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3D graphics acceleration over Remote Desktop

A friend of mine tipped me off to an interesting post on DIRECTXDEV about GPU acceleration over Remote Desktop. After some investigation with a couple of machines, I discovered that yes, it is actually true that you can run 3D apps over Remote Desktop (Terminal Server). The key is that the machine you are remoting into must be running Windows Vista with a WDDM driver. Beyond that, it actually works as expected, although a bit slow. Some details:

Now, the downside: it's slow. Really slow. So slow that I'd say it's basically unusable unless you're on a LAN, and a fast one at that. It looks like Terminal Services tries to send over the data from every Present(), and it blocks the app until that happens, instead of just skipping frames. It eats a lot of CPU in the process, too, instead of just waiting. I was just barely able to push 640x360 video at 24 fps with VirtualDub's D3D9 display minidriver, which was throwing about 10MB/sec across the gigabit LAN here -- probably about the best that the consumer-level hub can do. Readback doesn't seem to be a problem, at least not on the GeForce 6 and 8 cards I have here, because everything speeds back up if you cover enough of the 3D window.

Basically, this means that 3D support is usable with apps that just use it for 2D acceleration or otherwise static rendering, but anything dynamic like a video player or a game is going to be far too slow. It might be more viable if Microsoft had implemented frame dropping, but it looks like VNC may still be better for that. What this is definitely good for, though, is running GPU accelerated apps remotely. On XP, this isn't possible over Remote Desktop because as soon as you log in all your apps are pushed onto the software-only driver. On Vista, though, they could continue to run on the server-side GPU, and performance isn't a problem if the app isn't displaying the result continuously.


This blog was originally open for comments when this entry was first posted, but was later closed and then removed due to spam and after a migration away from the original blog software. Unfortunately, it would have been a lot of work to reformat the comments to republish them. The author thanks everyone who posted comments and added to the discussion.