function gear3d(varargin)

%GEAR3D   GUI example of 3D gear.
%   GEAR3D will pop up a GUI example of 3D gear. The gear rolls on a geared
%   ground based on the mouse location. It uses the x-location of the mouse
%   pointer for the gear location. Use the arrow keys to change the view.
%   Press SPACEBAR to reset the view. This was inspired by Mike Agostini's
%   3D Clock submission in FEX:
%
%
%   The gear is made of 2 surface objects, and the ground is a single surface
%   object. Since the moving part (gear) only contains 2 objects, the
%   animation update is quite smooth. It uses OpenGL rendering.
%
%   GEAR3D accepts 3 optional arguments that specify the number of teeth on the
%   gear, number of spokes, and the gear ratio between the ground and the gear.
%
%   Example:
%     GEAR3D('teeth', 30)   - default is 50.
%     GEAR3D('spokes', 4)   - default is 8.
%     GEAR3D('ratio', 2)    - default is 3. This also determines how big
%                             the ground radius is.
%   Only positive integers are allowed.
%
%   This has no practical use. I made it as an exercise for 3d animation.
%   You have been warned. This was created in R13SP1, so nested function is
%   not utilized. Nested function will improve how surface data are passed
%   between functions.
%
%   VERSIONS:
%   v1.0 - first version
%   v1.1 - fixed gear meshing problem. (Feb 2, 2006)
%   v1.2 - changed to pass parameters instead of using handles structure
%          (for speed). also inlined the stripped down version of the ROTATE
%          function to speed up animation (Feb 25, 2006)
%

%   Jiro Doke
%   Feb 3, 2006


%--------------------------------------------------------------------------
% Default values
%--------------------------------------------------------------------------

% Number of teeth
numteeth  = 50;
% Number of spokes
numspokes = 8;
% Gear ratio
rr        = 3;

%--------------------------------------------------------------------------
% Optional arguments
%--------------------------------------------------------------------------

if mod(nargin, 2) == 1
  error('Optional arguments must come in pairs.');
end
if nargin
  opt = varargin(1:2:end);
  val = varargin(2:2:end);
  validOpts = {'teeth', 'spokes', 'ratio'};
  for iArg = 1:length(opt)
    id = strmatch(lower(opt{iArg}), validOpts);
    if isempty(id)
      error('Invalid option. Valid options: ''teeth'', ''spokes'', ''ratio''');
    else
      switch strmatch(lower(opt{iArg}), validOpts)
        
        case 1
          if isnumeric(val{iArg}) & length(val{iArg}) == 1
            numteeth = round(abs(val{iArg}));
          end
         
        case 2
          if isnumeric(val{iArg}) & length(val{iArg}) == 1
            numspokes = round(abs(val{iArg}));
          end
         
        case 3
          if isnumeric(val{iArg}) & length(val{iArg}) == 1
            rr = round(abs(val{iArg}));
          end
         
      end
    end
  end
end

%--------------------------------------------------------------------------
% Construct gear and ground
%--------------------------------------------------------------------------

% Gear part radii
r1 = 1;
r2 = 3;
r3 = 10;
r4 = 11;
r5 = 13;
r6 = 12;

% Radius to the center of gear teeth
r = (r5 + r6) / 2;

% Height of gear teeth
h = r5 - r6;

% Radius to the center of ground teeth
l = r * rr;

% Ground radii
l1 = l  - h/2;
l2 = l  + h/2;
l3 = l2 + 2;

% Gear
[x0,y0,z0]       = cylinder([r6], numteeth*4);  % teeth groove
[x1,y1,z1]       = cylinder([r1, r1, r2, r2, r1], numteeth*4);  % spokes
[x2,y2,z2]       = cylinder([r3, r3, r4, r4, r5, r5, r4, r4, r3], numteeth*4);  % gear teeth
z1([1, 4, 5], :) =  2;
z1(2:3, :)       = -2;
z2([1, 8, 9], :) =  2;
z2(2:3, :)       = -2;
z2(4:5, :)       = -1;
z2(6:7, :)       =  1;
x2(5:6,1:4:end)  = x0(1:2,1:4:end);
x2(5:6,2:4:end)  = x0(1:2,2:4:end);
y2(5:6,1:4:end)  = y0(1:2,1:4:end);
y2(5:6,2:4:end)  = y0(1:2,2:4:end);

% Spoke
interval  = round(length(x1) / numspokes);
for id = 1:4
  x1(3:4, id:interval:end) = x2(1:2, id:interval:end);
  y1(3:4, id:interval:end) = y2(1:2, id:interval:end);
end

% Ground
[x3, y3, z3]         = cylinder([l2, l2, l3, l3, l2], numteeth * rr * 4);
[x4, y4, z4]         = cylinder(l1, numteeth * rr * 4);
z3([1 4 5], :)       =  4;
z3([2 3], :)         = -4;
x3([1 2 5], 1:4:end) = x4([1 1 1], 1:4:end);
x3([1 2 5], 2:4:end) = x4([1 1 1], 2:4:end);
y3([1 2 5], 1:4:end) = y4([1 1 1], 1:4:end);
y3([1 2 5], 2:4:end) = y4([1 1 1], 2:4:end);

% Make ground a half circle
len            = round(length(x3) / 2);
x3(:, len:end) = [];
y3(:, len:end) = [];
z3(:, len:end) = [];

%--------------------------------------------------------------------------
% GUI
%--------------------------------------------------------------------------

% Create figure;
fH = findobj('Type', 'figure', 'Tag', 'solidmodelGUI');
if ishandle(fH)
  close(fH);
end
fH = figure(...
  'Name'       , sprintf('3D Gear: View = [%3.0f, %3.0f]', 0, -50), ...
  'NumberTitle', 'off', ...
  'Units'      , 'normalized', ...
  'Position'   , [.1, .1, .8, .8], ...
  'Visible'    , 'off', ...
  'Tag'        , 'solidmodelGUI');

axes(...
  'Units'   , 'normalized', ...
  'Position', [0, .9, 1, .1], ...
  'XLim'    , [-1, 1], ...
  'YLim'    , [-1, 1], ...
  'Visible' , 'off');
text(0, 0, ...
  {'Move the mouse left and right within the figure window to move the gear.',...
    'Use ARROW keys to change the view. SPACE to reset view.'}, ...
  'HorizontalAlignment' , 'center', ...
  'VerticalAlignment'   , 'middle', ...
  'Color'               , 'red');

axH = axes('Units', 'normalized', ...
  'Position', [0, 0, 1, .9]);

% Gear
%
% Spokes
gearH(1) = surface(x1,y1,z1, ...
  'EdgeColor', [.3, .3, .3], ...
  'EdgeAlpha',  0, ...
  'FaceColor', [.5, .5, 1]);
% Gear Teeth
gearH(2) = surface(x2,y2,z2, ...
  'EdgeColor', [.3, .3, .3], ...
  'EdgeAlpha', .1, ...
  'FaceColor', [.5, .5, 1]);

% Ground
surface(x3,y3,z3, ...
  'EdgeColor', [.3, .3, .3], ...
  'EdgeAlpha', .1, ...
  'FaceColor', [.5, 1, .5], ...
  'FaceAlpha', .5);

set(axH, 'View', [0, -50]);
axis equal manual off;
set(axH, 'CameraViewAngleMode', 'manual');

% Add lighting
light('Position', [50 , 0, -20]);
light('Position', [-50, 0, -20]);

% Calculate size once and pass in as parameter
sz1 = size(x1);
sz2 = size(x2);

set(fH, ...
  'Visible'              , 'on', ...
  'KeyPressFcn'          , {@myKeyPressFcn, axH}, ...
  'WindowButtonMotionFcn', {@myMotionFcn, gearH, x1, x2, y1, y2, r, l, sz1, sz2});

% Set initial position of gear
myMotionFcn(gcf, [], gearH, x1, x2, y1, y2, r, l, sz1, sz2);


%--------------------------------------------------------------------------
% myKeyPressFcn - process key presses to rotate view
%--------------------------------------------------------------------------
function myKeyPressFcn(obj, edata, axH)

k = get(obj, 'CurrentKey');
aZeL = get(axH, 'View');

switch lower(k)
  case 'uparrow'
    aZeL(2) = min([aZeL(2) + 10,  90]);
  case 'downarrow'
    % -90 doesn't work well when rotated left or right
    aZeL(2) = max([aZeL(2) - 10, -89.9999]);
  case 'leftarrow'
    aZeL(1) = max([aZeL(1) - 10, -90]);
  case 'rightarrow'
    aZeL(1) = min([aZeL(1) + 10,  90]);
  case 'space'
    aZeL    = [0, -50];
end

set(axH, 'View', aZeL);
set(obj, 'Name', sprintf('3D Gear: View = [%3.0f, %3.0f]', aZeL));


%--------------------------------------------------------------------------
% myMotionFcn - move mouse to move gear
%--------------------------------------------------------------------------
function myMotionFcn(obj, edata, gearH, x1, x2, y1, y2, r, l, sz1, sz2)

pt = get(obj, 'CurrentPoint');

d = l - r;

% Get center location of gear
x0 = -d + pt(1) * d * 2;
y0 = sqrt(abs(d^2 - x0^2));

% Get amount of gear rotation
th1 = atan2(x0, y0) - pi/2;
th = (th1 - (th1 * (l / r)));

%--------------------------------------------------------------------------
% Rotate gear (from ROTATE)
%--------------------------------------------------------------------------
% Calculate rotation matrix
cosa = cos(-th);
sina = sin(-th);
rot  = [cosa, -sina; sina, cosa]';

newxy1   = [x1(:), y1(:)];
newxy2   = [x2(:), y2(:)];
newxy1   = newxy1 * rot;
newxy2   = newxy2 * rot;
newx1    = x0 + reshape(newxy1(:, 1), sz1);
newy1    = y0 + reshape(newxy1(:, 2), sz1);
newx2    = x0 + reshape(newxy2(:, 1), sz2);
newy2    = y0 + reshape(newxy2(:, 2), sz2);

% Set new position for the gear
set(gearH, {'XData', 'YData'}, {newx1, newy1; newx2, newy2});

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