Jean-Pierre,

Nice work!

I have not had a recent experience with any drawing graphic editor so I
can't help you with that. But certainly you will find suggestions on that
from the forum people.

I have just scratched your airplane code. And I have a few comments about
the evaluation conclusions about OpenSCAD in your referred site. As I
barely read french, I based my comments on a Google translation of them to
english.

First of all, hull() is not a linear interpolation of two shapes. It is the
minimal convex shape that includes all the shapes. The technical name of
that operation is convex hull https://en.wikipedia.org/wiki/Convex_hull.
That means that hull() is unable to produce holed shapes because its result
is always convex. There is no primitive operation in OpenSCAD that provides
a linear interpolation of two shapes.

Second, functions may be much more complex than a simple algebraic
expression as you suggest. Thanks to list comprehension and conditional
expressions, you can code iterations, recursions, tests and
pre-calculations inside a function. Here is a simple example that uses your
formule_Bezier() function:

// evaluates the points in a Bezier curve for a given list of parameter
values.
// if t is a list of numbers returns a list of points
// if t is a number returns a point

// ctl_pts should be a path, that is a list of pts with the same dimension

function Bezier_curve_sample(ctl_pts, t) =
is_num(t)
? formule_Bezier(t, ctl_pts)
: [for(ti=t)  formule_Bezier (ti, ctl_pts)] ;

To get a display of the curve we may use a module similar to your Bezier()
module:

// draws a polygonal through pts

module line(pts,width) {

for(i=[0:len(pts)-2])

  hull() {

    translate(pts[i])   sphere(width);

    translate(pts[i+1]) sphere(width);

  }

}

// 2D curve example

pts = [ [0,0], [10,5], [20,-2], 30,20]];

curve = Bezier_curve_sample(pts, [for(i=[0:20]) i/20]);

polygon( curve );

color("red") line( curve, .3);

echo( curve = curve );

Note that above I don't call formule_Bezier() at each individual coordinate
as you do because OpenSCAD is not a typed language and the expression
inside is valid for both numerical control values and vector control
points. It is valid even for matricial control points, that is lists of
vector control points and suitable to sample Bezier Patches!

Finally, you mention the miss of a C-like break in OpenSCAD language. There
are many ways to deal with the need of premature interruptions in a
sequence of computations in OpenSCAD. Breaks are unavoidable in recursion,
an invaluable language tool. Here is an example:

// computes the list of Fibonacci numbers up to a limiting value greater
than 0
function Fibonacci(limit, _result) =
is_undef(_result)
? Fibonacci(limit,[0,1])
: let( n = len(_result) )
_result[n-1]+_result[n-2] > limit
? _result
: Fibonacci(limit, concat(_result, _result[n-1]+_result[n-2] ) );

Besides recursion, you have C-like for as a tool that can interrupt
iterations. A break() clause is not the only way to interrupt iterations.

Jean-Pierre Rousset loupapetjpr@gmail.com wrote:

Very happy to know that you were interested. Thank you.

Data entry was a bit tedious for modeling half of the plane since it is
symmetrical. But, for the interpolation squares to be the least visible
possible, it was necessary to enter the ribs and especially the frames for
the fuselage.
How to do it the easiest ?... I don't have a "CATIA" type software to
generate mathematically perfect shapes.
Personally, I do not master the spoken English language, I understand it by
reading, and I do not hesitate to use "Google Translate" which I sometimes
correct otherwise I would do nothing. It is not a dishonor to ignore a
language ! ...

Regarding the Renault FT tank, you are right ! ..

Today's manufacturers are especially interested in this kind of vehicle,
SUVs, "ox cart" in French "char à bœufs" that I find very ugly and very
old-fashioned, invented before the war ! ...
For everyone to his own tastes ! ...
There are too many unnecessary things in a car, which is why I prefer real
old vehicles without digital. They have a soul that I can't find now.

Greetings,
under a beautiful sun of Cannes / Nice

Le jeu. 28 janv. 2021 à 15:11, trygve@totallytrygve.com a écrit :

--

"Pourquoi faire simple quand on peut faire encore plus simple..." "Le plus
simple est de ne pas faire.....seulement si c'est possible !..."

On 1/28/2021 9:43 AM, Jean-Pierre Rousset wrote:

You do have OpenSCAD to generate mathematically perfect shapes.  You
have to supply your own math, or there are libraries available, but one
of the huge advantages of OpenSCAD is that if you can describe the shape
using math, you can model it.

There are too many unnecessary things in a car, which is why I prefer real
old vehicles without digital. They have a soul that I can't find now.

This is true for motorcycles as well.  I have a newer (2015) BMW F800GS
that didn't run right for 5 years because of a sensor glitch in the
electronic ignition intake manifold that has another name.
While that was in the shop for a year I bought a 1988 'Bumblebee' R100GS.
Technically it's an inferior bike so why do I love it more?
I can fix it, that's why.  And it has soul.

OpenSCAD mailing list

Jean-Pierre Rousset loupapetjpr@gmail.com

A Bézier curve / vector drawing program might work well.
Inkscape is the free/opensource option (if you're on Mac OS X/Linux you could try Cenon), or for ChromeOS GraviT.
An affordable commercial option is Serif's Affinity Designer available for Mac OS X and Windows.
A programmatic option is METAPOST (or see Processing or Nodebox, though I had precision issues when I tried to use them for CAM).
William

On the subject of bezier's, I implemented them in my own libraries with:

function linearBezier(p0, p1, t) = p0 + (p1 - p0) * t;

where all 3 functions take an argument t which is between 0 and 1, the
fraction of the path along the curve.
linearBezier (only named that for consistency, and I thought it was funny)
finds a linear interpretation between two points,  quadraticBezier finds
the point along the parabolic segment defined by the 3 points, and
cubicBezier (the one normally used in most graphical applications) finds
the point along the cubic curve defined by the 4 points.

On Thu, Jan 28, 2021 at 6:49 PM Lou_Papet loupapetjpr@gmail.com wrote: