FUNCTION first_proj_axis

(* SCHEMA building_design_schema; *)

  FUNCTION first_proj_axis(
               z_axis, arg: direction
      ): direction;

    LOCAL
      x_vec  : vector;
      v      : direction;
      z      : direction;
      x_axis : direction;
    END_LOCAL;
    IF (NOT EXISTS(z_axis)) OR (NOT EXISTS(arg)) OR (arg.dim <> 3) THEN
      x_axis := ?;
    ELSE
      z_axis := normalise(z_axis);
      IF NOT EXISTS(arg) THEN
        IF z_axis <> direction([1,0,0]) THEN
          v := direction([1,0,0]);
        ELSE
          v := direction([0,1,0]);
        END_IF;
      ELSE
        IF cross_product(arg,z).magnitude = 0 THEN
          RETURN(?);
        ELSE
          v := normalise(arg);
        END_IF;
      END_IF;
      x_vec := scalar_times_vector(dot_product(v,z),z_axis);
      x_axis := vector_difference(v,x_vec).orientation;
      x_axis := normalise(x_axis);
    END_IF;
    RETURN(x_axis);

  END_FUNCTION; -- first_proj_axis

Referenced By

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2012-03-27T17:18:14-04:00