[vtkusers] Combined on-screen and off-screen possible with VTK-7.0.0 on linux/X?

Elvis Stansvik elvis.stansvik at orexplore.com
Fri Oct 28 09:18:44 EDT 2016 

Sorry for sort of necro-posting to this old thread, but I'm also
interested in if on- and off-screen rendering is possible with the
same build of VTK 7.x (using OpenGL2 backend in my case)? Or will I
need separate builds of VTK for this purpose? (and if so, if there are
plans to fix that).

Thanks in advance,
Elvis

2016-02-08 10:52 GMT+01:00 Michael Bachmann <Michael.Bachmann at synopsys.com>:
> Hello list!
> Hello Sophonet!
>
> First of all:
> => Thank you Sophonet for investigating this issue and for describing the patch to "VTKROOT/CMake/vtkOpenGL.cmake".
>      I applied your patch and it also re-enables offscreen rendering on a headless machine (were no X DISPLAY is available).
>
> Actually I really wonder why there are only a few posts about this issue.
> For the application I'm working on the ability of VTK7 to perform On-Screen and Off-Screen rendering with a single build of VTK is an absolute must-have! (Just like it was in VTK5 and VTK6)
>
> Please take the suggestion of Sophonet into account and re-enable it at least for the OpenGL rendering backend.
> Making this available for the OpenGL2 backend should also be considered.
>
> Building the software twice, e.g. like it is done for paraview (non-headless) and the paraview server (headless) is not an option for everyone.
> Actually is quite a big burden which has been silently put on the shoulders of VTK users.
>
> So please: Provide the facilities to perform On-Screen and Off-Screen rendering with a single build of VTK using OSMesa and X on Linux again!
>
> Best regards,
> Michael
>
>
>
> Date: Thu, 21 Jan 2016 14:54:46 +0100
> From: Sophonet <vtk12af6bc42 at kant.sophonet.de>
> To: vtkusers at vtk.org
> Subject: Re: [vtkusers] Combined on-screen and off-screen possible
>         with VTK-7.0.0 on linux/X?
> Message-ID: <ac1f14a73f567e2e8e5916a5c942dc04 at srv19.sysproserver.de>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> As one further follow-up of my two earlier e-mails, I have partly answered the question myself... remember, my question is related to the OpenGL (not OpenGL2) rendering backend.
>
> Two observations:
>
> 1. It seems that the current CMake flag VTK_OPENGL_HAS_OSMESA is useless, since it does not set anything relevant (see my e-mail below) 2. It seems that combined on-screen / off-screen rendering is possible (on Mesa 9.2.3 using the OpenGL rendering backend):
>
>     As a quick hack, I have changed VTKROOT/CMake/vtkOpenGL.cmake such that
>
>     * VTK_USE_OSMESA = True (triggers find_package OSMesa)
>     * VTK_USE_X = True (triggers find_package OpenGL)
>
>     ...and (at the bottom) vtk_module_link_libraries links to *both*, ${OSMESA_LIBRARY} and ${OPENGL_LIBRARIES}.
>
> After this hack, I can successfully launch interactive (glx-)renderwindows as well as set (occasionally) set SetOffscreenRenderingOn().
>
> Therefore, my suggestion would be to
>
> - remove VTK_OPENGL_HAS_OSMESA
> - change the vtkOpenGL.cmake such that VTK_USE_OSMESA is exposed as an advanced option and is not exclusive w.r.t. VTK_USE_X, but may be set at the same time.
>
> Any comments?
>
> Thanks,
>
>         Sophonet
>
>
> Am 2016-01-19 11:06, schrieb Sophonet:
>> As a follow-up, I have done some more investigations myself and am
>> still lost:
>>
>> According to http://www.vtk.org/Wiki/VTK/OSMesa_Support, it seems that
>> the legacy OSMesa library on linux systems is not needed anymore, but
>> that software renderers (such as gallium llvm) can provide off-screen
>> rendering themselves. Correct?
>>
>> When looking at VTKROOT/CMake/vtkOpenGL.cmake, it appears (not
>> perfectly sure though) that in this case VTK_OPENGL_HAS_OSMESA needs
>> to be turned on, since this flag sets VTK_CAN_DO_OFFSCREEN to 1.
>> However, it seems to me that VTK_CAN_DO_OFFSCREEN is not used anywhere
>> else (did a thorough "grep" on that keyword in the source tree).
>>
>> It seems that Marcus (Hanwell) was responsible for many of these
>> changes in CMake - Marcus, can you help?
>>
>> What I would like to do is (see my first e-mail below) to
>> simultaneously use interactive rendering and (occasionally) off-screen
>> rendering (for generating static images), which was possible on Linux
>> in earlier versions of VTK (e.g. 5.10), but is not possible anymore.
>>
>> Thanks,
>>
>>        Sophonet
>>
>>
>> Am 2016-01-15 12:44, schrieb Sophonet:
>>> Dear list,
>>>
>>> in my application, I would like to display a vtkRenderWindow for user
>>> interaction, but I also would like to use off-screen functionality
>>> simultaneously to render pre-defined views / snapshots that are shown
>>> as static images, like "thumbnails" for different datasets.
>>>
>>> This was possible in VTK 5.10 on linux (by creating a dedicated
>>> vtkRenderWindow per thumbnail, setting OffScreenRenderingOn,
>>> rendering and capturing the resulting image with a vtkWindowToImageFilter).
>>>
>>> In VTK-7.0.0.rc1, using the OpenGL rendering backend on Mesa 9.2.3, I
>>> now get a segfault with the following backtrace:
>>>
>>> (gdb) bt
>>> #0  0x00007fffd045db90 in xcb_glx_get_string_string_length ()
>>>    from /usr/lib64/libxcb-glx.so.0
>>> #1  0x00007fffd0cce605 in ?? () from /usr/lib64/libGL.so.1
>>> #2  0x00007fffd0ccc2b6 in ?? () from /usr/lib64/libGL.so.1
>>> #3  0x00007fffd14cd086 in
>>> vtkOpenGLExtensionManager::ReadOpenGLExtensions() ()
>>>    from
>>> /import/QUINTA/non-public/software/linux-install/quinta_gcc_debug/lib
>>> /libvtkRenderingOpenGL-7.0.so.1
>>> #4  0x00007fffd14cbd50 in vtkOpenGLExtensionManager::Update() ()
>>>    from
>>> /import/QUINTA/non-public/software/linux-install/quinta_gcc_debug/lib
>>> /libvtkRenderingOpenGL-7.0.so.1
>>> #5  0x00007fffd14cafd7 in
>>> vtkOpenGLExtensionManager::ExtensionSupported(char const*) ()
>>>    from
>>> /import/QUINTA/non-public/software/linux-install/quinta_gcc_debug/lib
>>> /libvtkRenderingOpenGL-7.0.so.1
>>> #6  0x00007fffd14ec8ea in vtkOpenGLRenderWindow::OpenGLInitContext()
>>> ()
>>>    from
>>> /import/QUINTA/non-public/software/linux-install/quinta_gcc_debug/lib
>>> /libvtkRenderingOpenGL-7.0.so.1
>>> #7  0x00007fffd14eae6d in vtkOpenGLRenderWindow::OpenGLInit() ()
>>>    from
>>> /import/QUINTA/non-public/software/linux-install/quinta_gcc_debug/lib
>>> /libvtkRenderingOpenGL-7.0.so.1
>>> #8  0x00007fffd1576932 in
>>> vtkXOpenGLRenderWindow::CreateOffScreenWindow(int, int) ()
>>>
>>> Besides a remark that probably there could be better error handling
>>> than just letting the app crash without an exception being thrown, I
>>> would like to know if joint on-screen rendering and off-screen
>>> rendering is still possible somehow with VTK-7.0.0.
>>>
>>> I have made two approaches when configuring via CMake: (i) Setting
>>> VTK_OPENGL_HAS_OSMESA=True (no effect, I think I remember that in
>>> earlier versions, this allowed OSMESA_INCLUDE_DIR etc. to be set;
>>> this is not the case anymore, so does this flag still do something?
>>> Note that for VTK 5.10 as mentioned above I did not have to set this
>>> explicitly), (ii) Setting USE_OFFSXCREEN_EGL=True - resulting in an
>>> error that this could not be combined with VTK_USE_X.
>>>
>>> On Windows, combining on-screen and off-screen rendering as described
>>> in the second paragraph is possible.
>>>
>>> Any suggestions would be welcome, the Wiki page I have found on this
>>> topic is not fully understandable to me
>>> (http://www.vtk.org/Wiki/VTK/OSMesa_Support; does this mean that I
>>> have to switch on VTK_OPENGL_HAS_OSMESA or not?...)
>>>
>>> Thanks,
>>>
>>>       sophonet
>>>
>>>
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>> _______________________________________________
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>> Visit other Kitware open-source projects at
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>> Please keep messages on-topic and check the VTK FAQ at:
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>
>
> _______________________________________________
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>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
>
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