Question

这就是我想要实现的目标 - GRASS Animation（期望动画）

这是项目目前所处的位置--My hair animation

这是上面代码的结构化代码 - 我的头发动画（通过markE）--markE`s code of hair animation

问题： -

我可以给毛发动作，但动画应该更像是自由流动的波状草。它现在不是很光滑。可以做什么使头发以更自然的方式流动。如果可能的话，请给我一个小样本!!!

    <canvas id="myCanvas" width="500" height="500" style="background-color: antiquewhite" ></canvas>

JAVASCRIPT

//mouse position
var x2=0;
var y2=0;

window.addEventListener("mousemove",function(){moving(event);init()},false)

//these variables define the bend in our bezier curve
var bend9=0;
var bend8=0;
var bend7=0;
var bend6=0;
var bend5=0;
var bend4=0;
var bend3=0;
var bend2=0;
var bend1=0;

//function to get the mouse cordinates
function moving(event) {
    bend_value();//this function is defined below
    try
    {
        x2 = event.touches[0].pageX;
        y2 = event.touches[0].pageY;
    }
    catch (error)
    {
        try
        {
            x2 = event.clientX;
            y2 = event.clientY;
        }
        catch (e)
        {
        }
    }

    try
    {
        event.preventDefault();
    }
    catch (e)
    {
    }
    if(between(y2,204,237) && between(x2,115,272))
    {
    console.log("Xmove="+x2,"Ymove="+y2)
    }

}

//function for declaring range of bezier curve
function between(val, min, max)
{
    return val >= min && val <= max;
}

(function() {
    hair = function() {
        return this;
    };

    hair.prototype={

     draw_hair:function(a,b,c,d,e,f,g,h){

            var sx  =136+a;//start position of curve.used in moveTo(sx,sy)
            var sy  =235+b;
            var cp1x=136+c;//control point 1
            var cp1y=222+d;
            var cp2x=136+e;//control point 2
            var cp2y=222+f;
            var endx=136+g;//end points
            var endy=210+h;

         var canvas = document.getElementById('myCanvas');
         var context = canvas.getContext('2d');
//         context.clearRect(0, 0,500,500);
         context.strokeStyle="grey";
         context.lineWidth="8";
         context.beginPath();
         context.moveTo(sx,sy);
         context.bezierCurveTo(cp1x,cp1y,cp2x,cp2y,endx,endy);
         context.lineCap = 'round';
         context.stroke();
//         context.restore();
//         context.save();
    }
};
})();

//this function provides and calculate the bend on mousemove
function bend_value(){
    var ref1=135;//this is ref point for  hair or curve no 1
    var ref2=150;//hair no 2 and so on
    var ref3=165;
    var ref4=180;
    var ref5=195;
    var ref6=210;
    var ref7=225;
    var ref8=240;
    var ref9=255;
if(between(x2,115,270) && between(y2,205,236))
{
    if(x2>=135 && x2<=145){bend1=(x2-ref1)*(2.2);}
    if(x2<=135 && x2>=125){bend1=(x2-ref1)*(2.2);}

    if(x2>=150 && x2<=160){bend2=(x2-ref2)*(2.2);}
    if(x2<=150 && x2>=140){bend2=(x2-ref2)*(2.2);}

    if(x2>=165 && x2<=175){bend3=(x2-ref3)*(2.2);}
    if(x2<=165 && x2>=155){bend3=(x2-ref3)*(2.2);}

    if(x2>=180 && x2<=190){bend4=(x2-ref4)*(2.2);}
    if(x2<=180 && x2>=170){bend4=(x2-ref4)*(2.2);}

    if(x2>=195 && x2<=205){bend5=(x2-ref5)*(2.2);}
    if(x2<=195 && x2>=185){bend5=(x2-ref5)*(2.2);}

    if(x2>=210 && x2<=220){bend6=(x2-ref6)*(2.2);}
    if(x2<=210 && x2>=200){bend6=(x2-ref6)*(2.2);}

    if(x2>=225 && x2<=235){bend7=(x2-ref7)*(2.2);}
    if(x2<=225 && x2>=215){bend7=(x2-ref7)*(2.2);}

    if(x2>=240 && x2<=250){bend8=(x2-ref8)*(2.2);}
    if(x2<=240 && x2>=230){bend8=(x2-ref8)*(2.2);}

    if(x2>=255 && x2<=265){bend9=(x2-ref9)*(2.2);}
    if(x2<=255 && x2>=245){bend9=(x2-ref9)*(2.2);}
    }
}

function init(){//this function draws each hair/curve
    var canvas = document.getElementById('myCanvas');
    var context = canvas.getContext('2d');
    var clear=context.clearRect(0, 0,500,500);
    var save=context.save();

//   /* console.log("bend2="+bend2)
//    console.log("bend3="+bend3)
//    console.log("bend4="+bend4)
//    console.log("bend5="+bend5)
//    console.log("bend6="+bend6)
//    console.log("bend7="+bend7)
//    console.log("bend8="+bend8)
//    console.log("bend9="+bend9)*/

    hd1 = new hair();//hd1 stands for hair draw 1.this is an instance created for drawing hair no 1
    clear;
    hd1.draw_hair(0,0,0,0,0,0,0+bend1/2,0);//these parameters passed to function drawhair and bend is beint retrieved from function bend_value()
    save;

    hd2 = new hair();
    clear;
    hd2.draw_hair(15,0,15,0,15,0,15+bend2/2,0);
    save;

    hd3 = new hair();
    clear;
    hd3.draw_hair(30,0,30,0,30,0,30+bend3/2,0);
    save;

    hd4 = new hair();
    clear;
    hd4.draw_hair(45,0,45,0,45,0,45+bend4/2,0);
    save;

    hd5 = new hair();
    clear;
    hd5.draw_hair(60,0,60,0,60,0,60+bend5/2,0);
    save;
 }

window.onload = function() {
    init();
    disableSelection(document.body)
}

function disableSelection(target){
    if (typeof target.onselectstart!="undefined") //IE
        target.onselectstart=function(){return false}
    else if (typeof target.style.MozUserSelect!="undefined") //Firefox
        target.style.MozUserSelect="none"
    else //All other ie: Opera
        target.onmousedown=function(){return false}
    target.style.cursor = "default"
}

Answer 1

更新：我正在调整code以生成请求的结果并对其进行评论。

(function() { // The code is encapsulated in a self invoking function  to isolate the scope
  "use strict";

   // The following lines creates shortcuts to the constructors of the Box2D types used
   var B2Vec2 = Box2D.Common.Math.b2Vec2,
      B2BodyDef = Box2D.Dynamics.b2BodyDef,
      B2Body = Box2D.Dynamics.b2Body,
      B2FixtureDef = Box2D.Dynamics.b2FixtureDef,
      B2Fixture = Box2D.Dynamics.b2Fixture,
      B2World = Box2D.Dynamics.b2World,
      B2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape,
      B2RevoluteJoint = Box2D.Dynamics.Joints.b2RevoluteJoint,
      B2RevoluteJointDef = Box2D.Dynamics.Joints.b2RevoluteJointDef;

  // This makes sure that there is a method to request a callback to update the graphics for next frame
  window.requestAnimationFrame =
    window.requestAnimationFrame || // According to the standard
    window.mozRequestAnimationFrame || // For mozilla
    window.webkitRequestAnimationFrame || // For webkit
    window.msRequestAnimationFrame || // For ie
    function (f) { window.setTimeout(function () { f(Date.now()); }, 1000/60); }; // If everthing else fails

  var world = new B2World(new B2Vec2(0, -10), true), // Create a world with gravity
      physicalObjects = [], // Maintain a list of the simulated objects
      windInput = 0, // The input for the wind in the current frame
      wind = 0, // The current wind (smoothing the input values + randomness)
      STRAW_COUNT = 10, // Number of straws
      GRASS_RESET_SPEED = 2, // How quick should the straw reset to its target angle
      POWER_MOUSE_WIND = 120, // How much does the mouse affect the wind
      POWER_RANDOM_WIND = 180; // How much does the randomness affect the wind

  // GrassPart is a prototype for a piece of a straw. It has the following properties
  //  position: the position of the piece
  //  density: the density of the piece
  //  target: the target angle of the piece
  //  statik: a boolean stating if the piece is static (i.e. does not move)
  function GrassPart(position, density, target, statik) {
    this.width = 0.05;
    this.height = 0.5;
    this.target = target;

    // To create a physical body in Box2D you have to setup a body definition
    // and create at least one fixture.
    var bdef = new B2BodyDef(), fdef = new B2FixtureDef();
    // In this example we specify if the body is static or not (the grass roots 
    // has to be static to keep the straw in its position), and its original
    // position.
    bdef.type = statik? B2Body.b2_staticBody : B2Body.b2_dynamicBody;
    bdef.position.SetV(position);

    // The fixture of the piece is a box with a given density. The negative group index
    // makes sure that the straws does not collide.
    fdef.shape = new B2PolygonShape();
    fdef.shape.SetAsBox(this.width/2, this.height/2);
    fdef.density = density;
    fdef.filter.groupIndex = -1;

    // The body and fixture is created and added to the world
    this.body = world.CreateBody(bdef);
    this.body.CreateFixture(fdef);
  }

  // This method is called for every frame of animation. It strives to reset the original
  // angle of the straw (the joint). The time parameter is unused here but contains the
  // current time.
  GrassPart.prototype.update = function (time) {
    if (this.joint) {
      this.joint.SetMotorSpeed(GRASS_RESET_SPEED*(this.target - this.joint.GetJointAngle()));
    }
  };

  // The link method is used to link the pieces of the straw together using a joint
  // other: the piece to link to
  // torque: the strength of the joint (stiffness)
  GrassPart.prototype.link = function(other, torque) {
    // This is all Box2D specific. Look it up in the manual.
    var jdef = new B2RevoluteJointDef();
    var p = this.body.GetWorldPoint(new B2Vec2(0, 0.5)); // Get the world coordinates of where the joint
    jdef.Initialize(this.body, other.body, p);
    jdef.maxMotorTorque = torque;
    jdef.motorSpeed = 0;
    jdef.enableMotor = true;

    // Add the joint to the world
    this.joint = world.CreateJoint(jdef);
  };

  // A prototype for a straw of grass
  // position: the position of the bottom of the root of the straw
  function Grass(position) {
    var pos = new B2Vec2(position.x, position.y);
    var angle = 1.2*Math.random() - 0.6; // Randomize the target angle

    // Create three pieces, the static root and to more, and place them in line.
    // The second parameter is the stiffness of the joints. It controls how the straw bends.
    // The third is the target angle and different angles are specified for the pieces.
    this.g1 = new GrassPart(pos, 1, angle/4, true); // This is the static root
    pos.Add(new B2Vec2(0, 1));
    this.g2 = new GrassPart(pos, 0.75, angle);
    pos.Add(new B2Vec2(0, 1));
    this.g3 = new GrassPart(pos, 0.5);

    // Link the pieces into a straw
    this.g1.link(this.g2, 20);
    this.g2.link(this.g3, 3);

    // Add the pieces to the list of simulate objects
    physicalObjects.push(this.g1);
    physicalObjects.push(this.g2);
    physicalObjects.push(this.g3);
  }

  Grass.prototype.draw = function (context) {
      var p = new B2Vec2(0, 0.5);
      var p1 = this.g1.body.GetWorldPoint(p);
      var p2 = this.g2.body.GetWorldPoint(p);
      var p3 = this.g3.body.GetWorldPoint(p);

      context.strokeStyle = 'grey';
      context.lineWidth = 0.4;
      context.lineCap = 'round';

      context.beginPath();
      context.moveTo(p1.x, p1.y);
      context.quadraticCurveTo(p2.x, p2.y, p3.x, p3.y);
      context.stroke();
  };

    var lastX, grass = [], context = document.getElementById('canvas').getContext('2d');

    function updateGraphics(time) {
      window.requestAnimationFrame(updateGraphics);

      wind = 0.95*wind + 0.05*(POWER_MOUSE_WIND*windInput + POWER_RANDOM_WIND*Math.random() - POWER_RANDOM_WIND/2);
      windInput = 0;
      world.SetGravity(new B2Vec2(wind, -10));

      physicalObjects.forEach(function(obj) { if (obj.update) obj.update(time); });
      world.Step(1/60, 8, 3);
      world.ClearForces();

      context.clearRect(0, 0, context.canvas.width, context.canvas.height);
      context.save();
      context.translate(context.canvas.width/2, context.canvas.height/2);
      context.scale(context.canvas.width/20, -context.canvas.width/20);
      grass.forEach(function (o) { o.draw(context); });
      context.restore();
    }

    document.getElementsByTagName('body')[0].addEventListener("mousemove", function (e) {
      windInput = Math.abs(lastX - e.x) < 200? 0.2*(e.x - lastX) : 0;
      lastX = e.x;
    });

    var W = 8;
    for (var i = 0; i < STRAW_COUNT; i++) {
      grass.push(new Grass(new B2Vec2(W*(i/(STRAW_COUNT-1))-W/2, -1)));
    }

    window.requestAnimationFrame(updateGraphics);
})();

Answer 2

挥舞草算法

<强>更新

我做了简化更新，以更好地满足我认为您的要求。要使用鼠标，您只需计算鼠标点和应变根之间的角度，并在更新中将其用于新角度。

我采用了一种简单的鼠标移动敏感方法，使菌株“指向”鼠标，但您可以将随机角度添加到此作为增量等等。您需要的一切都如代码中所述 - 根据需要进行调整。

新小提琴（基于之前的一些修改）：
http://jsfiddle.net/AbdiasSoftware/yEwGc/

enter image description here

Grass simulation snaphot - 150 strains 图像显示150个菌株被模拟。

草模拟演示：
http://jsfiddle.net/AbdiasSoftware/5z89V/

这将产生一个看起来很逼真的草地。该演示有70个草渲染（在Chrome中最好用，或者只是降低Firefox的数量）。

代码相当简单。它由一个主要对象（grassObj）组成，它包含几何图形以及计算角度，线段，运动等的函数。我将在下面详细说明。

首先由函数全局访问的一些内容：

var numOfGrass = 70,  /// number of grass strains
    grass,

    /// get canvas context
    ctx = canvas.getContext('2d'),
    w = canvas.width,
    h = canvas.height,

    /// we use an animated image for the background
    /// The image also clears the canvas for each loop call
    /// I rendered the clouds in a 3D software.
    img = document.createElement('img'),
    ix = 0,  /// background image position
    iw = -1; /// used for with and initial for flag

    /// load background image, use it whenever it's ready
    img.onload = function() {iw = this.width}
    img.src = 'http://i.imgur.com/zzjtzG7.jpg';

心脏 - 草地

上面提到的主要对象是grassObj：

function grassObj(x, y, seg1, seg2, maxAngle) {

    /// exposed properties we need for rendering
    this.x = x;        /// bottom position of grass
    this.y = y;
    this.seg1 = seg1;  /// segments of grass
    this.seg2 = seg2; 
    this.gradient = getGradient(Math.random() * 50 + 50, 100 * Math.random() + 170);

    this.currentAngle; ///current angle that will be rendered

    /// internals used for calculating new angle, goal, difference and speed
    var counter,       /// counter between 0-1 for ease-in/out
        delta,         /// random steps in the direction goal rel. c.angle.
        angle,         /// current angle, does not change until goal is reached
        diff,          /// diff between goal and angle
        goal = getAngle();

    /// internal: returns an angel between 0 and maxAngle
    function getAngle() {
        return maxAngle * Math.random();
    }

    /// ease in-out function
    function easeInOut(t) {
        return t < 0.5 ? 4 * t * t * t : (t-1) * (2 * t - 2) * (2 * t - 2) + 1;
    }

    /// sets a new goal for grass to move to. Does the main calculations
    function newGoal() {
        angle = goal;        /// set goal as new angle when reached
        this.currentAngle = angle;
        goal = getAngle();   /// get new goal
        diff = goal - angle; /// calc diff
        counter = 0;         /// reset counter

        delta = (4 * Math.random() + 1) / 100;
    }

    /// creates a gradient for this grass to increase realism
    function getGradient(min, max) {

        var g = ctx.createLinearGradient(0, 0, 0, h);
        g.addColorStop(1,   'rgb(0,' + parseInt(min) + ', 0)');
        g.addColorStop(0,   'rgb(0,' + parseInt(max) + ', 0)');

        return g;
    }

    /// this is called from animation loop. Counts and keeps tracks of 
    /// current position and calls new goal when current goal is reached
    this.update = function() {

        /// count from 0 to 1 with random delta value   
        counter += delta;

        /// if counter passes 1 then goal is reached -> get new goal
        if (counter > 1) {
            newGoal();
            return;
        }

        /// ease in/out function
        var t = easeInOut(counter);

        /// update current angle for render
        this.currentAngle = angle + t * diff;
    }

    /// init
    newGoal();

    return this;
}

草发生器

我们呼叫makeGrass以随机位置，随机高度和随机段生成草。调用函数时要绘制草数，填充画布的宽度和高度以及百分比变化变量（0 - 1浮点数）。

单草总共只有四个点。两个中间点分布在总高度的1/3和2/3左右，并且断裂模式略有变化。渲染时的点，使用具有完全张力的基本样条曲线更平滑，使草看起来更光滑。

function makeGrass(numOfGrass, width, height, hVariation) {

    /// setup variables
    var x, y, seg1, seg2, angle,
        hf = height * hVariation,  /// get variation
        i = 0,
        grass = [];                /// array to hold the grass

    /// generate grass
    for(; i < numOfGrass; i++) {

        x = width * Math.random();        /// random x position
        y = height - hf * Math.random();  /// random height

        /// break grass into 3 segments with random variation
        seg1 = y / 3 + y * hVariation * Math.random() * 0.1;
        seg2 = (y / 3 * 2) + y * hVariation * Math.random() * 0.1;

        grass.push(new grassObj(x, y, seg1, seg2, 15 * Math.random() + 50));
}

    return grass;
}

渲染

渲染功能只是遍历对象并更新当前几何体：

function renderGrass(ctx, grass) {

    /// local vars for animation
    var len = grass.length,
        i = 0,
        gr, pos, diff, pts, x, y;

    /// renders background when loaded
    if (iw > -1) {
        ctx.drawImage(img, ix--, 0);
        if (ix < -w) {
            ctx.drawImage(img, ix + iw, 0);
        }
        if (ix <= -iw) ix = 0;
    } else {
        ctx.clearRect(0, 0, w, h);
    }

    /// loops through the grass object and renders current state
    for(; gr = grass[i]; i++) {

        x = gr.x;
        y = gr.y;

        ctx.beginPath();

        /// calculates the end-point based on length and angle
        /// Angle is limited [0, 60] which we add 225 deg. to get
        /// it upwards. Alter 225 to make grass lean more to a side.
        pos = lineToAngle(ctx, x, h, y, gr.currentAngle + 225);

        /// diff between end point and root point
        diff = (pos[0] - x)

        pts = [];

        /// starts at bottom, goes to top middle and then back
        /// down with a slight offset to make the grass

        pts.push(x); /// first couple at bottom
        pts.push(h);

        /// first segment 1/4 of the difference
        pts.push(x + (diff / 4));
        pts.push(h - gr.seg1);

        /// second segment 2/3 of the difference
        pts.push(x + (diff / 3 * 2));
        pts.push(h - gr.seg2);

        pts.push(pos[0]);    /// top point
        pts.push(pos[1]);

        /// re-use previous data, but go backward down to root again
        /// with a slight offset
        pts.push(x + (diff / 3 * 2) + 10);
        pts.push(h - gr.seg2);

        pts.push(x + (diff / 4) + 12);
        pts.push(h - gr.seg1 + 10);

        pts.push(x + 15); /// end couple at bottom
        pts.push(h);

        /// smooth points (extended context function, see demo)
        ctx.curve(pts, 0.8, 5);

        ctx.closePath();

        /// fill grass with its gradient
        ctx.fillStyle = gr.gradient;
        ctx.fill();
    }
}

动画

我们为所有内容制作动画的主循环：

function animate() {

    /// update each grass objects
    for(var i = 0;i < grass.length; i++) grass[i].update();            

    /// render them
    renderGrass(ctx, grass);

    /// loop
    requestAnimationFrame(animate);
}

这就是这个版本的全部内容。

Answer 3

<强>该死！晚到晚会......

但是这里有很多简洁的答案 - 我正在全力以赴！

无论如何，这是我的想法：

enter image description here

这是代码和小提琴：http://jsfiddle.net/m1erickson/MJjHz/

<!doctype html>
<html>
  <head>

    <link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
    <script src="http://code.jquery.com/jquery-1.9.1.js"></script>
    <script src="http://code.jquery.com/ui/1.10.1/jquery-ui.js"></script>

    <style>
      body { font-family: arial; padding:15px; }
      canvas { border: 1px solid red;}
      input[type="text"]{width:35px;}
    </style>

  </head>
  <body>
      <p>Move mouse across hairs</p>
      <canvas height="100" width="250" id="canvas"></canvas>
  <script>

      $(function() {

        var canvas=document.getElementById("canvas");
        var ctx = canvas.getContext("2d");
        var canvasOffset=$("#canvas").offset();
        var offsetX=canvasOffset.left;
        var offsetY=canvasOffset.top;

        var cHeight=canvas.height;
        var showControls=false;
        var lastMouseX=0;

        // preset styling CONSTANTS
        var SWAY=.55;     // max endpoint sway from center 
        var C1Y=.40;      // fixed Y of cp#1
        var C2SWAY=.20    // max cp#2 sway from center
        var C2Y=.75;      // fixed Y of cp#2
        var YY=20;        // max height of ellipse at top of hair
        var PIPERCENT=Math.PI/100;

        var hairs=[];

        // create hairs
        var newHairX=40;
        var hairCount=20;
        for(var i=0;i<hairCount;i++){
            var randomLength=50+parseInt(Math.random()*5);
            addHair(newHairX+(i*8),randomLength);
        }

        function addHair(x,length){
            hairs.push({
                x:x,
                length:length,
                left:0,
                right:0,
                top:0,
                s:{x:0,y:0},
                c1:{x:0,y:0},
                c2:{x:0,y:0},
                e:{x:0,y:0},
                isInMotion:false,
                currentX:0
            });
        }

        for(var i=0;i<hairs.length;i++){
            var h=hairs[i];
            setHairPointsFixed(h);
            setHairPointsPct(h,50);
            draw(h);
        }

        function setHairPointsFixed(h){
            h.s.x   = h.x;
            h.s.y   = cHeight;
            h.c1.x  = h.x;
            h.c1.y  = cHeight-h.length*C1Y;
            h.c2.y  = cHeight-h.length*C2Y;
            h.top   = cHeight-h.length;
            h.left  = h.x-h.length*SWAY;
            h.right = h.x+h.length*SWAY;
        }


        function setHairPointsPct(h,pct){
            // endpoint
            var a=Math.PI+PIPERCENT*pct;
            h.e.x  = h.x - ((h.length*SWAY)*Math.cos(a));
            h.e.y  = h.top + (YY*Math.sin(a));
            // controlpoint#2
            h.c2.x = h.x + h.length*(C2SWAY*2*pct/100-C2SWAY);
        }

        //////////////////////////////

        function handleMouseMove(e){
          mouseX=parseInt(e.clientX-offsetX);
          mouseY=parseInt(e.clientY-offsetY);

          // draw this frame based on mouse moves
          ctx.clearRect(0,0,canvas.width,canvas.height);
          for(var i=0;i<hairs.length;i++){
              hairMoves(hairs[i],mouseX,mouseY);
          }

          lastMouseX=mouseX;
        }
        $("#canvas").mousemove(function(e){handleMouseMove(e);});



        function hairMoves(h,mouseX,mouseY){

          // No hair movement if not touching hair
          if(mouseY<cHeight-h.length-YY){
              if(h.isInMotion){
                  h.isInMotion=false;
                  setHairPointsPct(h,50);
              }
              draw(h);
              return;
          }

          // No hair movement if too deep in hair
          if(mouseY>h.c1.y){
              draw(h);
              return;
          }

          //
          var pct=50;
          if(mouseX>=h.left && mouseX<=h.right){

              if(h.isInMotion){

                  var pct=-(mouseX-h.right)/(h.right-h.left)*100;
                  setHairPointsPct(h,pct);
                  draw(h);

              }else{

                  // if hair is at rest 
                  // but mouse has just contacted hair
                  // set hair in motion
                  if(   (lastMouseX<=h.x && mouseX>=h.x )
                      ||(lastMouseX>=h.x && mouseX<=h.x )
                  ){
                      h.isInMotion=true;
                      var pct=-(mouseX-h.right)/(h.right-h.left)*100;
                  }
                  setHairPointsPct(h,pct);
                  draw(h);

              }

          }else{
              if(h.isInMotion){
                  h.isInMotion=false;
                  setHairPointsPct(h,50);
              };
              draw(h);
          }

        }


        function dot(pt,color){
            ctx.beginPath();
            ctx.arc(pt.x,pt.y,5,0,Math.PI*2,false);
            ctx.closePath();
            ctx.fillStyle=color;
            ctx.fill();
        }


        function draw(h){

            ctx.beginPath();
            ctx.moveTo(h.s.x,h.s.y);
            ctx.bezierCurveTo(h.c1.x,h.c1.y,h.c2.x,h.c2.y,h.e.x,h.e.y);
            ctx.strokeStyle="orange";
            ctx.lineWidth=3;
            ctx.stroke();

            if(showControls){
                dot(h.s,"green");
                dot(h.c1,"red");
                dot(h.c2,"blue");
                dot(h.e,"purple");

                ctx.beginPath();
                ctx.rect(h.left,h.top-YY,(h.right-h.left),h.length*(1-C1Y)+YY)
                ctx.lineWidth=1;
                ctx.strokeStyle="lightgray";
                ctx.stroke();
            }

        }


    });
    </script>

  </body>   
</html>

Answer 4

这是一个简单的头发模拟，似乎是你正在寻找的。基本思想是绘制贝塞尔曲线（在这种情况下，我使用两条曲线来为头发提供厚度）。曲线将具有基部，弯曲点和尖端。我将弯曲点设置在头发的中间位置。为了响应鼠标的移动，头发的尖端将围绕头发的基部轴线旋转。

将此代码放在canvas元素声明下面的脚本标记中。

    function Point(x, y) {
        this.x = x;
        this.y = y;
    }

    function Hair( )  {
        this.height = 100;   // hair height
        this.baseWidth = 3;    // hair base width.
        this.thickness = 1.5; // hair thickness
        this.points = {};

        this.points.base1 = new Point(Math.random()*canvas.width, canvas.height);

        // The point at which the hair will bend. I set it to the middle of the hair, but you can adjust this.
        this.points.bendPoint1 = new Point(this.points.base1.x-this.thickness, this.points.base1.y - this.height / 2)

        this.points.bendPoint2 = new Point(this.points.bendPoint1.x, this.points.bendPoint1.y-this.thickness); // complement of bendPoint1 - we use this because the hair has thickness
        this.points.base2 = new Point(this.points.base1.x + this.baseWidth, this.points.base1.y) // complement of base1 - we use this because the hair has thickness
    }

    Hair.prototype.paint = function(mouseX, mouseY, direction) {    
        ctx.save();

        // rotate the the tip of the hair
        var tipRotationAngle = Math.atan(Math.abs(this.points.base1.y - mouseY)/Math.abs(this.points.base1.x - mouseX));

        // if the mouse is on the other side of the hair, adjust the angle
        if (mouseX < this.points.base1.x) {
            tipRotationAngle = Math.PI - tipRotationAngle;
        }

        // if the mouse isn't close enough to the hair, it shouldn't affect the hair
        if (mouseX < this.points.base1.x - this.height/2 || mouseX > this.points.base1.x + this.height/2 || mouseY < this.points.base1.y - this.height || mouseY > this.points.base1.y) {
            tipRotationAngle = Math.PI/2; // 90 degrees, which means the hair is straight
        }

        // Use the direction of the mouse to as a lazy way to simulate the direction the hair should bend.
        // Note that in real life, the direction that the hair should bend has nothing to do with the direction of motion. It actually depends on which side of the hair the force is being applied.
        // Figuring out which side of the hair the force is being applied is a little tricky, so I took this shortcut.
        // If you run your finger along a comb quickly, this approximation will work. However if you are in the middle of the comb and slowly change direction, you will notice that the force is still applied in the opposite direction of motion as you slowly back off the set of tines.
        if ((mouseX < this.points.base1.x && direction == 'right') || (mouseX > this.points.base1.x && direction == 'left')) {
            tipRotationAngle = Math.PI/2; // 90 degrees, which means the hair is straight
        }

        var tipPoint = new Point(this.points.base1.x + this.baseWidth + this.height*Math.cos(tipRotationAngle), this.points.base1.y - this.height*Math.sin(tipRotationAngle));

        ctx.beginPath();
        ctx.moveTo(this.points.base1.x, this.points.base1.y); // start at the base
        ctx.bezierCurveTo(this.points.base1.x, this.points.base1.y, this.points.bendPoint1.x, this.points.bendPoint1.y, tipPoint.x, tipPoint.y); // draw a curve to the tip of the hair
        ctx.bezierCurveTo(tipPoint.x, tipPoint.y, this.points.bendPoint2.x, this.points.bendPoint2.y, this.points.base2.x, this.points.base2.y); // draw a curve back down to the base using the complement points since the hair has thickness.
        ctx.closePath(); // complete the path so we have a shape that we can fill with color
        ctx.fillStyle='rgb(0,0,0)';
        ctx.fill();

        ctx.restore();
    }  

    // I used global variables to keep the example simple, but it is generally best to avoid using global variables
    window.canvas = document.getElementById('myCanvas');
    window.ctx = canvas.getContext('2d');
    ctx.fillStyle = 'rgb(200,255,255)'; // background color
    window.hair = [];
    window.prevClientX = 0;

    for (var i = 0; i < 100; i++) {
        hair.push(new Hair());
    }

    // initial draw
    ctx.fillRect(0,0,canvas.width,canvas.height); // clear canvas
    for (var i = 0; i < hair.length; i++) {
        hair[i].paint(0, 0, 'right');
    }

    window.onmousemove = function(e)    {
        ctx.fillRect(0,0,canvas.width,canvas.height); // clear canvas

        for (var i = 0; i < hair.length; i++) {
            hair[i].paint(e.clientX, e.clientY, e.clientX > window.prevClientX ? 'right' : 'left');
        }
        window.prevClientX = e.clientX;
    }

Answer 5

前一段时间制作this，可能对某些人有用。只需使用符合您意愿的值调整代码开头的变量：

...
Mheight = 1;
height = 33;
width = 17;
distance = 10;
randomness = 14;
angle = Math.PI / 2;
...

同样在http://lucasm0ta.github.io/JsGrass/

草像beziercurve上的平滑动画？

5 个答案:

挥舞草算法

心脏 - 草地

草发生器

渲染

动画