Rework the ellipse plotting routines.

src/@epicell/epicell.m

@@ -84,6 +84,16 @@ classdef epicell
                 'LineWidth', 1, ...
                 'Marker', '.' );
         end
+                
+        % Plot a 2D ellipse in 3D.
+        h = plot_ellipse_3d( obj, npoints, ax )
+                
+        % Plot an ellipse in XY plane.
+        h = plot_ellipse_2d( obj, npoints, ax )
+        
+        % Generate 3D points on the ellipse fit.
+        p = get_ellipse_points( obj, npoints )
+
     end
     
     %% Private static methods: compute final properties value.
@@ -203,12 +213,6 @@ classdef epicell
         % Fit a 2D ellipse to a set of 3D points.
         [ f3d, v ] = fit_ellipse_3d( p, E, method )
         
-        % Plot a 2D ellipse in 3D.
-        h = plot_ellipse_3d( f3d, v, npoints )
-        
-        % Plot an ellipse in XY plane.
-        h = plot_ellipse_2d( f, npoints )
-        
     end
 end
 

src/@epicell/get_ellipse_points.m

+function p = get_ellipse_points( obj, npoints )
+%GET_ELLIPSE_POINTS Generate 3D points on the ellipse fit.
+    
+    f = obj.ellipse_fit;
+    v = epicell.euleurZXZ2rot( obj.euler_angles );
+    
+    x0      = f( 1 );
+    y0      = f( 2 );
+    z0      = f( 3 );
+    a       = f( 4 );
+    b       = f( 5 );
+    theta   = f( 6 );
+
+    R = [   cos( theta ) sin( theta ) ;
+        -sin( theta ) cos( theta ) ] ;
+    
+    t = linspace( 0.5 * pi, 2.5 * pi, npoints )';
+    XY0 = [ a * sin(t), b * cos(t) ];
+    XY1 = XY0 * R;
+    xr = XY1( :, 1 );
+    yr = XY1( :, 2 );
+    zr = zeros( numel( xr ), 1 );
+    pr = [ xr yr zr ];
+    
+    % Transform back
+    pb = pr * v';
+    xb = pb( :, 1 ) + x0;
+    yb = pb( :, 2 ) + y0;
+    zb = pb( :, 3 ) + z0;
+    
+    xb = [ xb ; xb(1,:) ];
+    yb = [ yb ; yb(1,:) ];
+    zb = [ zb ; zb(1,:) ];
+    
+    p = [ xb, yb, zb ];
+
+end
+

src/@epicell/plot_ellipse_2d.m

-function h = plot_ellipse_2d( f, npoints)
-%PLOT_ELLIPSE_2D Plot an ellipse in XY plane.
+function h = plot_ellipse_2d( obj, npoints, ax )
+%PLOT_ELLIPSE_2D Plot the ellipse projected on the XY plane.
 
-    if nargin < 2
-        npoints = 20;
-    end
+    p = get_ellipse_points( obj, npoints );
     
-    x0      = f(1);
-    y0      = f(2);
-    a       = f(3);
-    b       = f(4);
-    theta   = f(5);
+    xb = p( :, 1 );
+    yb = p( :, 2 );
     
-    R = [   cos( theta ) sin( theta ) ;
-        -sin( theta ) cos( theta ) ] ;
-    
-    t = linspace( 0 , 2 * pi, npoints )';
-    XY0 = [ a * sin(t), b * cos(t) ];
-    XY1 = XY0 * R;
-    xr = XY1( :, 1 ) + x0;
-    yr = XY1( :, 2 ) + y0;
-    
-    xr = [ xr ; xr(1,:) ];
-    yr = [ yr ; yr(1,:) ];
-    h = line( xr, yr );
+    xb = [ xb ; xb(1,:) ];
+    yb = [ yb ; yb(1,:) ];
+    h = line( ax, xb, yb );
 
 end
 

src/@epicell/plot_ellipse_3d.m

-function h = plot_ellipse_3d( f3d, v, npoints)
+function h = plot_ellipse_3d( obj, npoints, ax )
 %PLOT_ELLIPSE_3D Plot a 2D ellipse in 3D.
 
-    if nargin < 3
-        npoints = 20;
-    end
+    p = get_ellipse_points( obj, npoints );
     
-    x0      = f3d(1);
-    y0      = f3d(2);
-    z0      = f3d(3);
-    a       = f3d(4);
-    b       = f3d(5);
-    theta   = f3d(6);
-
-    R = [   cos( theta ) sin( theta ) ;
-        -sin( theta ) cos( theta ) ] ;
-    
-    t = linspace( 0 , 2 * pi, npoints )';
-    XY0 = [ a * sin(t), b * cos(t) ];
-    XY1 = XY0 * R;
-    xr = XY1( :, 1 );
-    yr = XY1( :, 2 );
-    zr = zeros( numel( xr ), 1 );
-    pr = [ xr yr zr ];
-    
-    % Transform back
-    pb = pr * v';
-    xb = pb( :, 1 ) + x0;
-    yb = pb( :, 2 ) + y0;
-    zb = pb( :, 3 ) + z0;
+    xb = p( :, 1 );
+    yb = p( :, 2 );
+    zb = p( :, 3 );
     
     xb = [ xb ; xb(1,:) ];
     yb = [ yb ; yb(1,:) ];
     zb = [ zb ; zb(1,:) ];
-    h = line( xb, yb, zb );
+    h = line( ax, xb, yb, zb );
 
 end