Moving sources

Rays, Beams, beamlets like the GaussianBeamlet and groups of beams can be repositioned with the commands listed in the Kinematics section.

Every move resets the source

A traced beam/beamlet whose start is moved would otherwise keep stale rays and child beams from the old, now geometrically wrong, light path. To avoid this, every call to one of the translation, rotation or reset commands first resets the moved beam (or, for a group, every one of its beams) to its untraced start state: all rays beyond the start ray (of every component beam of a beamlet) are dropped, and any child beams (e.g. created by a beamsplitter interaction) are removed. Call solve_system! again after moving a source to retrace it. set_pivot3d! is the exception, see below.

using BeamletOptics

beam = Beam([0, 0, 0], [0, 1, 0])
translate3d!(beam, [1, 0, 0])     # shift the start by [1, 0, 0], resets the beam
zrotate3d!(beam, deg2rad(90))     # rotate 90° about z through the (new) start position

Rays and beams

The pivot used for rotations is the start of the beam, i.e. the position of its first/chief ray (the chief ray of a GaussianBeamlet or AstigmaticGaussianBeamlet). reset_translation3d! moves this start back to the global origin. Rays and single beams have no orientation, only a direction, so reset_rotation3d! throws an ArgumentError for them — use align3d! instead.

Polarized rays

Rotating a PolarizedRay (including the chief ray of an AstigmaticGaussianBeamlet) also rotates its field vector E0 together with the direction, so it stays orthogonal to the new propagation direction.

Only a root beam can be moved. Calling a kinematic command on a child beam, e.g. one created by a beamsplitter interaction during tracing, throws an ArgumentError — move the root beam instead.

Beam groups

For a BeamletOptics.AbstractBeamGroup, the pivot is the group's center, so that all member beams are rotated rigidly about the source origin. Rotating a group also updates its orientation, so a roll about the group's own optical axis is tracked. reset_translation3d! moves the center back to the global origin, and reset_rotation3d! moves the group back to orientation = identity (optical axis along +y). Refer to BeamletOptics.AbstractBeamGroup for the orientation convention.

set_pivot3d! moves a group's center to a new pivot without moving or resetting its beams, e.g. to rotate3d! a group about one of its own beams instead of its default center.

BeamletOptics.set_pivot3d! Method

set_pivot3d!(bg::AbstractBeamGroup, pivot)

Moves the kinematic pivot (center) of the beam group bg to pivot, without moving or resetting any of its beams. The pivot is the reference point used by rotate3d! and reset_translation3d!; the group orientation is unchanged.

Unlike translate3d! or rotate3d!, this only changes bookkeeping and does not reset already traced beams.

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