详解Flash AS代码实现弹弓弓弦弹性形变
我们用Flash ActionScript代码制作一个模拟弹弓弓弦弹性形变的小游戏教程,我们一步一步由浅入深来详细说明制作步骤。
思路:准备三个小球元件,使其中一个小球可以拖动,在使它沿着一条线移动,用ActionScript代码计算移动的角度,最后实现弹弓弓弦弹性形变的一个互动游戏。
一、Flash制作小球随鼠标拖动
启动Flash,首先我们绘制两个元件,非常简单的。绘制一个小球然后转变为影片剪辑元件,同样方法再建议一个不同颜色的小球的影片剪辑。
然后在主场景中直接输入如下代码:
attachMovie("sling", "sling_1", _root.getNextHighestDepth(), {_x:20, _y:200}); attachMovie("sling", "sling_2", _root.getNextHighestDepth(), {_x:480, _y:200}); attachMovie("ball", "ball", _root.getNextHighestDepth(), {_x:250, _y:100}); _root.createEmptyMovieClip("elastic", _root.getNextHighestDepth()); ball.onPress = function() { startDrag(this); }; ball.onRelease = function() { stopDrag(); }; |
二、Flash制作随小球移动的弦
然后我们通过修改上面的代码,在两个小球之间绘制一条线,可以随中间小球任意移动。
attachMovie("sling", "sling_1", _root.getNextHighestDepth(), {_x:20, _y:200}); attachMovie("sling", "sling_2", _root.getNextHighestDepth(), {_x:480, _y:200}); attachMovie("ball", "ball", _root.getNextHighestDepth(), {_x:250, _y:100}); _root.createEmptyMovieClip("elastic", _root.getNextHighestDepth()); ball.onPress = function() { startDrag(this); }; ball.onRelease = function() { stopDrag(); }; elastic.onEnterFrame = function() { this.clear(); this.lineStyle(2, 0x009900); this.moveTo(sling_1._x, sling_1._y); if (ball._y>182) { dist_x = ball._x-sling_1._x; dist_y = ball._y-sling_1._y; distance_from_sling = Math.sqrt(dist_x*dist_x+dist_y*dist_y); elastic_length = Math.sqrt(distance_from_sling*distance_from_sling-18*18); angle = Math.atan2(dist_y, dist_x)+Math.asin(18/distance_from_sling); this.lineTo(sling_1._x+elastic_length*Math.cos(angle), sling_1._y+elastic_length*Math.sin(angle)); } else { this.lineTo(sling_2._x, sling_2._y); } this.moveTo(sling_2._x, sling_2._y); if (ball._y>182) { dist_x = ball._x-sling_2._x; dist_y = ball._y-sling_2._y; distance_from_sling = Math.sqrt(dist_x*dist_x+dist_y*dist_y); elastic_length = Math.sqrt(distance_from_sling*distance_from_sling-18*18); angle = Math.atan2(dist_y, dist_x)+Math.asin(18/distance_from_sling)*-1; this.lineTo(sling_2._x+elastic_length*Math.cos(angle), sling_2._y+elastic_length*Math.sin(angle)); } else { this.lineTo(sling_2._x, sling_2._y); } }; |
三、Flash计算弦的形变角度
在这里我们可以很轻松的计算出小球在线上的角度来。
稍微做一下改动。
attachMovie("sling", "sling_1", _root.getNextHighestDepth(), {_x:20, _y:200}); attachMovie("sling", "sling_2", _root.getNextHighestDepth(), {_x:480, _y:200}); attachMovie("ball", "ball", _root.getNextHighestDepth(), {_x:250, _y:100}); _root.createEmptyMovieClip("elastic", _root.getNextHighestDepth()); xspeed = 0; yspeed = 0; fire = false; ball.onPress = function() { fire = false; startDrag(this); }; ball.onRelease = function() { stopDrag(); fire = true; }; ball.onEnterFrame = function() { if (fire) { this._x += (xspeed*0.001); this._y += (yspeed*0.001); } }; elastic.onEnterFrame = function() { this.clear(); this.lineStyle(2, 0x009900); this.moveTo(sling_1._x, sling_1._y); if (ball._y>182) { dist_x = ball._x-sling_1._x; dist_y = ball._y-sling_1._y; distance_from_sling = Math.sqrt(dist_x*dist_x+dist_y*dist_y); elastic_length = Math.sqrt(distance_from_sling*distance_from_sling-18*18); angle = Math.atan2(dist_y, dist_x)+Math.asin(18/distance_from_sling); saved_angle = angle; this.lineTo(sling_1._x+elastic_length*Math.cos(angle), sling_1._y+elastic_length*Math.sin(angle)); this.lineTo(ball._x,ball._y); } else { this.lineTo(sling_2._x, sling_2._y); } this.moveTo(sling_2._x, sling_2._y); if (ball._y>182) { dist_x = ball._x-sling_2._x; dist_y = ball._y-sling_2._y; distance_from_sling = Math.sqrt(dist_x*dist_x+dist_y*dist_y); elastic_length = Math.sqrt(distance_from_sling*distance_from_sling-18*18); angle = Math.atan2(dist_y, dist_x)+Math.asin(18/distance_from_sling)*-1; this.lineTo(sling_2._x+elastic_length*Math.cos(angle), sling_2._y+elastic_length*Math.sin(angle)); this.lineTo(ball._x,ball._y); } else { this.lineTo(sling_2._x, sling_2._y); } }; |
四、Flash制作小球与弦的互动运动 最后我们让小球自动运动或者你可以用鼠标拖动小球。
var ball:MovieClip = _root.attachMovie("ball", "ball", 2, {_x:250, _y:100}); var elastic:MovieClip = _root.createEmptyMovieClip("elastic", 1); var point1:MovieClip = _root.attachMovie("sling", "point1", 3, {_x:50, _y:200}); var point2:MovieClip = _root.attachMovie("sling", "point2", 4, {_x:450, _y:200}); var gravity = 0.1; var angle1:Number = 0; var angle2:Number = 0; var radius:Number = 13.0; // Or whatever half the width of your ball is. var elasticCoefficient:Number = 0.001; // This number will affect the stretchiness of the sling. The greater the number // the tighter the elastic will be. var released:Boolean = true; var forced:Boolean = false; var acc:Object = {x:0, y:0}; var vel:Object = {x:0, y:0}; _root.onMouseDown = function() { ball._x = _root._xmouse; ball._y = _root._ymouse; ball.startDrag(); _root.released = false; vel.x = 0; vel.y = 0; }; _root.onMouseUp = function() { ball.stopDrag(); _root.released = true; }; ball.onPress = function() { ball.startDrag(); _root.released = false; vel.x = 0; vel.y = 0; }; ball.onRelease = function() { ball.stopDrag(); _root.released = true; }; _root.onEnterFrame = function() { elastic.clear(); elastic.lineStyle(3, 0xFF0000); if (released) { ball._x += vel.x; ball._y += vel.y; } if (ball._y>=187) { /* This area differs from the code in the tutorial. The reason for that is I didn't read the code, I just looked at the examples. I try to gain experience with problem-solving by doing things as close to by myself as possible. */ forced = true; var x1:Number = ball._x-point1._x; var y1:Number = ball._y-point1._y; var x2:Number = point2._x-ball._x; var y2:Number = point2._y-ball._y; var distance1:Number = Math.sqrt(x1*x1+y1*y1); var distance2:Number = Math.sqrt(x2*x2+y2*y2); _root.angle1 = Math.atan2(y1, x1); _root.angle2 = Math.atan2(y2, x2); var xOffset:Number = Math.cos(angle1+Math.PI/2)*radius; var yOffset:Number = Math.sin(angle1+Math.PI/2)*radius; var xOffset2:Number = Math.cos(angle2+Math.PI/2)*radius; var yOffset2:Number = Math.sin(angle2+Math.PI/2)*radius; angle1 += Math.sin(radius/distance1); angle2 += Math.sin(radius/distance2)*-1; elastic.moveTo(point1._x, point1._y); elastic.lineTo(ball._x+xOffset, ball._y+yOffset); elastic.moveTo(point2._x, point2._y); elastic.lineTo(ball._x+xOffset2, ball._y+yOffset2); } else { forced = false; elastic.moveTo(point1._x, point1._y); elastic.lineTo(point2._x, point2._y); } acc.x = 0; acc.y = 0; acc.y = gravity; if (released && forced) { /* This section applies the force of the sling to the ball in terms of acceleration based on the stretching of the sling, in the direction of the displacement, scaled by a coefficient that also encapsulates the mass of the ball. */ acc.x += distance1*Math.sin(angle2)*elasticCoefficient; acc.y += -distance1*Math.cos(angle1)*elasticCoefficient; acc.x += distance2*Math.sin(angle1)*elasticCoefficient; acc.y += -distance2*Math.cos(angle2)*elasticCoefficient; } if (released) { vel.x += acc.x; vel.y += acc.y; } }; |
|