Image:Rotation illustration2.svg

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Rotation_illustration2.svg (SVG file, nominally 875 × 758 pixels, file size: 47 KB)

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Description

Illustration of en:Rotation (mathematics)

Source

self-made, with MATLAB, then tweaked with en:Inkscape

Date

02:28, 9 June 2007 (UTC)

Author

Oleg Alexandrov

Permission
(Reusing this image)

see below



Public domain I, the copyright holder of this work, hereby release it into the public domain. This applies worldwide.

In case this is not legally possible:
I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.


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[edit] Source code


function main()

% prepare the screen
   figure(1); clf; hold on; axis equal;  axis off; 
   linewidth=2; fs= 30;

   N = 11;
   a = -2; b = N+a-1;
   blue = [0, 0, 1];
   red = [1, 0, 0];
   gray=[0.7, 0.7, 1.0];
   white = 0.99*[1, 1, 1];
   lightblue=[176, 196,222]/256;
   green = [0, 200,  70]/256;
   color1 = gray;
   color2 = green;

   XX = linspace(a, b, N); YY = XX;
   [X, Y] = meshgrid(XX, YY);

   factor = 4; shift = 3.6;
   x=factor*[0, 0.7, 0.5 1, 0]+shift; y=factor*[0, 0, 0.5, 1 0.8];
   do_plot(x, y, X, Y, linewidth, color1);

   theta=1.4*pi/4; A=[cos(theta) -sin(theta); sin(theta) cos(theta)];
   for i=1:N
          for j=1:N
                 v= A*[X(i, j); Y(i, j)]; X(i, j)=v(1); Y(i, j)=v(2);
          end
   end
   for i=1:length(x)
          v= A*[x(i); y(i)]; x(i)=v(1); y(i)=v(2); 
   end

   do_plot(x, y, X, Y, linewidth, color2);

% plot the point around which the rotation takes place
   ball_radius = 0.15;
   ball(0, 0, ball_radius, red);
   text(0, -0.5, '{\it O}', 'color', red, 'fontsize', fs)

% plot the arrow suggesting the rotation
   factor = 4;
   x=factor*1.7; y=factor*2.1; r=sqrt(x^2+y^2); thetas=atan2(y, x);
   thetae=0.7*theta+thetas;
   Theta=thetas:0.01:thetae; X=r*cos(Theta); Y=r*sin(Theta);
   plot(X, Y, 'linewidth', linewidth, 'color', red)
   n=length(Theta);
   arrow([X(n-2), Y(n-2)], [2*X(n)-X(n-1), 2*Y(n)-Y(n-1)], linewidth, 1, 30, linewidth, red)

% plot two invisible points, to bypass a saving bug
   plot(a, 1.5*b, 'color', white); 
   plot(a, -0.5*b, 'color', white); 

% save to eps and to svg
%saveas(gcf, 'rotation_illustration2.eps', 'psc2') 
   plot2svg('rotation_illustration2.svg')

function do_plot(x, y, X, Y, linewidth, color)
   n=length(x); 
   P=5; Q=n+2*P+1; % P will denote the amount of overlap

% Make the 'periodic' sequence xp=[x(1) x(2) x(3) ... x(n) x(1) x(2) x(3) ... ]
% of length Q. Same for yp.
   for i=1:Q
          j=rem(i, n)+1; % rem() is the remainder of division of i by n
          xp(i)=x(j);
          yp(i)=y(j);
   end

% do the spline interpolation
   t=1:length(xp);
   N=100; % how fine to make the interpolation
   tt=1:(1/N):length(xp);
   xx=spline(t, xp, tt);
   yy=spline(t, yp, tt);

% discard the reduntant pieces
   start=N*(P-1)+1;
   stop=N*(n+P-1)+1;
   xx=xx(start:stop); 
   yy=yy(start:stop);

   H=fill(xx, yy, color);

   set(H, 'linewidth', 1, 'edgecolor', color);

   [M, N]= size(X);
   for i=1:N
          plot([X(1, i), X(N, i)], [Y(1, i), Y(N, i)], 'linewidth', linewidth, 'color', color)
          plot([X(i, 1), X(i, N)], [Y(i, 1), Y(i, N)], 'linewidth', linewidth, 'color', color)
   end

% plot some balls, avoid artifacts at the corners
   small_rad=0.045;
   ball(X(1, 1), Y(1, 1), small_rad, color)
   ball(X(1, N), Y(1, N), small_rad, color)
   ball(X(N, 1), Y(N, 1), small_rad, color)
   ball(X(N, N), Y(N, N), small_rad, color)

function arrow(start, stop, th, arrow_size, sharpness, arrow_type, color)
   
% Function arguments:
% start, stop:  start and end coordinates of arrow, vectors of size 2
% th:           thickness of arrow stick
% arrow_size:   the size of the two sides of the angle in this picture ->
% sharpness:    angle between the arrow stick and arrow side, in degrees
% arrow_type:   1 for filled arrow, otherwise the arrow will be just two segments
% color:        arrow color, a vector of length three with values in [0, 1]
   
% convert to complex numbers
   i=sqrt(-1);
   start=start(1)+i*start(2); stop=stop(1)+i*stop(2);
   rotate_angle=exp(i*pi*sharpness/180);

% points making up the arrow tip (besides the "stop" point)
   point1 = stop - (arrow_size*rotate_angle)*(stop-start)/abs(stop-start);
   point2 = stop - (arrow_size/rotate_angle)*(stop-start)/abs(stop-start);

   if arrow_type==1 % filled arrow

% plot the stick, but not till the end, looks bad
      t=0.5*arrow_size*cos(pi*sharpness/180)/abs(stop-start); stop1=t*start+(1-t)*stop;
      plot(real([start, stop1]), imag([start, stop1]), 'LineWidth', th, 'Color', color);

% fill the arrow
      H=fill(real([stop, point1, point2]), imag([stop, point1, point2]), color);
      set(H, 'EdgeColor', 'none')
      
   else % two-segment arrow
      plot(real([start, stop]), imag([start, stop]),   'LineWidth', th, 'Color', color); 
      plot(real([point1, stop, point2]), imag([point1, stop, point2]), 'LineWidth', th, 'Color', color);
   end

function ball(x, y, radius, color) % draw a ball of given uniform color 
   Theta=0:0.1:2*pi;
   X=radius*cos(Theta)+x;
   Y=radius*sin(Theta)+y;
   H=fill(X, Y, color);
   set(H, 'EdgeColor', color);


File history

Click on a date/time to view the file as it appeared at that time.

Date/TimeDimensionsUserComment
current03:36, 11 June 2007875×758 (47 KB)Oleg Alexandrov (tweak)
05:24, 10 June 2007875×758 (47 KB)Oleg Alexandrov (Tweak.)
05:55, 9 June 2007875×874 (40 KB)Oleg Alexandrov (tweak)
05:45, 9 June 2007200×200 (37 KB)Oleg Alexandrov (tweak )
02:28, 9 June 2007200×200 (35 KB)Oleg Alexandrov ({{Information |Description= Illustration of en:Rotation (mathematics) |Source=self-made, with MATLAB, then tweaked with en:Inkscape |Date= ~~~~~ |Author= Oleg Alexandrov }} {{PD-self}})
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