• 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).

Lighting in fast_auto 2x

Xangle offers 2 ways to control the lighting of the 2 exposures in fast_auto mode.

Method 1: GPIO controled leds

If you can control the intensity of your leds with GPIO, then it is possible to change the GPIO output before and between the exposures. The settings are not exposed in the XangleCS graphical user interface but you can edit the server_settings.json file in the /config folder of xangle working directory and restart the app.

The relevant section of server_settings.json is:

 "projector": {
        "min_shot_delay": 230,
        "gpio_delay": 100,
        "clear_screen_delay": 100,
        "shot_1": {
            "mapping": [
                {
                    "pin": 4,
                    "value": "HIGH"
                },
                {
                    "pin": 17,
                    "value": "HIGH"
                },
                {
                    "pin": 19,
                    "value": "HIGH"
                },
                {
                    "pin": 22,
                    "value": "LOW"
                },
                {
                    "pin": 27,
                    "value": "LOW"
                }
            ]
        },
        "shot_2": {
            "mapping": [
                {
                    "pin": 4,
                    "value": "LOW"
                },
                {
                    "pin": 17,
                    "value": "LOW"
                },
                {
                    "pin": 19,
                    "value": "LOW"
                },
                {
                    "pin": 22,
                    "value": "LOW"
                },
                {
                    "pin": 27,
                    "value": "LOW"
                }
            ]
        }
    }

shot1 and shot2 refer to the 2 exposures.

Method2: Xangle board with leds support (requires 2024-12-03 or newer)

If you have pis equipped with a xangle board and a compatible led strips, it is possible to instruct xangle to change the lighting between the 2 shots. The settings are directly available in the fast_auto trigger mode settings panel:

For performance reasons, the settings are "global" meaning it is not possible to fine tune the settings "per raspberry pi group" like you do in the /lights panel. We need to assume that all led strips are identical in "type" and the settings for each iteration are broadcasted.