javascript - Paperjs metaballs 不工作/显示

Question

我正在尝试自定义来自 Paperjs ( http://paperjs.org/examples/meta-balls/ ) 的 metaballs 示例。问题是，即使复制粘贴它也行不通。它不绘制/显示球之间的“桥梁”。

这是一个 jsFiddle:http://jsfiddle.net/AK47p/

代码如下:

$(document).ready(function () {

    // Get a reference to the canvas object
    var canvas = document.getElementById('canvas');
    // Create an empty project and a view for the canvas:
    paper.setup(canvas);
    // Create a simple drawing tool:
    var tool = new paper.Tool();

    // Ported from original Metaball script by SATO Hiroyuki
    // http://park12.wakwak.com/~shp/lc/et/en_aics_script.html
    paper.project.currentStyle = {
        fillColor: 'black'
    };

    var ballPositions = [[255, 129], [610, 73], [486, 163],
        [117, 259], [484, 326], [843, 306], [789, 215], [949, 82],
        [292, 128], [917, 233], [352, 86], [92, 98]];

    var handle_len_rate = 2.4;
    var circlePaths = [];
    var radius = 50;
    for (var i = 0, l = ballPositions.length; i < l; i++) {
        var circlePath = new paper.Path.Circle({
            center: ballPositions[i],
            radius: 50
        });
        circlePaths.push(circlePath);
    }

    var largeCircle = new paper.Path.Circle({
        center: paper.view.center,
        radius: 100,
        fillColor: 'green'
    });
    circlePaths.push(largeCircle);

    tool.onMouseMove = function(event) {
        largeCircle.position = event.point;
        generateConnections(circlePaths);
    }

    var connections = new paper.Group(); var thePath;
    function generateConnections(paths) {
        // Remove the last connection paths:
        connections.children = [];

        for (var i = 0, l = paths.length; i < l; i++) {
            for (var j = i - 1; j >= 0; j--) {
                var path = metaball(paths[i], paths[j], 0.5, handle_len_rate, 300);thePath = path;
                if (path) {
                    connections.appendTop(path);
                    path.removeOnMove();
                }
            }
        }
    }

    generateConnections(circlePaths);

    // ---------------------------------------------
    function metaball(ball1, ball2, v, handle_len_rate, maxDistance) {
        var center1 = ball1.position;
        var center2 = ball2.position;
        var radius1 = ball1.bounds.width / 2;
        var radius2 = ball2.bounds.width / 2;
        var pi2 = Math.PI / 2;
        var d = center1.getDistance(center2);
        var u1, u2;

        if (radius1 == 0 || radius2 == 0)
            return;

        if (d > maxDistance || d <= Math.abs(radius1 - radius2)) {
            return;
        } else if (d < radius1 + radius2) { // case circles are overlapping
            u1 = Math.acos((radius1 * radius1 + d * d - radius2 * radius2) /
                    (2 * radius1 * d));
            u2 = Math.acos((radius2 * radius2 + d * d - radius1 * radius1) /
                    (2 * radius2 * d));
        } else {
            u1 = 0;
            u2 = 0;
        }

        var angle1 = center2.subtract(center1).getAngleInRadians();
        var angle2 = Math.acos((radius1 - radius2) / d);
        var angle1a = angle1 + u1 + (angle2 - u1) * v;
        var angle1b = angle1 - u1 - (angle2 - u1) * v;
        var angle2a = angle1 + Math.PI - u2 - (Math.PI - u2 - angle2) * v;
        var angle2b = angle1 - Math.PI + u2 + (Math.PI - u2 - angle2) * v;
        var p1a = center1 + getVector(angle1a, radius1);
        var p1b = center1 + getVector(angle1b, radius1);
        var p2a = center2 + getVector(angle2a, radius2);
        var p2b = center2 + getVector(angle2b, radius2);

        // define handle length by the distance between
        // both ends of the curve to draw
        var totalRadius = (radius1 + radius2);
        var d2 = Math.min(v * handle_len_rate, (p1a - p2a).length / totalRadius);

        // case circles are overlapping:
        d2 *= Math.min(1, d * 2 / (radius1 + radius2));

        radius1 *= d2;
        radius2 *= d2;

        var path = new paper.Path({
            segments: [p1a, p2a, p2b, p1b],
            style: ball1.style,
            closed: true
        });
        var segments = path.segments;
        segments[0].handleOut = getVector(angle1a - pi2, radius1);
        segments[1].handleIn = getVector(angle2a + pi2, radius2);
        segments[2].handleOut = getVector(angle2b - pi2, radius2);
        segments[3].handleIn = getVector(angle1b + pi2, radius1);
        return path;
    }

    // ------------------------------------------------
    function getVector(radians, length) {
        return new paper.Point({
            // Convert radians to degrees:
            angle: radians * 180 / Math.PI,
            length: length
        });
    }
});

如您所见，我将代码封装在一个 domReady 函数中，因为这将成为幻灯片的一部分。我按照此处的说明 (http://paperjs.org/tutorials/getting-started/using-javascript-directly/) 执行此操作。知道有什么问题吗？我检查了一遍又一遍，我一定是遗漏了什么……

谢谢

Answer 1

找出丢失的东西。它在 Paperjs 上没有很好的文档记录，无论如何，如果您像常规 javascript 一样使用它，请确保对纸张对象(Point、Path 等)的所有操作都表示为方法，而不是运算符。

错误

var d2 = Math.min(v * handle_len_rate, (point1a - point2a).length / totalRadius);

右

var d2 = Math.min(v * handle_len_rate, point1a.subtract(point2a).length / totalRadius);