Multiple GPU

i want to run 5 projectors plus 1 GUI monitor from a single system.
can lightact utilize multiple gpu’s?
setup would be:
win 10 pro 64bit
2x quadro rtx4000,
preferable in mosaic mode with nvidia sync
(no sync card, just the cable i think, forgot the definition…)
although, if i need to genlock the system,
can lightact utilize the nvidia sync card?


Our usual workflow with more projectors than GPU outputs would be to use a video splitter. We often use Datapath FX4. It allows you to split, say a 4K output into 4xHD outputs. If you go that way, please be aware that LightAct’s FPS will only be as high as the lowest FPS of all connected devices.

I don’t think LightAct can work efficiently with 2GPUs.

On the other hand, it might be worth trying with mosaic, as we haven’t done that yet. If you do, please let me know. :slight_smile:

LightAct can work with Quadro Sync cards. To be honest, they are working on a much lower hardware level, so I would say any software can use them. All they do is they make sure all GPUs render their frames at the exact same time. It doesn’t ‘touch’ LightAct in any way actually.


Hi there,

We base our studio on a single system. I prefered to use multi GPU in order to reduced latency with FX4 cause we works a lot on interactive purpose.

we have 8 VP (epson EB-L1075) over 2 x quadro RTX5000 with sync card + RTX 4000 for monitoring.
I’m still waiting the nvlink connector in order to share VRAM between the both RTX5000. We use a large mozaic desktop of 8 x 1 projector.

At this time it works quite well. But we have to define the mozaic desktop as the primary desktop in windows.
When we use spout app, it has to be launch on the primary desktop + focus lightact app to get full perf.

If you want I test something just tell me.

Hi John,

Glad to hear from you, but I’m not sure I understand what exactly is the problem. AFAIK, Spout works only on a single GPU and it doesn’t allow texture sharing. Please let me know if otherwise.

Also, what do you use for content? If I remember correctly from our email conversations, its Unity, correct?


There is no problem, just XP sharing.

For now the workflow in light act, there is a canvas containing the UV of the 3D model of the cyclorama.
Then, I place several “render to canvas” with different kind of input possibility, spout from Unity / NDI / BP card . And at the end of the pipe, when the UV is textured, I send it in a variable to map the UV on the 3D model.
Our studio can welcome artists with their own laptop, so but this way, They can throw content surface by surface or directly the entire UV through NDI for example without taking care the videoprojector mapping.
For us, we mainly run our unity app into the media server.

Oh ok. For a moment there, I jumped straight to ‘post on AnswerHub equals someone has a problem’ conclusion :slight_smile:

Even better. Please feel free to share images & videos and we will be happy to include a project summary in our Showcase section.

Looking forward to it!