hello, I have another Bezier question.
I'm splitting a bezier curve with ON_BezierCurve::Split, and I get two
pieces. Lets call them first and rest. Then I need to split "first"
again into first1, first2. Is it possible to join first2 and rest into
one bezier curve? there shouldnt be any problems mathematically since
they were originally attached as one curve.
there exists a function to create a ON_BezierCurve from an existing
ON_BezierCurve, but i dont think thats what I want.
thanks,
chris
On 07/11/2012 01:26 AM, phoenix wrote:
Hi, Chris!
> i have a few questions regarding working with ON_BezierCurves. I
want to
> evaluate the tangents at the start and end points of a bezier curve.
the
> function ON_BezierCurve::TangentAt() seems to be what i want, but it
> takes a double as its argument instead of a point. what does the double
> represent? distance from the beginning of the curve? how can i get the
> tangent at the beginning/end points of the curve?
The input double is the parameter, I think. A Bezier curve is a
parametric curve. The parameter t is usually between 0 to 1. So for
the beginning point, you can set t = 0, while for the end point, you
can set t = 1. See: http://en.wikipedia.org/wiki/B%C3%A9zier_curve
> also, is it possible to access specific control points of an
> ON_BezierCurve? I'm mostly concerned with the first and last points of
> the curve. the ON_BezierCurve::PointAt() looks close, but again, it
> takes a double as its argument and i'm not sure what to do with it.
The control points are accessible. Just use the double *CV(int
cv_index) method to return the control point, or use the GetCV method.
The PointAt() method returns the evaluating result of parameter t.
For the first and last control points of the curve, you can use CV(0)
and CV(xx.CVCount() - 1). For evaluation results, you can maybe use
PointAt(0) and PointAt(1).
Cheers!
Wu
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