--rotate

--rotate accepts a floating-point value in degrees and rotates every loaded object around the Z axis by that amount before slicing. The value is converted to radians internally and passed directly to the object's rotation routine. The default is 0 (no rotation), there are no constraints on the range, and negative values are accepted.

The rotation is applied to the object's raw mesh geometry (volumes), not to the instance placement transform stored in a 3MF. After rotating each volume, the slicer recenters the entire object so its bounding box center is at the geometric origin. A consequence is that any existing XY offset baked into the volumes is reset: the rotated mesh lands at the origin, then whatever instance placement the 3MF recorded is applied on top. When slicing a 3MF that has explicit per-plate positions, that instance transform survives and compounds with the newly recentered geometry, which can shift the object away from its intended plate position.

The flag is a transform, processed in command-line order alongside --rotate-x and --rotate-y (which rotate around the X and Y axes respectively). It applies to every object in every model loaded in the same invocation; there is no per-object targeting. Because rotate is a scalar config key, supplying it more than once does not stack the angles: the config stores only the last supplied value, and the key is dispatched only once. --arrange applied after rotation repositions the already-rotated footprint on the bed, leaving the rotation intact.