It's uncommon, but every now and then a thread pops up in the Mapping Help & Discussion subforum where this is included in the compile log:
So what's going on here? Simply put, VVIS and VRAD (what makes your optimization and lighting) depend on the Microsoft Visual C++ redistribute packages. Without it installed on your computer, these processes won't be able to run. This usually shows up on your computer as you install and run games, as some require it, but it doesn't come preinstalled on Windows! Additionally, most users seem to have success with the X86 version, so give that version a spin.
https://www.microsoft.com/en-us/download/details.aspx?id=52685
So what's going on here? Simply put, VVIS and VRAD (what makes your optimization and lighting) depend on the Microsoft Visual C++ redistribute packages. Without it installed on your computer, these processes won't be able to run. This usually shows up on your computer as you install and run games, as some require it, but it doesn't come preinstalled on Windows! Additionally, most users seem to have success with the X86 version, so give that version a spin.
https://www.microsoft.com/en-us/download/details.aspx?id=52685
