Off screen rendering on a linux virtual machine

Question

I'm currently working on a Linux virtual machine (Ubuntu 16-04 LTS) that has no GPU (because the cluster it runs on has no GPU).

I'm using the following simple C++ code to generate a thumbnail for a .PLY 3D model without opening a window and rendering everything off screen:

void produceThumbnail(const char* input, const char* output)
{
    viz::Mesh mesh = viz::Mesh::load(input);
    viz::WMesh wMesh(mesh);
    viz::Viz3d window("bunny");
    window.showWidget("bunny", wMesh);
    window.setBackgroundColor(viz::Color::azure());
    window.setOffScreenRendering();
    window.spinOnce();
    Mat3b img = window.getScreenshot();
    imwrite(output, img);
}

Using OpenCV 3.1.0 and VTK 6.3.0 everything works fine on Windows but on Linux i get a different behavior.

While debugging it, when spinOnce() is reached a window opens up anyway, even if i called setOffScreenRendering(), and in the console i get this error:

libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast

Despite the errors and the strange behavior the thumbnails are correctly produced and saved.

The real problem is that when I try execute this function when an X server is not available (e.g. NOT a remote desktop connection, an SSH console or something similar) i get the following error:

ERROR: In /home/administrator/libs/VTK-6.3.0/Rendering/OpenGL/vtkXOpenGlRenderWindow.cxx, line 1475
vtkXOpenGLRenderWindow (0x1ae93e0): bad X server connection. DISPLAY=Aborted

and the executable crashes (obviously, because there is no X server available... )

Looking online I have found many questions regarding wrong GPU-hardware/GPU-drivers configuration but nothing quite like my own case.

Running glxgears i get this:

libGL: OpenDriver: trying /usr/lib/x86_64-linux-gnu/dri/tls/swrast_dri.so
libGL: OpenDriver: trying /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
28843 frames in 5.0 seconds = 5766.824 FPS
28840 frames in 5.0 seconds = 5766.716 FPS
...

And running glxinfo i get this:

name of display: :10.0
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
display: :10  screen: 0
direct rendering: No (If you want to find out why, try setting LIBGL_DEBUG=verbose)
server glx vendor string: SGI
server glx version string: 1.2
server glx extensions:
    GLX_EXT_import_context, GLX_EXT_visual_info, GLX_EXT_visual_rating
client glx vendor string: Mesa Project and SGI
client glx version string: 1.4
client glx extensions:
    GLX_ARB_create_context, GLX_ARB_create_context_profile, 
    GLX_ARB_create_context_robustness, GLX_ARB_fbconfig_float, 
    GLX_ARB_framebuffer_sRGB, GLX_ARB_get_proc_address, GLX_ARB_multisample, 
    GLX_EXT_buffer_age, GLX_EXT_create_context_es2_profile, 
    GLX_EXT_create_context_es_profile, GLX_EXT_fbconfig_packed_float, 
    GLX_EXT_framebuffer_sRGB, GLX_EXT_import_context, 
    GLX_EXT_texture_from_pixmap, GLX_EXT_visual_info, GLX_EXT_visual_rating, 
    GLX_INTEL_swap_event, GLX_MESA_copy_sub_buffer, 
    GLX_MESA_multithread_makecurrent, GLX_MESA_query_renderer, 
    GLX_MESA_swap_control, GLX_OML_swap_method, GLX_OML_sync_control, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGIX_visual_select_group, GLX_SGI_make_current_read, 
    GLX_SGI_swap_control, GLX_SGI_video_sync
GLX version: 1.2
GLX extensions:
    GLX_ARB_get_proc_address, GLX_EXT_import_context, GLX_EXT_visual_info, 
    GLX_EXT_visual_rating, GLX_MESA_multithread_makecurrent
OpenGL vendor string: Mesa project: www.mesa3d.org
OpenGL renderer string: Mesa GLX Indirect
OpenGL version string: 1.3 Mesa 4.0.4
OpenGL extensions:
    GL_ARB_imaging, GL_ARB_multitexture, GL_ARB_texture_border_clamp, 
    GL_ARB_texture_cube_map, GL_ARB_texture_env_add, 
    GL_ARB_texture_env_combine, GL_ARB_texture_env_dot3, 
    GL_ARB_transpose_matrix, GL_EXT_abgr, GL_EXT_blend_color, 
    GL_EXT_blend_minmax, GL_EXT_blend_subtract, GL_EXT_draw_range_elements, 
    GL_EXT_multi_draw_arrays, GL_EXT_texture_env_add, 
    GL_EXT_texture_env_combine, GL_EXT_texture_env_dot3, 
    GL_EXT_texture_lod_bias, GL_SGIS_texture_border_clamp, 
    GL_SUN_multi_draw_arrays

I get that there must be something wrong with my driver configuration but i'm not really into these things (Linux configuration + 3D graphics + software rendering + etc) so i don't know what can i do to fix this.

Any suggestion about how can i solve this issue? (Or about doing the same thing in different way)

datenwolf datenwolf · Accepted Answer · 2016-06-23T13:29:51

The OpenGL implementation you're using expects an X server for it to provide drawables to draw into. For purely headless operation without an X server and without a GPU you should look into OSMesa: http://www.mesa3d.org/osmesa.html

Off screen rendering on a linux virtual machine

1 Answers