Rotation around center of mass is weird.

Chazrox

Im drawing a star and trying to rotate it around its center of mass without including the gradient in the rotation. At lower point counts its alot more obvious whats going on. For some reason at higher point counts its stable. hmmmm

If anyone else wants to give it a go.. Thank you!

MyKnobLaf.registerFunction("drawRotarySlider", function(g, obj)
{
    var a = obj.area;
    var range = obj.max - obj.min;
    var stableSize = a[2] * (1.0 - 2.0 * 0.15);
    var ox = a[0] + (a[2] - stableSize) / 2;
    var oy = a[1] + (a[2] - stableSize) / 2;
    var cx = ox + stableSize / 2;
    var cy = oy + stableSize / 2;
    var sw = stableSize / 200.0;
    var startOffset = 2.5;
    var totalSweep = 2.0 * startOffset;
    var endOffset = -startOffset + totalSweep * (obj.value - obj.min) / range;

    // ============ COLOUR CONTROL ============
    // -- Star Body 3 --
    var cStarBody3Top = 0xff888888;
    var cStarBody3Bot = 0xff333333;

    // -- starBody3 --
    var starBody3Size = stableSize * 0.8;
    var starBody3Star = Content.createPath();
    starBody3Star.addStar(
        [0.5, 0.5],
        3,
        0.42,
        0.5,
        endOffset
    );
    starBody3Star.roundCorners(1);
    var starBody3Area = [cx - starBody3Size * 0.5, cy - starBody3Size * 0.5, starBody3Size, starBody3Size];
    g.setGradientFill([cStarBody3Top, cx, cy - starBody3Size * 0.5 + starBody3Size * 0.5 - starBody3Size * 0.5, cStarBody3Bot, cx, cy + starBody3Size * 0.5 + starBody3Size * 0.5 - starBody3Size * 0.5, false]);
    g.fillPath(starBody3Star, starBody3Area);

});

I Cant figure out why the shape warbles when

ustk

@Chazrox you need to use starBody3Star.getBounds(multiplier) as drawing area. Complex shapes manage their own area, that is dynamic so it can hold the entire shape without being distorted.
A star doesn't fit in the same square as you rotate it. It needs to grow, shrink, and translate dynamically.
In your code you force it to draw in a fix square, so the shape adapts...

ustk

@Chazrox

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ustk

@Chazrox It's even more obvious with 3 branches:

I love this one because it reminds me of the Wankel engine

Rotation around center of mass is weird.

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