1. Lumion 6.5 and newer:
Lumion 6.5 and newer requires Windows 10 or Windows 11.
To see which version of Windows 10 or Windows 11 you currently have installed, click on the Windows button and select Settings -> System -> About, to see the version number.
2. Lumion 6.3 and older:
If you're using Lumion 6.3 or older and need more than 4 GB of memory for your Projects, we recommend that you run Lumion on Windows 7 (64-bit with at least SP1).
The reason is that Windows 8 and 10 do not allow older DirectX 9 applications (such as Lumion 6.3 and older) to use more than 4 GB graphics card memory for a given application - and no system memory either. On Windows 7, graphics card memory and system memory are not limited by the 4 GB cap when running older DirectX 9 applications such as Lumion 1.0-6.3.
Lumion 6.5 and newer are not affected by this cap and can use more than 4 GB memory on Windows 7, 8 and 10.