Should Direct3D 11 be used when available?
Using DX11 enables more modern graphics features, like Compute Shaders,
tessellation shaders and other shader model 4.0-5.0 features.
This flag is specific to Windows Editor, Standalone and Web Player builds.
When set to true, Unity will try to use the Direct3D 11 graphics API (which works on Windows Vista
or later OS, and DX10+ level GPU). If that is not available (e.g. DX9 level GPU or Windows XP),
Direct3D 9 will be used instead.
When set to false, Direct3D 9 API will be used.