flash 切割游戏

更新时间：2022-09-02 14:56:07

引用：http://bbs.9ria.com/thread-114856-1-1.html

现在就要使用相同的思想以最真实的方式来切割刚体。

这是我做的效果：

在舞台上点击鼠标，会有一个小球以随机的速度从边上射出，看看它是怎么切割这块木桩的。我使用了“bullet time”来做这个东西，所以你可以看看它是怎么工作的，并且由于当这个小球以高速度飞行的时候，我有的时候会遇到一些问题，但是现在这里只是一个原型。

不管怎样，它是按下面的方式运行的：

当小球触碰到木桩的时候，我自定义的接触监听器对它进行了监听；

这时，我知道小球的位置和速度。假设小球可以切断这块木桩，通过小球的位置以及方向，我可以确定一条切割线；

将切割线应用到木桩上面，将它切成两半；

最后我将这个小球克隆，创建另外一个新的小球，这个小球与原来的小球有相同的速度和方向，这个小球将会和木桩相碰，用来展现小球和木桩碎片相碰撞的效果。

基本上就是这样了。

我将所有带有注释的源码贴出来：

package {
import flash.display.Sprite;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.geom.Matrix;
import flash.display.BitmapData;
import Box2D.Dynamics.*;
import Box2D.Collision.*;
import Box2D.Collision.Shapes.*;
import Box2D.Common.Math.*;
public class Main extends Sprite {
private var world:b2World=new b2World(new b2Vec2(0,10),true);
// You can see the reason for creating the enterPointsVec in the coments in the intersection() method.
private var enterPointsVec:Vector.<b2Vec2> = new Vector.<b2Vec2>();
private var numEnterPoints:int=0;
private var worldScale:Number=30;
// custom contact listener
private var customContact=new CustomContactListener();
public function Main() {
// defining the custom contact listener
world.SetContactListener(customContact);
// calling the debug draw. This is used to show you the bitmaps are correctly applied,
// and because I did not want to draw the walls :)
debugDraw();
// this is the BitmapData representation of the wood
// check the library to see both the raw image and the sprite
var woodBitmap:BitmapData=new BitmapData(50,400);
woodBitmap.draw(new WoodImage());
// adding the four static, undestroyable walls;
addWall(320,480,640,20);
addWall(320,0,640,20);
addWall(0,240,20,480);
addWall(640,240,20,480);
// createBody builds the final body and applies the bitmap.
createBody(400,270,new <b2Vec2>[new b2Vec2(-25,-200),new b2Vec2(25,-200),new b2Vec2(25,200),new b2Vec2(-25,200)],woodBitmap);
// You can see the reason for creating the enterPointsVec in the coments in the intersection() method.
enterPointsVec=new Vector.<b2Vec2>(numEnterPoints);
// listeners
stage.addEventListener(MouseEvent.MOUSE_DOWN, shoot);
addEventListener(Event.ENTER_FRAME, update);
}
// my old friend debugDraw function
private function debugDraw():void {
var debugDraw:b2DebugDraw = new b2DebugDraw();
var debugSprite:Sprite = new Sprite();
addChild(debugSprite);
debugDraw.SetSprite(debugSprite);
debugDraw.SetDrawScale(worldScale);
debugDraw.SetFlags(b2DebugDraw.e_shapeBit|b2DebugDraw.e_jointBit);
debugDraw.SetFillAlpha(0.5);
world.SetDebugDraw(debugDraw);
}
// function that will add the sphere and launch it
// arguments are respectively x position, y position, radius, x velocity and y velocity
private function addSphere(pX:Number,pY:Number,r:Number,vX:Number,vY:Number):void {
var theSphere:b2Body;
var sphereShape:b2CircleShape=new b2CircleShape(r/worldScale);
var sphereFixture:b2FixtureDef = new b2FixtureDef();
sphereFixture.density=1;
sphereFixture.friction=3;
sphereFixture.restitution=0.1;
sphereFixture.shape=sphereShape;
var sphereBodyDef:b2BodyDef = new b2BodyDef();
sphereBodyDef.type=b2Body.b2_dynamicBody;
sphereBodyDef.position.Set(pX/worldScale,pY/worldScale);
sphereBodyDef.bullet=true;
sphereBodyDef.userData={assetName:"sphere",collided:false};
theSphere=world.CreateBody(sphereBodyDef);
theSphere.CreateFixture(sphereFixture);
theSphere.SetLinearVelocity(new b2Vec2(vX,vY));
}
// simple function to add a static wall
private function addWall(pX:Number,pY:Number,w:Number,h:Number):void {
var wallShape:b2PolygonShape = new b2PolygonShape();
wallShape.SetAsBox(w/worldScale/2,h/worldScale/2);
var wallFixture:b2FixtureDef = new b2FixtureDef();
wallFixture.density=0;
wallFixture.friction=1;
wallFixture.restitution=0.5;
wallFixture.shape=wallShape;
var wallBodyDef:b2BodyDef = new b2BodyDef();
wallBodyDef.position.Set(pX/worldScale,pY/worldScale);
wallBodyDef.userData={assetName:"wall"};
var wall:b2Body=world.CreateBody(wallBodyDef);
wall.CreateFixture(wallFixture);
numEnterPoints++;
}
// function to create and texture a dynamic body
private function createBody(xPos:Number, yPos:Number, verticesArr:Vector.<b2Vec2>, texture:BitmapData) {
// I need this temp vector to convert pixels coordinates to Box2D meters coordinates
var vec:Vector.<b2Vec2>=new Vector.<b2Vec2>();
for (var i:Number=0; i<verticesArr.length; i++) {
vec.push(new b2Vec2(verticesArr[i].x/worldScale,verticesArr[i].y/worldScale));
}
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.type=b2Body.b2_dynamicBody;
var boxDef:b2PolygonShape = new b2PolygonShape();
boxDef.SetAsVector(vec);
bodyDef.position.Set(xPos/worldScale, yPos/worldScale);
// custom userData used to map the texture;
bodyDef.userData={assetName:"wood",textureData:new userData(numEnterPoints,vec,texture)};
addChild(bodyDef.userData.textureData);
var fixtureDef:b2FixtureDef = new b2FixtureDef();
fixtureDef.density=1;
fixtureDef.friction=0.2;
fixtureDef.restitution=0.5;
fixtureDef.shape=boxDef;
var tempBox:b2Body=world.CreateBody(bodyDef);
tempBox.CreateFixture(fixtureDef);
numEnterPoints++;
}
// function to shoot the ball
private function shoot(e:MouseEvent) {
addSphere(20,240,15,50,Math.random()*40-20);
stage.removeEventListener(MouseEvent.MOUSE_DOWN,shoot);
}
// update function to simulate and render the world
public function update(e:Event):void {
world.Step(1/300, 10, 10);
world.ClearForces();
var spr:Sprite;
for (var b:b2Body = world.GetBodyList(); b; b = b.GetNext()) {
if (b.GetUserData()!=null) {
// according to the collision listener, I am here when the sphere hits the wood
if (b.GetUserData().assetName=="sphere"&&b.GetUserData().collided) {
// retrieving sphere velocity
var sphereVelocity:b2Vec2=b.GetLinearVelocity();
// getting direction according to velocity
var sphereDirection:Number=Math.atan2(sphereVelocity.y,sphereVelocity.x);
// getting sphere position
var colX:Number=b.GetPosition().x;
var colY:Number=b.GetPosition().y;
// clone the sphere
addSphere(colX*worldScale,colY*worldScale,15,sphereVelocity.x,sphereVelocity.y);
// perform the raycast
world.RayCast(intersection, new b2Vec2(colX,colY), new b2Vec2(colX+5*Math.cos(sphereDirection),colY+5*Math.sin(sphereDirection)));
world.RayCast(intersection, new b2Vec2(colX+5*Math.cos(sphereDirection),colY+5*Math.sin(sphereDirection)), new b2Vec2(colX,colY));
// destroy the original sphere
world.DestroyBody(b);
}
}
}
// update graphics on stage
for (b = world.GetBodyList(); b; b = b.GetNext()) {
if (b.GetUserData()!=null) {
spr=b.GetUserData().textureData;
if (spr) {
spr.x=b.GetPosition().x*worldScale;
spr.y=b.GetPosition().y*worldScale;
spr.rotation=b.GetAngle()*180/Math.PI;
}
}
}
world.DrawDebugData();
}
private function intersection(fixture:b2Fixture, point:b2Vec2, normal:b2Vec2, fraction:Number):Number {
if (fixture.GetBody().GetUserData()) {
if (fixture.GetBody().GetUserData().textureData!=null) {
var spr:Sprite=fixture.GetBody().GetUserData().textureData;
// Throughout this whole code I use only one global vector, and that is enterPointsVec. Why do I need it you ask?
// Well, the problem is that the world.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 world.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!
// For that reason, I use a vector enterPointsVec, where I store the points, at which AB enters the body. And later on, if I see that BA enters a body, which has been entered already by AB, I fire the splitObj() function!
// I need a unique ID for each body, in order to know where its corresponding enter point is - I store that id in the userData of each body.
if (spr is userData) {
var userD:userData=spr as userData;
if (enterPointsVec[userD.id]) {
// If this body has already had an intersection point, then it now has two intersection points, thus it must be split in two - thats where the splitObj() method comes in.
splitObj(fixture.GetBody(), enterPointsVec[userD.id], point.Copy());
}
else {
enterPointsVec[userD.id]=point;
}
}
}
}
return 1;
}
// function to get the area of a shape. I will remove tiny shape to increase performance
private function getArea(vs:Vector.<b2Vec2>, count:uint):Number {
var area:Number=0.0;
var p1X:Number=0.0;
var p1Y:Number=0.0;
var inv3:Number=1.0/3.0;
for (var i:int = 0; i < count; ++i) {
var p2:b2Vec2=vs[i];
var p3:b2Vec2=i+1<count?vs[int(i+1)]:vs[0];
var e1X:Number=p2.x-p1X;
var e1Y:Number=p2.y-p1Y;
var e2X:Number=p3.x-p1X;
var e2Y:Number=p3.y-p1Y;
var D:Number = (e1X * e2Y - e1Y * e2X);
var triangleArea:Number=0.5*D;
area+=triangleArea;
}
return area;
}
private function splitObj(sliceBody:b2Body, A:b2Vec2, B:b2Vec2):void {
var origFixture:b2Fixture=sliceBody.GetFixtureList();
var poly:b2PolygonShape=origFixture.GetShape() as b2PolygonShape;
var verticesVec:Vector.<b2Vec2>=poly.GetVertices(),numVertices:int=poly.GetVertexCount();
var shape1Vertices:Vector.<b2Vec2> = new Vector.<b2Vec2>(), shape2Vertices:Vector.<b2Vec2> = new Vector.<b2Vec2>();
var origUserData:userData=sliceBody.GetUserData().textureData,origUserDataId:int=origUserData.id,d:Number;
var polyShape:b2PolygonShape=new b2PolygonShape();
var body:b2Body;
// First, I destroy the original body and remove its Sprite representation from the childlist.
world.DestroyBody(sliceBody);
removeChild(origUserData);
// The world.RayCast() method returns points in world coordinates, so I use the b2Body.GetLocalPoint() to convert them to local coordinates.;
A=sliceBody.GetLocalPoint(A);
B=sliceBody.GetLocalPoint(B);
// I use shape1Vertices and shape2Vertices to store the vertices of the two new shapes that are about to be created.
// Since both point A and B are vertices of the two new shapes, I add them to both vectors.
shape1Vertices.push(A, B);
shape2Vertices.push(A, B);
// I iterate over all vertices of the original body. ;
// I use the function det() ("det" stands for "determinant") to see on which side of AB each point is standing on. The parameters it needs are the coordinates of 3 points:
// - if it returns a value >0, then the three points are in clockwise order (the point is under AB)
// - if it returns a value =0, then the three points lie on the same line (the point is on AB)
// - if it returns a value <0, then the three points are in counter-clockwise order (the point is above AB).
for (var i:Number=0; i<numVertices; i++) {
d=det(A.x,A.y,B.x,B.y,verticesVec[i].x,verticesVec[i].y);
if (d>0) {
shape1Vertices.push(verticesVec[i]);
}
else {
shape2Vertices.push(verticesVec[i]);
}
}
// In order to be able to create the two new shapes, I need to have the vertices arranged in clockwise order.
// I call my custom method, arrangeClockwise(), which takes as a parameter a vector, representing the coordinates of the shape's vertices and returns a new vector, with the same points arranged clockwise.
shape1Vertices=arrangeClockwise(shape1Vertices);
shape2Vertices=arrangeClockwise(shape2Vertices);
// setting the properties of the two newly created shapes
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.type=b2Body.b2_dynamicBody;
bodyDef.position=sliceBody.GetPosition();
var fixtureDef:b2FixtureDef = new b2FixtureDef();
fixtureDef.density=origFixture.GetDensity();
fixtureDef.friction=origFixture.GetFriction();
fixtureDef.restitution=origFixture.GetRestitution();
// creating the first shape, if big enough
if (getArea(shape1Vertices,shape1Vertices.length)>=0.05) {
polyShape.SetAsVector(shape1Vertices);
fixtureDef.shape=polyShape;
bodyDef.userData={assetName:"debris",textureData:new userData(origUserDataId,shape1Vertices,origUserData.texture)};
addChild(bodyDef.userData.textureData);
enterPointsVec[origUserDataId]=null;
body=world.CreateBody(bodyDef);
body.SetAngle(sliceBody.GetAngle());
body.CreateFixture(fixtureDef);
}
// creating the second shape, if big enough;
if (getArea(shape2Vertices,shape2Vertices.length)>=0.05) {
polyShape.SetAsVector(shape2Vertices);
fixtureDef.shape=polyShape;
bodyDef.userData={assetName:"debris",textureData:new userData(origUserDataId,shape2Vertices,origUserData.texture)};
addChild(bodyDef.userData.textureData);
enterPointsVec.push(null);
numEnterPoints++;
body=world.CreateBody(bodyDef);
body.SetAngle(sliceBody.GetAngle());
body.CreateFixture(fixtureDef);
}
}
private function arrangeClockwise(vec:Vector.<b2Vec2>):Vector.<b2Vec2> {
// The algorithm is simple:
// First, it arranges all given points in ascending order, according to their x-coordinate.
// Secondly, it takes the leftmost and rightmost points (lets call them C and D), and creates tempVec, where the points arranged in clockwise order will be stored.
// Then, it iterates over the vertices vector, and uses the det() method I talked about earlier. It starts putting the points above CD from the beginning of the vector, and the points below CD from the end of the vector.
// That was it!
var n:int=vec.length,d:Number,i1:int=1,i2:int=n-1;
var tempVec:Vector.<b2Vec2>=new Vector.<b2Vec2>(n),C:b2Vec2,D:b2Vec2;
vec.sort(comp1);
tempVec[0]=vec[0];
C=vec[0];
D=vec[n-1];
for (var i:Number=1; i<n-1; i++) {
d=det(C.x,C.y,D.x,D.y,vec[i].x,vec[i].y);
if (d<0) {
tempVec[i1++]=vec[i];
}
else {
tempVec[i2--]=vec[i];
}
}
tempVec[i1]=vec[n-1];
return tempVec;
}
private function comp1(a:b2Vec2, b:b2Vec2):Number {
// This is a compare function, used in the arrangeClockwise() method - a fast way to arrange the points in ascending order, according to their x-coordinate.
if (a.x>b.x) {
return 1;
}
else if (a.x<b.x) {
return -1;
}
return 0;
}
private function det(x1:Number, y1:Number, x2:Number, y2:Number, x3:Number, y3:Number):Number {
// This is a function which finds the determinant of a 3x3 matrix.
// If you studied matrices, you'd know that it returns a positive number if three given points are in clockwise order, negative if they are in anti-clockwise order and zero if they lie on the same line.
// Another useful thing about determinants is that their absolute value is two times the face of the triangle, formed by the three given points.
return x1*y2+x2*y3+x3*y1-y1*x2-y2*x3-y3*x1;
}
}
}

复制代码

下面的是自定义的接触监听器：

package {
import Box2D.Dynamics.*;
import Box2D.Collision.*;
import Box2D.Dynamics.Contacts.*;
import Box2D.Common.Math.*;
class CustomContactListener extends b2ContactListener {
override public function PreSolve(contact:b2Contact, oldManifold:b2Manifold):void {
var nameA:String=contact.GetFixtureA().GetBody().GetUserData().assetName.toString();
var nameB:String=contact.GetFixtureB().GetBody().GetUserData().assetName.toString();
if ((nameA=="wood" && nameB=="sphere")||(nameA=="sphere" && nameB=="wood")) {
if (nameA=="sphere") {
contact.GetFixtureA().GetBody().GetUserData().collided=true
}
else {
contact.GetFixtureB().GetBody().GetUserData().collided=true
}
}
}
}
}

复制代码

我希望这会给你设计自己的游戏带来一些灵感。源码下载。

flash 切割游戏

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