Re: [Groff] Manuals in pdf format

[Miklos Somogyi]

On 03/03/2006, at 9:35 PM, Tadziu Hoffmann wrote:

> > Now the beauty of the thing is, that when you rotate a body,
> > you rotate the normal vectors as well.  When you translate
> > or scale, you translate and scale the vertices, but not
> > the normals.  Now these "Whew!" guys transform the normals,
> > always.
>
> If you scale the body anisotropically, you *have* to transform
> the normals, otherwise they wouldn't be normal anymore.  (And
> you have to transform them differently from how you transform
> the vertices, that's what they're saying. Think covariant and
> contravariant vectors.)

You are right, Tadziu. It never occurred to me to do anisotropic scaling
in the middle of things.
When I had a job like that, e.g. when showing velocity
distributions, I did all the anisotropic stuff at the beginning of the 
program, only once,
calculated normals, only once, then I could rotate, translate, 
iso-scale without re-calculating anything.
But, yes, one can not exclude the possibility of anisotropic scaling 
whilst in a viewing cycle.

But I am still not convinced that OpenGL's way is a good idea.
I don't deny that anisotropic jobs exist, just I think that, compared 
to not-to-distort physical objects, there aren't
too many. OpenGL's approach penalizes the vast majority of cases to 
accommodate the rare, when it is so easy
to fix the rare. And fix the rare with probably less work than what 
OpenGL's solution requires them to do.

Well, just my two cents. Anyway, all this was just an example (an 
exaggeration, as Werner pointed out), to
illustrate that by numbering i, ii, iii, 1, 2, 3 .. we create a problem 
that we have to fix. We talk a lot about
it, some applications do fix it, some don't, etc.
Doing i, ii, iii, 4, 5, 6 ... or 1, 2, 3, 4, 5, 6 ... would not crete a 
problem that we would need to solve.
And so far nobody came up with a convincing argument as to what 
advantages does the i, ii, iii, 1, 2, ...
system confers on the reader that would warrant the extra talking, the 
extra effort, the watching of whether
this or that application solves the problem or not.

Not as if this is huge problem, just that I believe that readers should 
not be distracted from their
searches/reading with page numbering  considerations.
Just the way you prepare your presentation slides: anything that 
distracts from the raison d'etre,
must be out.

Miklos