"Mike Williams" <mik### [at] nospamplease> ha scritto nel messaggio
news:L7D### [at] econymdemoncouk...
> Those aren't parametric equations. They're straight forward polar
> equations.

They are parametric functions. Instead of having a F(x,y,z), with orbitals
is *easier* to work with polar coordinates ==> F(r,theta,phi)

> You haven't told us what "r" is.

Aw, come on. Don't you know polar coordinates? :P

> >The parametric equations are (obviously):
> >x = r*sin(theta)*sin(phi);
> >y = r*sin(theta)*cos(phi);
> >z = r*cos(theta);

> These are parametric equations, but they're just the parametric
> equations of a sphere, which doesn't help very much.

No. R is a parameter, just like theta and phi. It's not a fixed value. You
need those equations to convert polar coordinates to Cartesian coordinates.

> To convert that into a POV function we need to:-
>         Change the "pow"s into "^"s

Huh, doesn't pow() work with isos?

>         Change theta and pii into f_th(x,y,z) and f_ph(x,y,z)

Ok.

>         Think of a value for "r" (I chose 1.0)

Nope. R is the third polar coordinate, it can't be a fixed value.
You have a point in 3d space defined by three Cartesian coordinates <X,Y,Z>.
If you're using polar coordinates your point is known if you know its three
polar coordinates <r,theta,phi>.
r is the length of the vector <x,y,z>. theta is the angle between that
vector and the Z axis. phi is the angle between the projected vector on the
XY plane and the Y axis.

>         Assume that "sen" is a misprint for "sin"

Oops. No, it's just Italian.

--
Jonathan.

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