Bug or feature?

[Евгений Хорев]

When for existing path I do

path.segments[0].point = p0;
path.segments[0].handleOut = {angle: alpha, length: l};

it works as expected,
but when I do

path.segments[0].point = p0;
path.segments[0].handleOut.angle = alpha;
path.segments[0].handleOut.length = l;

it changes the handle’s direction to opposite for the same ‘alpha’ and ‘l’ values in some cases, totally unpredictable for me.
Is it bug or did I miss something?

[Jürg Lehni]

Could you please provide a case where the error happens, so we can look into it? Thanks!

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[Евгений Хорев]

Just checked one more time:

        connPath.segments[0].point = P0;
        //connPath.segments[0].handleOut = {
        //    angle: (Alpha - alpha0) * 180 / Math.PI + 90,
        //    length: l0
        //};
        connPath.segments[0].handleOut.angle = (Alpha - alpha0) * 180 / Math.PI + 90;
        connPath.segments[0].handleOut.length = l0;

Changing commented lines for last two ones makes it rotate vector to opposite direction for some values of it.
If it worth i could provide whole my code ~400 lines.

понедельник, 15 апреля 2013 г., 7:55:19 UTC+2 пользователь Jürg Lehni написал:

[Jürg Lehni]

Well we would simply need one path with coordinates where this happens.

[Евгений Хорев]

Sorry for the late reply!

Mentioned direction changes occurs with negative handle's values.

Didn't figured it out earlier because the drawing is preceded with nice chunk of trigonometry,

so the vector with a negative length and rotated by pi is the same vector.

And then this math, which captured all of my attention, is somehow friendshipped with paperjs library.

Anyway, here's a code snippet demonstrating difference in behavior:

http://jsfiddle.net/DMKWH/


вторник, 16 апреля 2013 г., 3:05:47 UTC+2 пользователь Jürg Lehni написал:

[Евгений Хорев]

Rose up to 0.9.4 and still there )

[Jürg Lehni]

After looking into this a bit more, I decided this is not actually a bug:


var point1 = new Point();
point1.angle = -45;
point1.length = -Math.sqrt(2);
// { x: -1, y: 1 }

var point2 = new Point(0, 0);
point2.length = -Math.sqrt(2);
point2.angle = -45;
// { x: 1, y: -1 }

Setting the length to negative values does not really make sense unless the vector already holds a value, in which case the effect is that it flips direction.

This is why in one version you don't see reversed vectors, and in the other you do.

If you make sure your length is never negative, this should not happen.

Best,

J

On Jun 22, 2013, at 10:22 , Евгений Хорев <khorev...@gmail.com> wrote:

> Rose up to 0.9.4 and still there )
>