are
    reported, all the regression tests pass and my volume renders
    smoothly. <br>
    Thank you tons!!! :)<br>
    Miro<br>
    <br>
    <br>
    <br>
    <div class="moz-cite-prefix">On 09/11/2013 05:03 PM, burlen wrote:<br>
    </div>
    <blockquote cite="mid:523104BF.2020106@gmail.com" type="cite">
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      <div class="moz-cite-prefix">Hi Miro<br>
        <br>
        <blockquote type="cite"><tt>203 - LoadOpenGLExtension (Failed)</tt><tt><br>
          </tt></blockquote>
        keep it simple. forget about the GPURayCast until this test
        passes.<br>
        <br>
        <blockquote type="cite"><b><tt>#define VTK_NO_EXTENSION_LOADING</tt></b><tt><br>
          </tt></blockquote>
        that happens if neither glXGetProcAddressARB nor
        glXGetProcAddress is found. I think this is your problem. I
        could verify these are around as follows:<br>
        <blockquote>$ grep glXGetProcAddress /usr/include/GL/ -rIn<br>
          $ nm -CD /usr/lib/x86_64-linux-gnu/libGL.so | grep
          glXGetProcAdd<br>
        </blockquote>
        and verify that VTK found them too:<br>
        <blockquote>$grep GLX ./CMakeCache.txt<br>
        </blockquote>
        <br>
        <blockquote type="cite">after I installed nvidia propriatory
          driver, I got another libGL.so in /usr/lib/nvidia-310/libGL.so
          so I re-configured vtk</blockquote>
        did you rm -rf your build just to make sure that there's no bad
        values in your cmake cache? might be worth  a try if you hadn't.<br>
        <br>
        Burlen<br>
        <br>
        <br>
        On 09/11/2013 03:36 PM, Miro Drahos wrote:<br>
      </div>
      <blockquote cite="mid:5230F065.2070006@robodoc.com" type="cite">
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        Thanks burlen and Julien.<br>
        <br>
        I did call Render() to initialize the GL context. Created a new
        plain vtkRenderWindow too (in my application I use QVTKWidget):<br>
        <tt>  cout &lt;&lt; " DEBUG standalone renwin" &lt;&lt; endl;</tt><br>
           <tt>vtkRenderWindow * rw = vtkRenderWindow::New();</tt><tt><br>
        </tt><tt>  rw-&gt;SetSize(512, 512);</tt><tt><br>
        </tt><tt>  rw-&gt;Render();</tt><tt><br>
        </tt><tt>  </tt><tt><br>
        </tt><tt>  VTK_CREATE(vtkRenderer, ren);</tt><tt><br>
        </tt><tt>  ren-&gt;AddViewProp(this-&gt;m_volume);</tt><tt><br>
        </tt><tt>  rw-&gt;AddRenderer(ren);</tt><tt><br>
        </tt><tt><br>
        </tt><tt>  vtkOpenGLExtensionManager
          *extensions=vtkOpenGLExtensionManager::New();</tt><tt><br>
        </tt><tt>  extensions-&gt;SetRenderWindow(rw);</tt><tt><br>
        </tt><tt>  extensions-&gt;Update();</tt><tt><br>
        </tt><tt><br>
        </tt><tt>  cout &lt;&lt; " SUPPORTS 1.3? " &lt;&lt;
          extensions-&gt;ExtensionSupported("GL_VERSION_1_3") &lt;&lt;
          endl;</tt><tt><br>
        </tt><tt>  cout &lt;&lt; "====================== exts:
          ==================== " &lt;&lt;</tt><tt><br>
        </tt><tt>    extensions-&gt;GetExtensionsString() &lt;&lt; </tt><tt><br>
        </tt><tt>    "==================================================
          " &lt;&lt; endl;</tt><tt><br>
        </tt><tt>  rw-&gt;Render();</tt><tt><br>
        </tt><tt>  cout &lt;&lt; " DEBUG standalone renwin done"
          &lt;&lt; endl;  </tt><tt><br>
        </tt><br>
        But the terminal output shows empty string:<br>
        <tt> DEBUG standalone renwin</tt><tt><br>
        </tt><tt> SUPPORTS 1.3? 0</tt><tt><br>
        </tt><tt>====================== exts: ====================
          ================================================== </tt><tt><br>
        </tt><tt>ERROR: In
          /home/miro/BUILDS/VTK5.10.1/VolumeRendering/vtkOpenGLVolumeTextureMapper3D.cxx,


          line 100</tt><tt><br>
        </tt><tt>vtkOpenGLVolumeTextureMapper3D (0xba0c9c0): required
          extensions not supported</tt><tt><br>
        </tt><tt><br>
        </tt><tt> DEBUG standalone renwin done</tt><tt><br>
        </tt><br>
        Julien's hint got me to dig deeper into why I am getting the
        empty GetExtensionsString().<br>
        <br>
        Looking at the sources, the reason why it returns an empty
        string is because of this #define:<br>
        VTK_NO_EXTENSION_LOADING<br>
        which causes vtkOpenGLExtensionManager::ReadOpenGLExtensions()
        to set the extensions to empty string<br>
        This #define gets into play from #include'd
        vtkOpenGLExtensionManagerConfigure.h which contains only the
        following:<br>
        <tt><br>
        </tt><tt>/* #undef VTK_USE_WGL_GET_PROC_ADDRESS */</tt><tt><br>
        </tt><tt>/* #undef VTK_USE_APPLE_LOADER */</tt><tt><br>
        </tt><tt>/* #undef VTK_USE_GLX_GET_PROC_ADDRESS */</tt><tt><br>
        </tt><tt>/* #undef VTK_USE_GLX_GET_PROC_ADDRESS_ARB */</tt><tt><br>
        </tt><tt>/* #undef VTK_USE_VTK_DYNAMIC_LOADER */</tt><tt><br>
        </tt><b><tt>#define VTK_NO_EXTENSION_LOADING</tt></b><tt><br>
        </tt><tt><br>
        </tt><tt>/* #undef VTK_DEFINE_GLX_GET_PROC_ADDRESS_PROTOTYPE */</tt><tt><br>
        </tt><tt><br>
        </tt><tt>// If using vtkDynamicLoader, we need to know where the
          libraries are.</tt><tt><br>
        </tt><tt>#define OPENGL_LIBRARIES
"/usr/lib/x86_64-linux-gnu/libGLU.so;/usr/lib/x86_64-linux-gnu/libGL.so;/usr/lib/x86_64-linux-gnu/libSM.so;/usr/lib/x86_64-linux-gnu/libICE.so;/usr/lib/x86_64-linux-gnu/libX11.so;/usr/lib/x86_64-linux-gnu/libXext.so"</tt><tt><br>
        </tt><br>
        This #define must have gotten there when configuring the VTK
        build. I tried to search CMakeLists.txt for
        VTK_NO_EXTENSION_LOADING and it appers in this section (which I
        admit I have no clue about):<br>
         <tt> IF(VTK_USE_X)</tt><tt><br>
        </tt><tt>      CHECK_FUNCTION_EXISTS(glXGetProcAddressARB
          VTK_USE_GLX_GET_PROC_ADDRESS_ARB)</tt><tt><br>
        </tt><tt>      IF (VTK_USE_GLX_GET_PROC_ADDRESS_ARB)</tt><tt><br>
        </tt><tt>        IF (NOT
          "${VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS_INCLUDES}"
          STREQUAL "${OPENGL_INCLUDE_DIR}")</tt><tt><br>
        </tt><tt>          # The OpenGL includes changed.  Retest
          glXGetProcAddressARB prototype.</tt><tt><br>
        </tt><tt>         
          SET(VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS_TESTED 0)</tt><tt><br>
        </tt><tt>        ENDIF (NOT
          "${VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS_INCLUDES}"
          STREQUAL "${OPENGL_INCLUDE_DIR}")</tt><tt><br>
        </tt><tt>        IF (NOT
          VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS_TESTED)</tt><tt><br>
        </tt><tt>          MESSAGE(STATUS "Looking for
          glXGetProcAddressARB in GL/glx.h")</tt><tt><br>
        </tt><tt>         
          TRY_COMPILE(VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS</tt><tt><br>
        </tt><tt>            ${CMAKE_BINARY_DIR}</tt><tt><br>
        </tt><tt>           
          ${CMAKE_CURRENT_SOURCE_DIR}/CheckglXGetProcAddressARB.cxx</tt><tt><br>
        </tt><tt>            CMAKE_FLAGS
          "-DLINK_LIBRARIES:STRING=${CMAKE_REQUIRED_LIBRARIES}"</tt><tt><br>
        </tt><tt>           
          "-DINCLUDE_DIRECTORIES:STRING=${OPENGL_INCLUDE_DIR}"</tt><tt><br>
        </tt><tt>            OUTPUT_VARIABLE OUTPUT)</tt><tt><br>
        </tt><tt>          MESSAGE(STATUS "Looking for
          glXGetProcAddressARB in GL/glx.h -
          ${VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS}")</tt><tt><br>
        </tt><tt>          FILE(APPEND
          ${CMAKE_BINARY_DIR}/CMakeOutput.log</tt><tt><br>
        </tt><tt>            "Determining if glXGetProcAddressARB exists
          in GL/glx.h ${VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS}
          with the following output:\n"</tt><tt><br>
        </tt><tt>            "${OUTPUT}\n\n")</tt><tt><br>
        </tt><tt>         
          SET(VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS_TESTED 1</tt><tt><br>
        </tt><tt>            CACHE INTERNAL "Already set
          VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS")</tt><tt><br>
        </tt><tt>         
          SET(VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS_INCLUDES</tt><tt><br>
        </tt><tt>            "${OPENGL_INCLUDE_DIR}"</tt><tt><br>
        </tt><tt>            CACHE INTERNAL "OpenGL includes used to
          test glXGetProcAddressARB prototype.")</tt><tt><br>
        </tt><tt>        ENDIF (NOT
          VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS_TESTED)</tt><tt><br>
        </tt><tt>        IF (NOT
          VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS)</tt><tt><br>
        </tt><tt>          SET(VTK_DEFINE_GLX_GET_PROC_ADDRESS_PROTOTYPE
          1)</tt><tt><br>
        </tt><tt>        ENDIF (NOT
          VTK_GLX_GET_PROC_ADDRESS_ARB_PROTOTYPE_EXISTS)</tt><tt><br>
        </tt><tt>      ELSE (VTK_USE_GLX_GET_PROC_ADDRESS_ARB)</tt><tt><br>
        </tt><tt>        CHECK_FUNCTION_EXISTS(glXGetProcAddress
          VTK_USE_GLX_GET_PROC_ADDRESS)</tt><tt><br>
        </tt><tt>        IF (NOT VTK_USE_GLX_GET_PROC_ADDRESS)</tt><tt><br>
        </tt><tt>          #         SET(VTK_USE_VTK_DYNAMIC_LOADER 1)</tt><tt><br>
        </tt><tt>          MESSAGE(STATUS "Could not find extension
          loader.  Extensions disabled.")</tt><tt><br>
        </tt><b><tt>          SET(VTK_NO_EXTENSION_LOADING 1)</tt></b><tt><br>
        </tt><tt>        ENDIF (NOT VTK_USE_GLX_GET_PROC_ADDRESS)</tt><tt><br>
        </tt><tt>      ENDIF (VTK_USE_GLX_GET_PROC_ADDRESS_ARB)</tt><tt><br>
        </tt><tt>    ELSE(VTK_USE_X)</tt><tt><br>
        </tt><b><tt>      SET(VTK_NO_EXTENSION_LOADING 1)</tt></b><tt><br>
        </tt><tt>    ENDIF(VTK_USE_X)</tt><tt><br>
        </tt><br>
        When configuring VTK, the cmake option VTK_OPENGL_HAS_OSMESA was
        OFF, if it matters at all.<br>
        Some other openGL options in cmake config:<br>
        <tt> OPENGL_INCLUDE_DIR              
          /usr/include                                                                          


        </tt><tt><br>
        </tt><tt> OPENGL_gl_LIBRARY               
          /usr/lib/x86_64-linux-gnu/libGL.so                                                    


        </tt><tt><br>
        </tt><tt> OPENGL_glu_LIBRARY              
          /usr/lib/x86_64-linux-gnu/libGLU.so                                                   


        </tt><tt><br>
        </tt><tt> OPENGL_xmesa_INCLUDE_DIR        
          OPENGL_xmesa_INCLUDE_DIR-NOTFOUND     </tt><tt><br>
        </tt><br>
        Now after I installed nvidia propriatory driver, I got another
        libGL.so in /usr/lib/nvidia-310/libGL.so so I re-configured vtk
        with <br>
        <tt>  </tt><tt>OPENGL_gl_LIBRARY               
          /usr/lib/nvidia-310/libGL.so                                                    


        </tt><tt><br>
        </tt>instead and recompiled, but it didn't change things. The
        vtkOpenGLExtensionManagerConfigure.h still #defines
        VTK_NO_EXTENSION_LOADING.<br>
        <br>
        The tests (thanks burlen!) show the following:<br>
        <tt><br>
        </tt><tt>$ ctest -R LoadOpenGL --verbose | grep GL_</tt><tt><br>
        </tt><tt>203: GL_VENDOR: NVIDIA Corporation</tt><tt><br>
        </tt><tt>203: GL_VERSION: 4.3.0 NVIDIA 310.44</tt><tt><br>
        </tt><tt>203: GL_RENDERER: GeForce GT 520/PCIe/SSE2</tt><tt><br>
        </tt><tt>Errors while running CTest</tt><br>
        <br>
        The relevant failed line was this:<br>
        <tt>The following tests FAILED:</tt><tt><br>
        </tt><tt>    203 - LoadOpenGLExtension (Failed)</tt><tt><br>
        </tt><br>
        Then the Tests binary shows nvidia's libGL.so in use, as
        expected:<br>
        <tt>$ ldd bin/RenderingCxxTests | grep GL</tt><tt><br>
        </tt><tt>    libGL.so.1 =&gt; /usr/lib/nvidia-310/libGL.so.1
          (0x00007f75d8888000)</tt><tt><br>
        </tt><br>
        But most interestingly, <br>
        <tt>ctest -R GPURay </tt><br>
        all tests in this battery pass, only one segfaults:<br>
        <br>
        <tt> 8/17 Test #303: TestGPURayCastDataTypesMinIP
          .....................***Exception: SegFault  0.02 sec</tt><br>
        <br>
        That being said, I see the renderwindow flicker, but I don't see
        any content (e.g. sphere) rendered. I'd like to run the tests in
        interactive mode, but not sure how?<br>
        <br>
        I could build the latest vtk version from git and see whether I
        can replicate the issue there if you think it would make
        debugging easier.<br>
        <br>
        Some more info on my system: <br>
        Installed OpenGL-related packages:<br>
        <tt>$ sudo dpkg-query -l | egrep -i 'mesa|opengl'</tt><tt><br>
        </tt><tt>ii  compiz-core                                
          1:0.9.9~daily13.06.19~13.04-0ubuntu1       amd64        OpenGL
          window and compositing manager</tt><tt><br>
        </tt><tt>ii  compiz-plugins-default                     
          1:0.9.9~daily13.06.19~13.04-0ubuntu1       amd64        OpenGL
          window and compositing manager - default plugins</tt><tt><br>
        </tt><tt>ii  glew-utils                                 
          1.9.0.is.1.8.0-0ubuntu1                    amd64        OpenGL
          Extension Wrangler - utilities</tt><tt><br>
        </tt><tt>ii  libegl1-mesa:amd64                         
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the EGL API -- runtime</tt><tt><br>
        </tt><tt>ii  libegl1-mesa-dev                           
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the EGL API -- development files</tt><tt><br>
        </tt><tt>ii  libegl1-mesa-drivers:amd64                 
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the EGL API -- hardware drivers</tt><tt><br>
        </tt><tt>ii  libgl1-mesa-dev                            
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the OpenGL API -- GLX development files</tt><tt><br>
        </tt><tt>ii  libgl1-mesa-dri:amd64                      
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the OpenGL API -- DRI modules</tt><tt><br>
        </tt><tt>ii  libgl1-mesa-dri-dbg:amd64                  
          9.1.3-0ubuntu0.3                           amd64       
          Debugging symbols for the Mesa DRI modules</tt><tt><br>
        </tt><tt>ii  libgl1-mesa-glx:amd64                      
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the OpenGL API -- GLX runtime</tt><tt><br>
        </tt><tt>ii  libgl2ps0                                  
          1.3.6-1                                    amd64        Lib
          providing high quality vector output for OpenGL application</tt><tt><br>
        </tt><tt>ii  libglapi-mesa:amd64                        
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the GL API -- shared library</tt><tt><br>
        </tt><tt>ii  libgles2-mesa:amd64                        
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the OpenGL|ES 2.x API -- runtime</tt><tt><br>
        </tt><tt>ii  libglew1.8:amd64                           
          1.9.0.is.1.8.0-0ubuntu1                    amd64        OpenGL
          Extension Wrangler - runtime environment</tt><tt><br>
        </tt><tt>ii  libglewmx1.8:amd64                         
          1.9.0.is.1.8.0-0ubuntu1                    amd64        OpenGL
          Extension Wrangler (Multiple Rendering Contexts)</tt><tt><br>
        </tt><tt>ii  libglu1-mesa:amd64                         
          9.0.0-0ubuntu1                             amd64        Mesa
          OpenGL utility library (GLU)</tt><tt><br>
        </tt><tt>ii  libglu1-mesa-dev                           
          9.0.0-0ubuntu1                             amd64        Mesa
          OpenGL utility library -- development files</tt><tt><br>
        </tt><tt>ii  libopenvg1-mesa:amd64                      
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the OpenVG API -- runtime</tt><tt><br>
        </tt><tt>ii  libopenvg1-mesa-dev                        
          9.1.3-0ubuntu0.3                           amd64        free
          implementation of the OpenVG API -- development files</tt><tt><br>
        </tt><tt>ii  libqt4-opengl:amd64                        
          4:4.8.4+dfsg-0ubuntu9.2                    amd64        Qt 4
          OpenGL module</tt><tt><br>
        </tt><tt>ii  libreoffice-ogltrans                       
          1:4.0.2-0ubuntu1                           amd64       
          LibreOffice Impress extension for transitions using OpenGL</tt><tt><br>
        </tt><tt>ii  libtxc-dxtn-s2tc0:amd64                    
          0~git20121227-1                            amd64       
          Texture compression library for Mesa</tt><tt><br>
        </tt><tt>ii  mesa-common-dev                            
          9.1.3-0ubuntu0.3                           amd64       
          Developer documentation for Mesa</tt><tt><br>
        </tt><tt>ii  mesa-utils                                 
          8.0.1+git20110129+d8f7d6b-0ubuntu2         amd64       
          Miscellaneous Mesa GL utilities</tt><tt><br>
        </tt><tt>ii  x11proto-gl-dev                            
          1.4.16-1                                   all          X11
          OpenGL extension wire protocol</tt><tt><br>
        </tt><br>
        Thanks again!<br>
        Miro<br>
        <br>
        <br>
        <br>
        <br>
        <br>
        <div class="moz-cite-prefix">On 09/11/2013 03:08 PM, burlen
          wrote:<br>
        </div>
        <blockquote cite="mid:5230E9DE.40606@gmail.com" type="cite">
          <meta http-equiv="Content-Type" content="text/html;
            charset=windows-1252">
          <div class="moz-cite-prefix">also, did you call
            "renWin-&gt;Render()" once before using the extension
            manager? or class that uses the extension manager?<br>
            <br>
            On 09/11/2013 02:21 PM, burlen wrote:<br>
          </div>
          <blockquote cite="mid:5230DEEA.5080001@gmail.com" type="cite">
            <div class="moz-cite-prefix">in your vtk build dir, what
              does the output of <br>
              <blockquote>$ ctest -R LoadOpenGL --verbose | grep GL_<br>
              </blockquote>
              say? If it's not reporting the expected versions then you
              could verify which driver VTK using with:<br>
              <blockquote>$ ldd bin/vtkRenderingVolumeCxxTests | grep GL<br>
              </blockquote>
              you may try this also on your app to verify. Do VTK's
              tests have the same issue?<br>
              <blockquote>$ ctest -R GPURay --verbose<br>
              </blockquote>
              if none of this helps, would you be willing to work with
              the development version of VTK? it will be easier to find
              and fix the bug.<br>
              <br>
              Burlen<br>
              <br>
              On 09/10/2013 07:21 PM, Miro Drahos wrote:<br>
            </div>
            <blockquote cite="mid:522FD390.4000302@robodoc.com"
              type="cite"> Hi all,<br>
              I am having an issue with volume mappers and hope someone
              can provide some constructive feedback.<br>
              When trying to use vtkGPUVolumeRayCastMapper rendering
              fails with the message:<br>
              <tt>ERROR: In
                /home/miro/BUILDS/VTK5.10.1/VolumeRendering/vtkOpenGLGPUVolumeRayCastMapper.cxx,





                line 4011</tt><tt><br>
              </tt><tt>vtkOpenGLGPUVolumeRayCastMapper (0x12e15ce0):
                Rendering failed because the following OpenGL extensions
                are required but not supported:  OpenGL 1.3 is required
                but not supported</tt><br>
              <br>
              If I run <br>
              <tt>glGetString(GL_VERSION)</tt><br>
              I get the correct output string:<br>
              <tt>4.3.0 NVIDIA 310.44</tt><br>
              <br>
              and yet the
              vtkOpenGLExtensionManager::ExtensionSupported("GL_VERSION_1_3")
              somehow returns 0.<br>
              <br>
              I am using vtk 5.10, my graphics card is NVIDIA GT520,
              using NVIDIA propriatory driver 310.44 on Linux Mint 15
              (same thing with open-source nouveau driver).<br>
              Some terminal output that may be relevant:<br>
              <tt><br>
              </tt><tt>$ glewinfo   | grep GL_VER</tt><tt><br>
              </tt><tt>GL_VERSION_1_1:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_1_2:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_1_2_1:                                             





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_1_3:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_1_4:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_1_5:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_2_0:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_2_1:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_3_0:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_3_1:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_3_2:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_3_3:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_4_0:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_4_1:                                               





                OK </tt><tt><br>
              </tt><tt>GL_VERSION_4_2:                                               





                OK </tt><tt><br>
              </tt><tt><br>
              </tt><tt>$ inxi -Gx</tt><tt><br>
              </tt><tt>Graphics:  Card: NVIDIA GF119 [GeForce GT 520]
                bus-ID: 01:00.0 </tt><tt><br>
              </tt><tt>           X.Org: 1.13.3 drivers: nvidia
                (unloaded: fbdev,vesa,nouveau) Resolution: <a
                  moz-do-not-send="true"
                  class="moz-txt-link-abbreviated"
                  href="mailto:1920x1080@60.0hz">1920x1080@60.0hz</a>, <a
                  moz-do-not-send="true"
                  class="moz-txt-link-abbreviated"
                  href="mailto:1920x1080@60.0hz">1920x1080@60.0hz</a> </tt><tt><br>
              </tt><tt>           GLX Renderer: GeForce GT 520/PCIe/SSE2
                GLX Version: 4.3.0 NVIDIA 310.44 Direct Rendering: Yes</tt><tt><br>
              </tt><br>
              <br>
              More puzzling yet it gets when I try to use
              vtkVolumeMapperTexture3D, I get <br>
              <tt>ERROR: In
                /home/miro/BUILDS/VTK5.10.1/VolumeRendering/vtkOpenGLGPUVolumeRayCastMapper.cxx,





                line 4011</tt><tt><br>
              </tt><tt>vtkOpenGLGPUVolumeRayCastMapper (0x12e15ce0):
                Rendering failed because the following OpenGL extensions
                are required but not supported: </tt><br>
              <br>
              With no list of problem extensions...<br>
              <br>
              Thank you very much for any input on this!<br>
              <br>
              <div class="moz-signature">
                <div style="font-size:95%; width:13.5em;text-align:left;
                  padding-left:1em; .moz-signature { display: none; }">
                  <hr style="width:11em; border-top:3px double #aaa;
                    width:155%; margin-left:-0.5em;"> Miroslav Drahoš<br>
                  <div style="font-size:75%"> software engineer<br>
                    <a moz-do-not-send="true"
                      href="http://www.robodoc.com"><img
                        src="cid:part3.02020808.07050009@robodoc.com"
                        height="31px" width="128px"></a><br>
                    <b>Curexo Technology Corporation</b><br>
                    47320 Mission Falls Ct<br>
                    Fremont CA, 94539<br>
                    Tel: (510) 249-2300 x2372<br>
                    Fax: (510) 249-2396<br>
                    <a moz-do-not-send="true"
                      href="http://www.robodoc.com">www.robodoc.com</a><br>
                    <br>
                  </div>
                </div>
              </div>
              <br>
              <fieldset class="mimeAttachmentHeader"></fieldset>
              <br>
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</pre>
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