新增box复合体 修复vector2运算问题

source/src/Physics/Verlet/Composites/Box.ts

@@ -0,0 +1,19 @@
+///<reference path="./Composite.ts"/>
+class Box extends Composite{
+    constructor(center: Vector2, width: number, height: number, borderStiffness = 0.2, diagonalStiffness = 0.5){
+        super();
+
+        let tl = this.addParticle(new Particle(Vector2.add(center, new Vector2(-width / 2, -height / 2))));
+        let tr = this.addParticle(new Particle(Vector2.add(center, new Vector2(width / 2, -height / 2))));
+        let br = this.addParticle(new Particle(Vector2.add(center, new Vector2(width / 2, height / 2))));
+        let bl = this.addParticle(new Particle(Vector2.add(center, new Vector2(-width / 2, height / 2))));
+
+        this.addConstraint(new DistanceConstraint(tl, tr, borderStiffness));
+        this.addConstraint(new DistanceConstraint(tr, br, borderStiffness));
+        this.addConstraint(new DistanceConstraint(br, bl, borderStiffness));
+        this.addConstraint(new DistanceConstraint(bl, tl, borderStiffness));
+
+        this.addConstraint(new DistanceConstraint(tl, br, diagonalStiffness)).setCollidesWithColliders(false);
+        this.addConstraint(new DistanceConstraint(bl, tr, diagonalStiffness)).setCollidesWithColliders(false);
+    }
+}

source/src/Physics/Verlet/Composites/Composite.ts

@@ -0,0 +1,67 @@
+class Composite {
+    private _constraints: Constraint[] = [];
+
+    public friction = new Vector2(0.98, 1);
+    public drawParticles: boolean = true;
+    public drawConstraints: boolean = true;
+    public particles: Particle[] = [];
+    /**
+     * 处理解决所有约束条件
+     */
+    public solveConstraints(){
+        for (let i = this._constraints.length - 1; i >= 0; i --){
+            this._constraints[i].solve();
+        }
+    }
+
+    public addParticle(particle: Particle){
+        this.particles.push(particle);
+        return particle;
+    }
+
+    public addConstraint<T extends Constraint>(constraint: T): T{
+        this._constraints.push(constraint);
+        constraint.composite = this;
+        return constraint;
+    }
+
+    public removeConstraint(constraint: Constraint){
+        this._constraints.remove(constraint);
+    }
+
+    public updateParticles(deltaTimeSquared: number, gravity: Vector2){
+        for (let j = 0; j < this.particles.length; j ++){
+            let p = this.particles[j];
+            if (p.isPinned){
+                p.position = p.pinnedPosition;
+                continue;
+            }
+
+            p.applyForce(Vector2.multiply(new Vector2(p.mass, p.mass), gravity));
+
+            let vel = Vector2.multiply(Vector2.subtract(p.position, p.lastPosition), this.friction);
+            let nextPos = Vector2.add(Vector2.add(p.position, vel), Vector2.multiply(p.acceleration, new Vector2(0.5 * deltaTimeSquared, 0.5 * deltaTimeSquared)));
+
+            p.lastPosition = p.position;
+            p.position = nextPos;
+            p.acceleration.x = p.acceleration.y = 0;
+        }
+    }
+
+    public debugRender(graphics: egret.Graphics){
+        if (this.drawConstraints){
+            for (let i = 0; i < this._constraints.length; i ++){
+                this._constraints[i].debugRender(graphics);
+            }
+        }
+
+        if (this.drawParticles){
+            for (let i = 0; i < this.particles.length; i ++){
+                let size = this.particles[i].radius ? this.particles[i].radius : 4;
+                graphics.lineStyle(4, DebugDefaults.verletParticle);
+                graphics.drawRect(this.particles[i].position.x, this.particles[i].position.y, size, size);
+                graphics.endFill();
+            }
+        }
+    }
+}