How does Looking Glass work?

Please see the following video that covers this:


Why is my UPS (Updates Per Second) so low?

There are several reasons why this can happen, the most common is your capture resolution. At the time of this writing the windows capture methods struggle to capture high resolutions under certain circumstances, as a general rule of thumb anything greater then 1200p (1920x1200) starts to suffer from performance issues.

Another cause can be how the game or application you are running is configured. Because of the way windows integrates with the WDM (Windows Desktop Manager) running applications in "Full Screen" mode may in some cases cause a large performance penalty. Try switching to windowed full screen mode, the difference in performance can be like night and day. Titles known to be affected by this are: Fallout76, The BattleField Series and SCUM.

Some titles do some strange things at early initialisation that cause capture performance issues. One such title is the Unigine Valley benchmark where the capture rate is limited to 1/2 the actual rate. For an unknown reason to both myself and the Unigine developers a simple task switch (alt+tab) in and out resolves the issue. This is not a Looking Glass bug.

I'm having mouse issues

Mouse integration is not top priority right now. Consider passing through a hardware mouse. If you can't or won't...

  • Have you tried hitting Scroll Lock to toggle mouse capture mode?
  • Disable guest mouse acceleration (see: Read me first!)
  • Yes, sometimes the cursor position doesn't update until you click. It's a QEMU problem. See points above.

Is my GPU supported?

Your guest GPU almost certainly supports DXGI. Use DxDiag to confirm that you have support for WDDM 1.2 or greater.

  • The server-side (guest) probing error "Capture is not possible, unsupported device or driver" indicates NVidia duplication has failed, not that DXGI has failed.
  • You can make the error go away by specifying "-c DXGI"

Why do I need Spice if I don't want a Spice display device?

You don't need Display Spice enabled. Looking Glass has a Spice client built in to provide some conveniences, but you can disable it with the "-s" argument.

  • Note that without Spice, you will not be sending mouse/keyboard events to the guest.

Where is the host application for Linux?

The "Windows host application" is actually the display server, which runs in the guest VM. The only thing that needs to run in your Linux host OS is the `looking-glass-client` application

Support Looking Glass

Looking Glass is written and released open source by Geoffrey McRae.
If you would like to support this work he accepts donations on the following platforms: