David Given wrote:

> ...which demonstrates what you can do with isosurfaces. Alas, I haven't
> found source for that one...)

I made a less impressive cityscape here:

http://news.povray.org/povray.binaries.images/thread/%3C4a358a3b@news.povray.org%3E/?ttop=341111&toff=300

I wasn't too happy with it but the height function is just:

#local f_cells = function {pattern {cells}}

#local f_base  = function {pattern {hexagon rotate 90*x scale 0.005 
turbulence 0.5}}

#local f_scape = function(x,y,z)
{
   0.6* f_cells(x*30,y*30,z*30) *
   select( f_base(x,y,z)-0.2, 0, 1.0)
}

The scene used a height_field but an isosurface should also work.

The windows are just texture (using slope pattern you can give
different textures to vertical walls).

> For example, if I replacing the sin(x) with mod(x, 2)-1 then I get the
> same result... but now I only get half the balls, and those balls have
> in turn been halved. Given that mod(x, 2)-1 and sin(x) both return
> values in the domain [-1..1] I'm slightly confused by this.

The problem with mod is that returns negative fractions for
negative numbers so your expression actually returns values
in the domain [-3,-1] for negative x. That's why half of the
balls are missing. You can use abs(mod(x,2))-1.

But I didn't see the ball halving problem. Note that the
lower part of the spheres was missing in my example due to
the contained_by clipping at the y=0 plane.

Also I shied away from using mod because it has undefined
gradient at the boundaries that may or may not be a problem
for the isosurface rendering later. Of course, it probably
evaluates faster than sin.

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