I can think of a couple ways of doing this. For a general purpose approach I’d create a distance field from your mesh surface, then cross the gradient of that with a noise gradient. At lower frequencies will look pretty close to your reference.
Here’s what a FieldTrip graph for that would look like:
Otherwise, if you need it to be a bit more specific to your mesh, or don’t want to have to convert your mesh to a volume first you could probably create a couple of spline paths inside your mesh and project those radially on to the surface (use front culling rather then back culling). Like a bunch of 1px viewports.
Hope that helps for some ideas. Can pack up that patch if you want it.