[QT][QML][C++] Draw an interpolated polygon using C++ painter

[Pl45m4]

@Shadow-01

Something like spline interpolation?!

This example is for QChart but maybe you can use spline interpolation for your polygon.

• https://doc.qt.io/qt-5/qsplineseries.html

Wiki:
https://en.wikipedia.org/wiki/Spline_interpolation

[Shadow.01]

@mrjj Thanks; rounded polygon doesn't exist under the item that QT creator suggested me in the list of figure I can draw; should I import something special? Or, have you an example?

Thanks again for your time!

[Shadow.01]

@Pl45m4 Thanks but not; this is not the way; as told in my question, I already tried but it works only in a chart. And I should draw a free polygon outside a chart. Any other idea?

(No, SPline in a drawPolyline give an error; only under a chart I can use it).

[mrjj]

@Shadow-01 said in [QT][QML][C++] Draw an interpolated polygon using C++ painter:

thanks; rounded polygon doesn't exist under the item that QT creator suggested me in the list of figure I can draw; should I import something

Yes, the link has a that class in the bottom. ITs not a default Qt one.

The effect sounds like what you want.

but might end being too round. I have not tried it with a shape like yours.

[Shadow.01]

@mrjj Wait, for sure the line touch the edge? It seems not. It is Bezier algorythm? From the page, it seems so..

[Shadow.01]

@mrjj Thanks but for sure is not the way. My solution should absolutely touch the edge (given points), otherwise the line is not correct. Other solutions? Thanks for your time!

[mrjj]

@Shadow-01
Hi
but look at the airplane. it does touch the edges.
Outside of such rounded polygon im not sure what to use.

[Shadow.01]

No, unfortunately don't touch. If you see the internal vertical segment of each engine, is for sure longer in the left one. Anyway, thanks. :-(

[Pl45m4]

@Shadow-01 said in [QT][QML][C++] Draw an interpolated polygon using C++ painter:

(No, SPline in a drawPolyline give an error; only under a chart I can use it).

Read my answer again.
I know that you can't use QSplineSeries outside of QChart but you should take a took at it (spline interpolation) and the Wikipedia page, I linked.

If there's nothing like this in Qt you have to draw it yourself using mathematics.

[Shadow.01]

Thanks all so much. I found a solution, by using the Bezier Algorithm with a really small curve factor number. The result is almost the same as desired.

[mrjj]

@Shadow-01
You could show an image of the final result :) 🙄
So did you use code from link or did you make some yourself ?