Unsolved Getting coefficients for PathCubic?
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Hi,
I would like to compute dependent variable based on independent variable from cubic polynomial which is basically PathCubic.
I would be grateful if someone could tell me, where do I get coefficients from PathCubic ?Big thanks,
Mateusz -
Hi! There is no public interface other than that described in the manual: PathCubic QML Element.
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Ok, so it's only to move control points with mouse but no way to know the function or get x/y values at any given point ?
I found this https://doc-snapshots.qt.io/qt5-dev/qml-qtquick-pathinterpolator.html
But unfortunately it's progress not x value this takes as an argument and even then fitting a cubic polynomial again just to get coefficients, would be wired.I hope they fix that...
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Of course it takes a "progress" and not an x value; the curve is parameterized along its local normalized coordinate t. Also, tbh, I don't see what you want to get fixed there, it's f(t) -> (x, y). Just give the path interpolator said progress value and read its x and y properties.
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I would like to get cubic polynomial coefficients of PathCubic, if possible. That would be really helpeful and usueful.
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@Mateusz said in Getting coefficients for PathCubic?:
I would like to get cubic polynomial coefficients of PathCubic, if possible. That would be really helpeful and usueful.
I think you're missing the point. The polynomial is given as a parametric curve
f(t) = {x, y}
, and not as the scalar functiony = y(x)
, just as @Wieland wrote. So, no, you can't know whaty
corresponds to whichx
unless you know the exact way the curve was parametrized. -
Ah right, its Beizer curve not simple polynomial.
In my case I want to set control points both with mouse and with SpinBox to see exact values and let user to type exact values.
Thanks