// http://www.emanueleferonato.com/2011/08/05/slicing-splitting-and-cutting-objects-with-box2d-part-4-using-real-graphics/
const EPSILON = 0.1;
const POINT_SQR_EPSILON = 5;
function compare(a, b) {
if (a.fraction > b.fraction) {
return 1;
} else if (a.fraction < b.fraction) {
return -1;
}
return 0;
}
function equals (a, b, epsilon) {
epsilon = epsilon === undefined ? EPSILON : epsilon;
return Math.abs(a-b) < epsilon;
}
function equalsVec2(a,b, epsilon) {
return equals(a.x, b.x, epsilon) && equals(a.y, b.y, epsilon);
}
//Intersection 辅助类，用于测试形状与形状是否相交. pointLineDistance 计算点到直线的距离。
//计算点到直线的距离。如果这是一条线段并且垂足不在线段内，则会计算点到线段端点的距离。
function pointInLine (point, a, b) {
return cc.Intersection.pointLineDistance(point, a, b, true) < 1;
}
cc.Class({
extends: cc.Component,
//碰撞检测
onEnable: function () {
this.debugDrawFlags = cc.director.getPhysicsManager().debugDrawFlags;//开启物理系统
//指定物理系统需要绘制哪些调试信息
//绘制关节链接信息
//绘制形状
cc.director.getPhysicsManager().debugDrawFlags =
cc.PhysicsManager.DrawBits.e_jointBit |
cc.PhysicsManager.DrawBits.e_shapeBit
;
//cc.log("cutting-objects:onEnable");
},
onDisable: function () {
cc.director.getPhysicsManager().debugDrawFlags = this.debugDrawFlags;
//cc.log("cutting-objects:onDisable");
},
// use this for initialization
onLoad: function () {
var canvas = cc.find('Canvas');
//触摸监听
canvas.on(cc.Node.EventType.TOUCH_START, this.onTouchStart, this);
canvas.on(cc.Node.EventType.TOUCH_END, this.onTouchEnd, this);
canvas.on(cc.Node.EventType.TOUCH_MOVE, this.onTouchMove, this);
//线
this.ctx = this.getComponent(cc.Graphics);
},
onTouchStart: function (event) {
//cc.log("cutting-objects:onTouchStart");
this.touching = true;
this.r1 = this.r2 = this.results = null;
this.touchStartPoint = this.touchPoint = cc.v2( event.touch.getLocation() );
},
onTouchMove: function (event) {
//cc.log("cutting-objects:onTouchMove");
this.touchPoint = cc.v2( event.touch.getLocation() );
},
onTouchEnd: function (event) {
//cc.log("cutting-objects:onTouchEnd");
this.touchPoint = cc.v2( event.touch.getLocation() );
this.recalcResults();
this.touching = false;
let point = cc.v2( event.touch.getLocation() );
if ( equals(this.touchStartPoint.sub(point).magSqr(), 0) ) return;
// fraction 射线与碰撞体相交的点占射线长度的分数
// recalculate fraction, make fraction from one direction
this.r2.forEach(r => {
r.fraction = 1 - r.fraction;
});
//results 是 射线碰撞 矩阵
let results = this.results;
let pairs = [];
cc.log("results.length:"+results.length);
for (let i = 0; i < results.length; i++) {
let find = false;
let result = results[i];
cc.log("pairs.length:"+pairs.length);
for (let j = 0; j < pairs.length; j++) {
let pair = pairs[j];
//碰撞体
cc.log("pair[0]||result.collider||pair[0].collider:"+pair[0]+","+result.collider.name+","+pair[0].collider.name);
if (pair[0] && result.collider === pair[0].collider) {
find = true;
// one collider may contains several fixtures, so raycast may through the inner fixture side
// we need remove them from the result
let r = pair.find((r) => {
return r.point.sub(result.point).magSqr() <= POINT_SQR_EPSILON;
});
if (r) {
pair.splice(pair.indexOf(r), 1);
}
else {
pair.push(result);
}
break;
}
}
if (!find) {
pairs.push([result]);
}
}
for (let i = 0; i < pairs.length; i++) {
let pair = pairs[i];
if (pair.length < 2) {
continue;
}
// sort pair with fraction
pair = pair.sort(compare);
let splitResults = [];
// first calculate all results, not split collider right now
for (let j = 0; j < (pair.length - 1); j +=2) {
let r1 = pair[j];
let r2 = pair[j+1];
if (r1 && r2) {
this.split(r1.collider, r1.point, r2.point, splitResults);
}
}
if (splitResults.length <= 0) {
continue;
}
let collider = pair[0].collider;
let maxPointsResult;
for (let j = 0; j < splitResults.length; j++) {
let splitResult = splitResults[j];
for (let k = 0; k < splitResult.length; k++) {
if (typeof splitResult[k] === 'number') {
splitResult[k] = collider.points[splitResult[k]];
}
}
if (!maxPointsResult || splitResult.length > maxPointsResult.length) {
maxPointsResult = splitResult;
}
}
if (maxPointsResult.length < 3) {
continue;
}
// keep max length points to origin collider
collider.points = maxPointsResult;
collider.apply();
let body = collider.body;
for (let j = 0; j < splitResults.length; j++) {
let splitResult = splitResults[j];
if (splitResult.length < 3) continue;
if (splitResult == maxPointsResult) continue;
// create new body
let node = new cc.Node();
node.position = body.getWorldPosition();
node.rotation = body.getWorldRotation();
node.parent = cc.director.getScene();
node.addComponent(cc.RigidBody);
let newCollider = node.addComponent(cc.PhysicsPolygonCollider);
newCollider.points = splitResult;
newCollider.apply();
}
}
},
//切割：碰撞体 点1 点2
split: function (collider, p1, p2, splitResults) {
//collider.body 碰撞体会在初始化时查找节点上是否存在刚体，如果查找成功则赋值到这个属性上
let body = collider.body; //碰撞盒 的 刚体 rigidbody
let points = collider.points; //碰撞盒 的 Vec2[] 多边形顶点数组
cc.log("split-1:"+collider.name+","+p1+","+p2+","+splitResults.length);
cc.log("split-2:"+body.type+","+points);
// The manager.rayCast() method returns points in world coordinates, so use the body.getLocalPoint() to convert them to local coordinates.
//将 p1 p2 转换成碰撞体的坐标系
p1 = body.getLocalPoint(p1);
p2 = body.getLocalPoint(p2);
//p1-p2 p2-p1
let newSplitResult1 = [p1, p2];
let newSplitResult2 = [p2, p1];
//
let index1, index2;
//遍历碰撞体的点，
for (let i = 0; i < points.length; i++) {
let pp1 = points[i];//当前顶点坐标 给 p1
let pp2 = i === points.length - 1 ? points[0] : points[i+1]; //如果i是最后一个，第一个坐标 给 p2，否则给下一个点坐标
//点p1 到 线段pp1-pp2 的距离；如果in1没赋值 && p1到线段有距离
if (index1 === undefined && pointInLine(p1, pp1, pp2)) { index1 = i; }
//点p2 到 线段pp1-pp2 的距离
else if (index2 === undefined && pointInLine(p2, pp1, pp2)) { index2 = i; }
if (index1 !== undefined && index2 !== undefined) { break; }
}
// console.log(index1 + ' : ' + index2);
if (index1 === undefined || index2 === undefined) {
debugger
return;
}
let splitResult, indiceIndex1 = index1, indiceIndex2 = index2;
cc.log("splitResults.length:"+splitResults.length);
if (splitResults.length > 0) {
for (let i = 0; i < splitResults.length; i++) {
let indices = splitResults[i];
indiceIndex1 = indices.indexOf(index1);
indiceIndex2 = indices.indexOf(index2);
if (indiceIndex1 !== -1 && indiceIndex2 !== -1) {
splitResult = splitResults.splice(i, 1)[0];
break;
}
}
}
if (!splitResult) {
splitResult = points.map((p, i) => {
return i;
});
}
for (let i = indiceIndex1 + 1; i !== (indiceIndex2+1); i++) {
if (i >= splitResult.length) {
i = 0;
}
let p = splitResult[i];
p = typeof p === 'number' ? points[p] : p;
if (p.sub(p1).magSqr() < POINT_SQR_EPSILON || p.sub(p2).magSqr() < POINT_SQR_EPSILON) {
continue;
}
newSplitResult2.push(splitResult[i]);
}
for (let i = indiceIndex2 + 1; i !== indiceIndex1+1; i++) {
if (i >= splitResult.length) {
i = 0;
}
let p = splitResult[i];
p = typeof p === 'number' ? points[p] : p;
if (p.sub(p1).magSqr() < POINT_SQR_EPSILON || p.sub(p2).magSqr() < POINT_SQR_EPSILON) {
continue;
}
newSplitResult1.push(splitResult[i]);
}
splitResults.push(newSplitResult1);
splitResults.push(newSplitResult2);
},
recalcResults: function () {
//cc.log("recalcResults");
if (!this.touching) return;
let startPoint = this.touchStartPoint;
let point = this.touchPoint;
this.ctx.clear();
this.ctx.moveTo(this.touchStartPoint.x, this.touchStartPoint.y);
this.ctx.lineTo(point.x, point.y);
this.ctx.stroke();
let manager = cc.director.getPhysicsManager();
// manager.rayCast() method calls this function only when it sees that a given line gets into the body - it doesnt see when the line gets out of it.
// I must have 2 intersection points with a body so that it can be sliced, thats why I use manager.rayCast() again, but this time from B to A - that way the point, at which BA enters the body is the point at which AB leaves it!
//检测哪些碰撞体在给定射线的路径上，射线检测将忽略包含起始点的碰撞体
let r1 = manager.rayCast(this.touchStartPoint, point, cc.RayCastType.All);
let r2 = manager.rayCast(point, this.touchStartPoint, cc.RayCastType.All);
//concat拼接两个矩阵，将结果保存到 out 矩阵。
//这个函数不创建任何内存，你需要先创建 AffineTransform 对象用来存储结果，并作为第一个参数传入函数。 out = t1 * t2
let results = r1.concat(r2);
//circle 绘制圆形路径
for (let i = 0; i < results.length; i++) {
let p = results[i].point;
this.ctx.circle(p.x, p.y, 5);
}
this.ctx.fill();
this.r1 = r1;
this.r2 = r2;
this.results = results;
},
// called every frame, uncomment this function to activate update callback
update: function (dt) {
// body maybe moving, need calc raycast results in update
this.recalcResults();
},
});
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