Multi-camera rig vs. Station

[sepehr500]

Hello! I am working with a fixed camera rig that has 4 fisheye cameras all perpendicular to each other( 90 degrees, allowing for a 360 view) with a bit of overlap. Would the best way to add these photos to metashape be with a multicamera rig? if yes, how would I go about setting out the master/slave offset calibration? Camera 1 and 3 are back to back, so i'm assuming the slave offset would not apply? Would this kind of setup also allow metashape to infer scale? Thank you!

[Kiesel]

Hello sepehr500,

1. A camera station assumes that all photos are shot around the projection center (NPP no parallax point). Your multi cammera rig doesn't fullfill this.
2. The projection centers of all 4 cameras have different positions (offsets to each other), that's why they need to be handled as multi camera rig in Metashape.

For that organize the photos from every single camera in an own folder and put all 4 folder in another one (the number of photos in every folder need to be the same). You then can call that upper folder in Workflow/Add Folder and choose Multi-camera system. In the camera calibration dialog you can input offset values for a precalibrated rig. Your multi camera rig will be calibrated in camera alignment process.

Best regards,

Kiesel

[Paulo]

hello,

also important that the 4 cameras are shot at same time (synchronized) so to respect the multicamera rig setup...

[sepehr500]

Thanks for the response! For a 4 camera rig with all cameras perpendicular to each other around a single point, what would the slave offset look like? I'm having difficulty finding documentation on exactly what each part of the slave offset means.

[Paulo]

Hi sepehr,

I think you can have a look at Rigid Camera Rigs section (p. 35) of User Manual for more guidance...In Slave Offset tab you can even let Metashape estimate both location and rotation offset as in first screen capture.

Second screen capture shows offset between Master and Slave1 cameras (at 90deg, looking to horizon and at same level ΔY=0)...from there you can determine other offsets for other cameras...

[Kiesel]

Hi sepher,

you can look for details in the 'Rigid camera rig data' section in the manual at page 23 (page 29 in PDF) and the following pages:

The first subfolder camera will be automatically set as master camera in Camera Calibration dialog, the rest of the cameras will be tackled
as slave cameras to the master. ....

Kiesel

[sepehr500]

Thank you for the responses! My mistake for being unclear with my situation. The 4 cameras are facing away from eachother around the same point. Does this change the recommendations?

[Paulo]

sepehr,

The schema shows exactly this: the master facing front and Slave1 facing right. For each camera, the Z axis represents the camera viewing direction...then you would have Slave2 camera facing back and Slave3 facing left...

PD. i you have a sample of a few of the  4 camera rig images to share we could have a look at it and recommend further...

[sepehr500]

Thanks Paul. Thanks for posting that configuration. I will give it a shot and let you know how it goes!