geom:arrow

(geom:arrow &key length direction radius head-radius head-length sides color label)

An arrow as a SOLID: a shaft and a pointed head, built as one shell rather than a union of a cylinder and a cone. The tail is the model origin and the tip is length along direction (:x / :y / :z / :-x ... or a vector). :radius is the shaft's, so its thickness is twice that; the head is a cone of :head-radius over the last :head-length. Every unstated measurement is a fraction of :length, so naming the length alone gives the same arrow at any size. Three of them are geom:triad, the origin indicator. See the solid modeling guide.