pub fn basis_for(dir: DVec3) -> (DVec3, DVec3)Expand description
Two unit vectors completing an orthonormal frame with dir.
dir must be normalised. The helper axis is chosen by which component of
dir is small, which keeps the cross product well conditioned — picking a
fixed helper would give a near-zero cross product whenever dir happened to
be parallel to it, and the resulting basis would be numerical noise.