function idx = bp_near(pos, p, r)
% BP_NEAR Beads near a point.
%   idx = bp_near(pos, p, r) returns the beads within distance r of point p
%   (1-by-3). With r = 0, or if no bead is that close, returns the nearest bead.
if numel(p) == 2
    p = [p(:)', 0];
end
d = vecnorm(pos - p(:)', 2, 2);
idx = find(d <= r);
if isempty(idx)
    [~, idx] = min(d);
end
end