Cartoon gap cutoff
With cartoon_gap_cutoff > 0, if there are missing residues along the protein backbone (e.g. missing loops), PyMOL will create a dashed cartoon loop segment if the gap (in number of residues) is shorter than the cutoff.
New in PyMOL 1.8.2
set cartoon_gap_cutoff, 10 fetch 2xwu, async=0 as cartoon orient B//152-156/
Number of dashes
The number of dashes is directly affected by the cartoon_sampling setting:
set cartoon_sampling, 20