"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Droj" <803### [at] drojde> wrote:
>
> Hi Oswald,
>
> I had some time to look at:
> https://www.frassek.org/3d-mathe/funktionsgraph-als-rohr-r%C3%B6hre/
>
> And I see where you're getting all of your code from, and I'm a bit disappointed
> that it isn't working "out of the box" like they seem to imply.
>
>
> While I'm happy I puzzled out some things to get the shape to look right, it's
> certainly not a general solution, which would be highly desirable.  I can
> envision using this to make text, offset curves, and generate signed distance
> functions for all manner of shapes.
>
> I would encourage you to keep working on this, and perhaps step through some
> larger values of u and render some representative frames such as are illustrated
> here:
>
>
https://image.jimcdn.com/app/cms/image/transf/dimension=301x1024:format=jpg/path/scee86bccd27a6ab2/image/idb0be97f034
4a
> 7c5/version/1573907965/konstruktion-des-funktionsgraphs-als-rohr-r%C3%B6hre.jpg
>
> Then it would be easier to see what is going wrong, and hopefully puzzle out
> why.
>
> It would be very nice indeed to be able to pass a function into a macro that
> would render a pipe/tube graph for that function.
>
> I would also keep in mind any differences in axis orientation, since it seems
> that their Y and Z axes are switched.
>
> - Bill

Hi Bill,

first of all thank you so much for encouraging me to follow up this matter and
for spending your time (may be wasting your time) to put me on the right track.

Well, I felt the same disappointment when I used the functions of B. Frassek's
page. I also tested the cardiode, the astroide and Archimeds spiral.
Same thing: flat tube in some parts!

I'm still looking for the air pump!

I spent some time to read what Wikipedia says about atan2 function.
Well, it gave me a nice headache but didn't clear the muddy waters.
The only thing I realised is that the function has to change depending on the
quadrants the graph passes.

BTW I used the macro:

#for (N, 0, tau, tau/180)
 #local X = FX (N);
 #local Y = FY (N);
 sphere {<X/4, Y/4, 0> 0.01 pigment {rgb y}}
 cylinder {0, x 0.05 pigment {rgb z} rotate z*degrees(PHI (N)) translate <X/4,
Y/4, 0>}
#end
but Povray at once complaint about 'undeclared tau'.
Can you give me a hint what that macro does? I am ignorant I know!

I promise to be persistant and as being a chemist I can be very persistant.

- Oswald

Post a reply to this message