How to produce a volumetric plot of spherical volume

Hi!

I want to know how to produce a volume plot that appears spherical. An example of such a plot is seen in Figure 1 in this article: http://iopscience.iop.org/0004-637X/701/1/642/fulltext/

Here is a simple piece of example-code of what I have so far:

[theta,r,phi] = meshgrid(1:1:100, 1:2:180, 1:2:360);

vol = -r.^2 - theta./phi;

figure(1); sh1 = slice(theta,r,phi,vol,50,50,50); set(sh1,'edgecolor','none');

This figure shows the slices of the volume, but I want this volume to appear spherical... so I try:

figure(2); [x,y,z] = sph2cart(theta,phi,r); sh2 = slice(x,y,z,vol,50,50,50); set(sh2,'edgecolor','none');

This doesn't work... How can I achieve this? Any help will be appreciated!

Thanks