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1 ## Copyright (C) 2007 Michael Goffioul, Kai Habel |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} cylinder |
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21 ## @deftypefnx {Function File} {} cylinder (@var{r}) |
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22 ## @deftypefnx {Function File} {} cylinder (@var{r}, @var{n}) |
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23 ## @deftypefnx {Function File} {[@var{x}, @var{y}, @var{z}] =} cylinder (@dots{}) |
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24 ## @deftypefnx {Function File} {} cylinder (@var{ax}, @dots{}) |
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25 ## Generates three matrices in @code{meshgrid} format, such that |
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26 ## @code{surf (@var{x}, @var{y}, @var{z})} generates a unit cylinder. |
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27 ## The matrices are of size @code{@var{n}+1}-by-@code{@var{n}+1}. |
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28 ## @var{r} is a vector containing the radius along the z-axis. |
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29 ## If @var{n} or @var{r} are omitted then default values of 20 or [1 1] |
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30 ## are assumed. |
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31 ## |
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32 ## Called with no return arguments, @code{cylinder} calls directly |
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33 ## @code{surf (@var{x}, @var{y}, @var{z})}. If an axes handle @var{ax} |
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34 ## is passed as the first argument, the surface is plotted to this set |
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35 ## of axes. |
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36 ## |
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37 ## Examples: |
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38 ## @example |
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39 ## disp ("plotting a cone") |
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40 ## [x, y, z] = cylinder (10:-1:0,50); |
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41 ## surf (x, y, z); |
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42 ## @end example |
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43 ## @seealso{sphere} |
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44 ## @end deftypefn |
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45 |
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46 function [xx, yy, zz] = cylinder (varargin) |
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47 |
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48 [ax, args, nargs] = __plt_get_axis_arg__ ((nargout > 0), "cylinder", |
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49 varargin{:}); |
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50 |
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51 if (nargs == 0) |
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52 n = 20; |
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53 r = [1, 1]; |
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54 elseif (nargs == 1) |
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55 n = 20; |
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56 r = args{1}; |
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57 elseif (nargs == 2) |
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58 r = args{1}; |
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59 n = args{2}; |
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60 else |
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61 print_usage (); |
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62 endif |
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63 |
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64 if (length (r) < 2) |
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65 error ("cylinder: length(r) must be larger than 2") |
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66 endif |
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67 |
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68 phi = linspace (0, 2*pi, n+1); |
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69 idx = 1:length(r); |
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70 [phi, idx] = meshgrid(phi, idx); |
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71 z = (idx - 1) / (length(r) - 1); |
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72 r = r(idx); |
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73 [x, y] = pol2cart (phi, r); |
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74 |
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75 if (nargout > 0) |
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76 xx = x; |
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77 yy = y; |
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78 zz = z; |
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79 else |
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80 surf (ax, x, y, z); |
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81 endif |
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82 |
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83 endfunction |
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84 |
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85 %!demo |
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86 %! disp ("plotting a cone") |
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87 %! [x, y, z] = cylinder (10:-1:0,50); |
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88 %! surf (x, y, z); |
