function?[pellipse]=phantom3d（varargin）

%PHANTOM3D?Three-dimensional?analogue?of?MATLAB?Shepp-Logan?phantom
%???P?=?PHANTOM3D（DEFN）?generates?a?3D?head?phantom?that?can???
%???be?used?to?test?3-D?reconstruction?algorithms.
%
%???DEF?is?a?string?that?specifies?the?type?of?head?phantom?to?generate.
%???Valid?values?are:?
%?????????
%??????‘Shepp-Logan‘????????????A?test?image?used?widely?by?researchers?in
%???????????????????????????????tomography
%??????‘Modified?Shepp-Logan‘???（default）?A?variant?of?the?Shepp-Logan?phantom
%???????????????????????????????in?which?the?contrast?is?improved?for?better??
%???????????????????????????????visual?perception.
%
%???N?is?a?scalar?that?specifies?the?grid?size?of?P.
%???If?you?omit?the?argument?N?defaults?to?64.
%?
%???P?=?PHANTOM3D（EN）?generates?a?user-defined?phantom?where?each?row
%???of?the?matrix?E?specifies?an?ellipsoid?in?the?image.??E?has?ten?columns
%???with?each?column?containing?a?different?parameter?for?the?ellipsoids:
%???
%?????Column?1:??A??????the?additive?intensity?value?of?the?ellipsoid
%?????Column?2:??a??????the?length?of?the?x?semi-axis?of?the?ellipsoid?
%?????Column?3:??b??????the?length?of?the?y?semi-axis?of?the?ellipsoid
%?????Column?4:??c??????the?length?of?the?z?semi-axis?of?the?ellipsoid
%?????Column?5:??x0?????the?x-coordinate?of?the?center?of?the?ellipsoid
%?????Column?6:??y0?????the?y-coordinate?of?the?center?of?the?ellipsoid
%?????Column?7:??z0?????the?z-coordinate?of?the?center?of?the?ellipsoid
%?????Column?8:??phi????phi?Euler?angle?（in?degrees）?（rotation?about?z-axis）
%?????Column?9:??theta??theta?Euler?angle?（in?degrees）?（rotation?about?x-axis）
%?????Column?10:?psi????psi?Euler?angle?（in?degrees）?（rotation?about?z-axis）
%
%???For?purposes?of?generating?the?phantom?the?domains?for?the?x-?y-?and?
%???z-axes?span?[-11].??Columns?2?through?7?must?be?specified?in?terms
%???of?this?range.
%
%???[PE]?=?PHANTOM3D（...）?returns?the?matrix?E?used?to?generate?the?phantom.
%
%???Class?Support
%???-------------
%???All?inputs?must?be?of?class?double.??All?outputs?are?of?class?double.
%
%???Remarks
%???-------
%???For?any?given?voxel?in?the?output?image?the?voxel‘s?value?is?equal?to?the
%???sum?of?the?additive?intensity?values?of?all?ellipsoids?that?the?voxel?is?a?
%???part?of.??If?a?voxel?is?not?part?of?any?ellipsoid?its?value?is?0.??
%
%???The?additive?intensity?value?A?for?an?ellipsoid?can?be?positive?or?negative;
%???if?it?is?negative?the?ellipsoid?will?be?darker?than?the?surrounding?pixels.
%???Note?that?depending?on?the?values?of?A?some?voxels?may?have?values?outside
%???the?range?[01].
%????
%???Example
%???-------
%????????ph?=?phantom3d（128）;
%????????figure?imshow（squeeze（ph（64::）））
%
%???Copyright?2005?Matthias?Christian?Schabel?（matthias?@?stanfordalumni?.?org）
%???University?of?Utah?Department?of?Radiology
%???Utah?Center?for?Advanced?Imaging?Research
%???729?Arapeen?Drive
%???Salt?Lake?City?