Finish article about Mesa3D LLVM pipe to get modern OpenGL on a VM

articles/2019-06-12-opengl-kvm-mesa3d.md

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+---
+title: OpenGL in a virtual machine
+date: 2019-06-12 18:30:00
+---
+
+As I prefer to work on a Linux computer for programming, at work I have to
+use a virtual machine to execute the product and test in a real environment
+using different Windows versions.
+
+The problem encountered is that the emulated graphics card, even with full
+drivers in my KVM setup is only providing an OpenGL 1.1 version, something
+so old that some of the functionalities of our application are not working
+and display black boxes instead.
+
+After trying to install additional drivers or setup a more complete emulation,
+a newer emulated card or other complex steps, I found a simpler way : Using
+a Mesa3D driver with the llvmpipe that will emulate the lastest OpenGL features
+using what is available on the emulated machine. The result will not be fast
+enough for a 3D game for example, but every feature will become available.
+
+You can download an already compiled distribution of the Mesa3D sources at
+https://github.com/pal1000/mesa-dist-win/releases. By default, I download
+the msvc version as I usually have everything needed. Once downloaded, simply
+extract the archive in your download or Desktop folder.
+
+I usually install the library System-Wide, as a replacement to the Microsoft
+OpenGL software renderer that only support the very old OpenGL 1.1 version.
+
+![Install](install.png "Install")
+
+Select the first option to install the LLVM pipe System-Wide so that any
+application needing OpenGL will use the Mesa3D implementation instead of the
+Microsoft renderer without any further configuration needed.
+
+Once installed System-Wide, you can simply restart your application and
+check that the available OpenGL version has been bumped to a default 3.1
+version. This default version can be overridden by setting the `MESA_GL_VERSION_OVERRIDE`
+environment variable. For example, if you want to get OpenGL 4.6, you can
+create a `MyApplication.cmd` that will launch the executable :
+
+```
+@set MESA_GL_VERSION_OVERRIDE=4.6COMPAT
+@MyApplication.exe
+```
+
+It is important to note that profiles higher than the default can be incomplete and
+are not certified as a full implementation. If your application only uses
+extensions that are implemented, this will work but YMMV.