Hi,   The problem I am currently having is that when I use the Surface command the image that I get is not correct. For some strange reason IDL seems to be confused and does not plot the surface correctly. The same problem occurs also when I use the iSurface tool in vector graphics mode. The surface that I want to plot is: x=sqrt(r^2+a^2) cos(phi)sin(theta) y=sqrt(r^2+a^2) sin(phi)sin(theta) z=r cos(theta) for r=8 and a=6. I can't really understand why the image is not correct in the right part of the plot. A part of my code can be seen below. pro testing ni=31 x=dblarr(ni,ni) y=dblarr(ni,ni) z=dblarr(ni,ni)   ;Theta->[0,180] degrees ;Phi-> [0,360] degrees theta=dindgen(ni)*(180.d0/(double(ni-1))) phi=dindgen(ni)*(360.d0/(double(ni-1)))   ;Convert to radians theta=theta*!dpi/(180.d0) phi=2.d0*phi*!dpi/(360.d0)   r=8 a=6 for j=0,ni-1 do begin   for i=0,ni-1 do begin     x[i,j]=sqrt(r^2+a^2)*cos(phi[i])*sin(theta[j])     y[i,j]=sqrt(r^2+a^2)*sin(phi[i])*sin(theta[j])     z[i,j]=r*cos(theta[j])   endfor endfor device,retain=2 Surface,z,x,y,/SAVE,$        xstyle=1,ystyle=1,xrange=[-11,11],yrange=[-11,11],$        zrange=[-11,11],zst=1,$        ax=30,az=-30,CHARSIZE=2.0,$        xtitle='!3x [G m/c!S!E2!R ]',ytitle='!3y [G m/c!S!E2!R ]',$        ztitle='!3z [G m/c!S!E2!R ]',/noerase end   Can I do the same thing using coordinate transformations and how?   Thank you in advance.   Kiki