th=pi/4;
f=@(x,y,z)(x*sin(th)+y*cos(th)-1).^2+(x*cos(th)-y*sin(th)+1).^2+z.^2-50;
g=@(x,y,z)x*(cos(th)+sin(th))+y*(sin(th)-cos(th))+0*z;
h=implicitmesh(f,[-pi pi],[-200 200],[-8 8],50);
set(h,'AmbientStrength',.5);%¿ÉÒÔÉèÖø÷ÖÖЧ¹û
hold on%¿ÉÒÔÌí¼ÓͼÐÎ
h=implicitmesh(g,[-pi pi],[-200 200],[-8 8]);
colormap hsv;set(h,'AmbientStrength',.8,'FaceAlpha',.5);%¿ÉÒÔÉèÖø÷ÖÖЧ¹û
axis off;axis equal;shading interp;camlight;lighting gouraud;

implicitmeshµÄ´úÂë
function h=implicitmesh(f,xlimit,ylimit,zlimit,gd)
%implicitmesh(f,span,gd):»­Òþº¯ÊýÇúÃæf(x,y,z)=0µÄÍø¸ñͼ,
%                          ¸÷×ø±ê·¶Î§¾ùÏÞ¶¨ÔÚspan=[lb,ub],
%                          Íø¸ñÊýΪgd£¬Ä¬ÈÏΪ25
%implicitmesh(f,xspan,yspan,zspan,gd):»­Òþº¯ÊýÇúÃæf(x,y,z)=0,
%                          ¸÷×ø±ê·¶Î§·Ö±ðÏÞ¶¨ÔÚxspan,yspan,zspan
%h=implicitmesh(...)£º»­Òþº¯ÊýÇúÃæ²¢Êä³ö¾ä±ú
%ÀýÒ»£º
%implicitmesh(inline('x.*y+z.^2'),[-5 5])%×¢Òâ*\^Ò»¶¨ÒªÉè³ÉµãÔËËã
%Àý¶þ£º
%f=@(x,y,z)x.^2+y.^2+0*z-1;%×¢ÒâÈç¹ûfÖв»º¬Ä³¸ö±äÁ¿Ò»¶¨Òª¼ÓÉÏÖîÈç0*yµÄÏî¡£
%implicitmesh(f,[-1 1],10)
%ÀýÈý£º
%f=@(x,y,z)(x.^2 + (9/4)*y.^2 + z.^2 - 1).^3 - x.^2.*z.^3 - (9/80)*y.^2.*z.^3;
%g=@(x,y,z)(sqrt(x.^2+y.^2)-2).^2+z.^2-.09;
%implicitmesh(f,[-1.5 1.5],[-.8 .8],[-1.5 1.5],50);
%hold on%¿ÉÒÔÌí¼ÓͼÐÎ
%h=implicitmesh(g,[-2.3,2.3]);
%colormap hsv;set(h,'facecolor','none');%¿ÉÒÔÉèÖø÷ÖÖЧ¹û
%axis off;axis equal;
if nargin==2
    ylimit=xlimit;zlimit=xlimit;gd=25;
elseif nargin==3
    gd=ylimit;ylimit=xlimit;zlimit=xlimit;
elseif nargin==4
    gd=25;
elseif nargin==5
else
    error('Error in input arguments')
end
x=linspace(xlimit(1),xlimit(2),gd);
y=linspace(ylimit(1),ylimit(2),gd);
z=linspace(zlimit(1),zlimit(2),gd);
[x,y,z]=meshgrid(x,y,z);val=f(x,y,z);
[f,v]=isosurface(x,y,z,val,0);
if isempty(f)
    warning('There is no graph in the range.');
    p=[];
else
    newplot;
    p=patch('Faces',f,'Vertices',v,'CData',v(:,3),'facecolor','w','EdgeColor','flat');
    isonormals(x,y,z,val,p);view(3);grid on
end
if nargout==0
else
    h=p;
end