Answered
Hi - I have a parametric curve
C=Curve(t, t^3, t, -5, 5)And I have a movable point A attached to the curve C.
A=Point(C)
I would like to get the parameter t as I move A along the curve with the mouse. I don't know how to do this.
If I use
PathParameter(A)then I get a parameter value between 0 and 1, i.e. not the original parameterization of the curve.
If I try to use sliders, then the point A is no longer movable along the curve with the mouse.
The same question 
t=x(A)
To get the path parameter from t, you need a linear mapping of the interval [-5; 5] to the interval [0; 1]:
PathParameter = (t - (- 5)) / 10.
To get t from PathParameter, use
t=10*PathParameter - 5.
Thanks, but I would like a method which will work for any parametric curve, not just this simple one, eg.
If you attach a point A to the curve C, and then input
the parameter u will change with constant speed as A moves along C with constant speed. But I want the original parameter t. I don't know how to get it without numerically solving the transcendental equation for t in terms of x. This is sad, because the original parameterization of the curve C has been ruthlessly "forgotten". It could have been kept as auxiliary data in the storage of C, but it seemingly wasn't.TYou can use natural parameter
s=Length(C, C(0), A)
have you tried to move A point on curve C created by a slider a
Parametric curve describes the motion along a geometric curve. When you see the trace of skis on the snow there is no way to retrieve the speed of the skier.
Bruce, finaly I understand what you mean.
1. curve c(t)
2. slider
3. A=c(t)
Try this move_me.ggb
Thank you! So - I need to make a slider and then set A=C(t). I was doing it wrong, I was attaching A to C via the "Point on Object" tool, which wasn't a good method.
3. A=c(slider)
In fact this is my attached in my last post
really pathparameter() for curve(t) t from 0 to k is equal to t/k
Comments have been locked on this page!