Commit ceee01b4 by Liam M. Healy

### Fix #'right-angle

```The function right-angle will find an arbitrary vector in the plane
perpendicular to a given vector. It would possibly return the zero
vector. This version is shorter and should always produce a non-zero
vector.```
parent a72ecaf6
 ;; Functions on cartesian space ;; Liam Healy 2010-12-26 20:58:14EST cartesian.lisp ;; Time-stamp: <2012-06-03 22:34:26EDT cartesian.lisp> ;; Time-stamp: <2013-10-22 18:18:45EDT cartesian.lisp> ;; Copyright 2011, 2012 Liam M. Healy ;; Copyright 2011, 2012, 2013 Liam M. Healy ;; Distributed under the terms of the GNU General Public License ;; ;; This program is free software: you can redistribute it and/or modify ... ... @@ -32,20 +32,16 @@ (defun right-angle (vector) "Find an arbitrary right angle to the vector." (let* ((vec (pqval vector)) (bigind ;; Find which component is the largest (iterate (for i vector-element-index vector) (finding i maximizing (abs (grid:aref vec i))))) (project (grid:copy-to vec)) (return (grid:copy-to vec))) ;; Find vector projected into the plane perpendicular (setf (grid:aref project bigind) 0.0 ;; The return vector is the original vector with a different ;; value in what was the largest component. (grid:aref return bigind) (cl:- (cl:/ (grid:inner project project) (grid:aref vec bigind)))) (grid:normalize return))) ;; See [[id:7154d151-388f-48d9-b1d1-ca811fc04222][Perpendicular vector]] ;; See http://www.gamedev.net/topic/572770-finding-vector-perpendicular-to-line-in-3d/ ;; Take the cross product with the coordinate unit vector of the smallest component. (let ((vec (pqval vector))) (grid:normalize (grid:cross vec (coordinate-unit-vector (iterate (for i vector-element-index vec) (finding i minimizing (abs (grid:aref vec i))))))))) (defun coplanar (vect1-or-matrix &optional vect2 vect3) "The cosine of the angle between vect1 and the cross product of vect2 and vect3. ... ...
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