Hi, I am trying to model the ZED Mini as a pinhole camera in sim and wanted clarification on where the coordinate system should be defined from assuming I am just using the left camera.
Hi @Avi
Welcome to the StereoLabs community.
You can find all the relevant information concerning your questions on the online documentation:
Concerning calibration:
Hi, from theses I see extrinisics between the left and right sensors provided, but what about extrinsics from some point in the camera body to left sensor? I believe there should be mechanical drawings of the camera that show where the sensor is located when manufacturing the camera.
Hi Avinash,
The ZED SDK expresses everything (images, depth, poses) in a frame whose origin is the left camera’s optical center, so that is exactly where your pinhole camera should be placed in sim.
For the position of that optical center relative to the camera body, you can download the official STEP/CAD model of the ZED Mini from stereolabs.com/3dmodels and measure from the mounting holes or any housing datum. As a nominal reference, our ROS 2 URDF places the left optical center at y = +31.5 mm (half the 63 mm baseline) and z = +13.25 mm above the bottom plane, measured from the center of the bottom face where the 1/4"-20 mount is.
Keep in mind these are nominal design values; the per-unit factory calibration only refines the left-right and camera-IMU transforms, so for millimeter-exact placement please rely on the STEP models.
Best regards,
Tristan
Thank you Tristan. Something I’ve noticed when doing some testing it seems as if the image from the leftmat in is some optical frame between the two cameras. Is this a specific mode/as a result of the rectification and can it be turned off?
Hi Avi,
VIEW::LEFT is rectified: both images are rotated onto a common “perfect stereo rig” orientation with a shared principal point, which is why it can look like a frame between the lenses. It is only a rotation about the optical center though, so the viewpoint is still the physical left lens.
You can get the native image with VIEW::LEFT_UNRECTIFIED (intrinsics in calibration_parameters_raw), but for a sim pinhole I would keep the rectified one: it is already a distortion-free pinhole at the left lens, and depth, point cloud and pose all use that frame.
Best regards,
Tristan