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## Re: [Groff] Manuals in pdf format

 From: Miklos Somogyi Subject: Re: [Groff] Manuals in pdf format Date: Sat, 4 Mar 2006 15:38:48 +1100

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

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```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.
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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.)

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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
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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.
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But I am still not convinced that OpenGL's way is a good idea.
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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.
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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.
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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.

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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.
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Just the way you prepare your presentation slides: anything that distracts from the raison d'etre,
```must be out.

Miklos

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