Check that your Raspberry Pis are running with a recent client version (ideally 10.5.0).

Connect your hdmi projector(s) to any raspberry pi and reboot them.

Change your trigger mode to "multiple" and choose "fast auto (2x)".

Now the tricky part is to find the proper timing knowing that the cameras have a specific framerate (110 ms per frame for arducams) and that we have no way to genlock the rolling shutters across the rig. You also need to take into account the projector response time. Here’s a quick diagram to explain the situation:

The green and red frames are the 2 images that are going to be captured. We need to make sure that the green frames have been captured while all the projectors are on and that all the red frames are with projectors off. Ideally the time between frame 1 and 2 is as small as possible.

We’ve managed to achieve good results with arducams using the following settings:

You’ll need to hold the trigger button for a few milliseconds in order to get the projectors ready before you shoot (upon release of the trigger button).