// Find a nonblocked ray from source to target. Return false if no
// such ray could be found, otherwise return true and fill ray
// appropriately.
// if range is too great or all rays are blocked.
// If cycle_dir is 0, find the first fitting ray. If it is 1 or -1,
// assume that ray is appropriately filled in, and look for the next
// ray in that cycle direction.
// If find_shortest is true, examine all rays that hit the target and
// take the shortest (starting at ray.fullray_idx).

// Coordinate transformation so we can find_ray quadrant-by-quadrant.
// TODO: Unify with los_params.

// Find a nonblocked ray from source to target. Return false if no
// such ray could be found, otherwise return true and fill ray
// appropriately.
// if range is too great or all rays are blocked.
// If cycle_dir is 0, find the first fitting ray. If it is 1 or -1,
// assume that ray is appropriately filled in, and look for the next
// ray in that cycle direction.
// If find_shortest is true, examine all rays that hit the target and
// take the shortest (starting at ray.fullray_idx).

// Returns a straight ray from source to target.