geom:triad

(geom:triad &key length radius head-radius head-length sides at)

The three arrows a coordinate frame is drawn as -- +x red, +y green, +z blue, labelled "x" / "y" / "z" -- as a LIST of geom:arrow solids the caller owns, not a viewer mode. :at places all three, so (geom:triad :at (geom:vec3 0 0 0)) is the origin indicator; add them like any other solid with (scene:add *v* (geom:triad)), since scene:add splices a list argument. The default length is the one scene:axes' line triad draws at the viewer's default camera distance. See the solid modeling guide.