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Draw a dash CurveTo
by ericlin


In the previous session, we have discussed the similarity between Bezier curve to and the "throwing ball" curve.

However, both equations of Bezier curve and the Parabolic curve are functions of time t; If we apply this formula to draw a dash, then the segment of dash will variable in length. Short, when the ball flys slow and long when the ball falls fast.

How to calculate the time so that the length of travel is nearly uniform ?

I dont know.

Here is an approximation policy.

If the segment is short, we assume that, the initial speed is nearly the same as the end speed for each segment. Then we assume the ball is travelling in a uniform speed during this segment. So, the time need to travel a segment length of 10 pixel is about

t=10/Math.sqrt(vx*vx+vy*vy);

Thus, we can plot a "not bad" dash curve.

The equation to plot a curve between t1 and t2 can be calculate either by Bezier curve or by the formula that I discussed in previous session.

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