SOURCE

// -------------------------- utils -------------------------- //

var TAU = Math.PI * 2;

function extend( a, b ) {
  for ( var prop in b ) {
    a[ prop ] = b[ prop ];
  }
  return a;
}

function lerp( a, b, t ) {
  return ( b - a ) * t + a;
}

function modulo( num, div ) {
  return ( ( num % div ) + div ) % div;
}

// -------------------------- Vector3 -------------------------- //

function Vector3( position ) {
  this.set( position );
}

Vector3.prototype.set = function( pos ) {
  pos = Vector3.sanitize( pos );
  this.x = pos.x;
  this.y = pos.y;
  this.z = pos.z;
  return this;
};

Vector3.prototype.rotate = function( rotation ) {
  if ( !rotation ) {
    return;
  }
  this.rotateZ( rotation.z );
  this.rotateY( rotation.y );
  this.rotateX( rotation.x );
  return this;
};

Vector3.prototype.rotateZ = function( angle ) {
  rotateProperty( this, angle, 'x', 'y' );
};

Vector3.prototype.rotateX = function( angle ) {
  rotateProperty( this, angle, 'y', 'z' );
};

Vector3.prototype.rotateY = function( angle ) {
  rotateProperty( this, angle, 'x', 'z' );
};

function rotateProperty( vec, angle, propA, propB ) {
  if ( angle % TAU === 0 ) {
    return;
  }
  var cos = Math.cos( angle );
  var sin = Math.sin( angle );
  var a = vec[ propA ];
  var b = vec[ propB ];
  vec[ propA ] = a*cos - b*sin;
  vec[ propB ] = b*cos + a*sin;
}

Vector3.prototype.add = function( vec ) {
  if ( !vec ) {
    return;
  }
  vec = Vector3.sanitize( vec );
  this.x += vec.x;
  this.y += vec.y;
  this.z += vec.z;
  return this;
};

Vector3.prototype.multiply = function( vec ) {
  if ( !vec ) {
    return;
  }
  vec = Vector3.sanitize( vec );
  this.x *= vec.x;
  this.y *= vec.y;
  this.z *= vec.z;
  return this;
};

Vector3.prototype.lerp = function( vec, t ) {
  this.x = lerp( this.x, vec.x, t );
  this.y = lerp( this.y, vec.y, t );
  this.z = lerp( this.z, vec.z, t );
  return this;
};

// ----- utils ----- //

// add missing properties
Vector3.sanitize = function( vec ) {
  vec = vec || {};
  vec.x = vec.x || 0;
  vec.y = vec.y || 0;
  vec.z = vec.z || 0;
  return vec;
};

// -------------------------- PathAction -------------------------- //

function PathAction( method, points, previousPoint ) {
  this.method = method;
  this.points = points.map( mapVectorPoint );
  this.renderPoints = points.map( mapVectorPoint );
  this.previousPoint = previousPoint;
  this.endRenderPoint = this.renderPoints[ this.renderPoints.length - 1 ];
  // arc actions come with previous point & corner point
  // but require bezier control points
  if ( method == 'arc' ) {
    this.controlPoints = [ new Vector3(), new Vector3() ];
  }
}

function mapVectorPoint( point ) {
  return new Vector3( point );
}

PathAction.prototype.reset = function() {
  // reset renderPoints back to orignal points position
  var points = this.points;
  this.renderPoints.forEach( function( renderPoint, i ) {
    var point = points[i];
    renderPoint.set( point );
  });
};

PathAction.prototype.transform = function( translation, rotation, scale ) {
  this.renderPoints.forEach( function( renderPoint ) {
    renderPoint.multiply( scale );
    renderPoint.rotate( rotation );
    renderPoint.add( translation );
  });
};

PathAction.prototype.render = function( ctx ) {
  this[ this.method ]( ctx );
};

PathAction.prototype.move = function( ctx ) {
  var point = this.renderPoints[0];
  ctx.moveTo( point.x, point.y );
};

PathAction.prototype.line = function( ctx ) {
  var point = this.renderPoints[0];
  ctx.lineTo( point.x, point.y );
};

PathAction.prototype.bezier = function( ctx ) {
  var cp0 = this.renderPoints[0];
  var cp1 = this.renderPoints[1];
  var end = this.renderPoints[2];
  ctx.bezierCurveTo( cp0.x, cp0.y, cp1.x, cp1.y, end.x, end.y );
};

PathAction.prototype.arc = function( ctx ) {
  var prev = this.previousPoint;
  var corner = this.renderPoints[0];
  var end = this.renderPoints[1];
  var cp0 = this.controlPoints[0];
  var cp1 = this.controlPoints[1];
  cp0.set( prev ).lerp( corner, 9/16 );
  cp1.set( end ).lerp( corner, 9/16 );
  ctx.bezierCurveTo( cp0.x, cp0.y, cp1.x, cp1.y, end.x, end.y );
};

// -------------------------- Shape -------------------------- //

function Shape( options ) {
  this.create( options );
}

Shape.prototype.create = function( options ) {
  // default
  extend( this, Shape.defaults );
  // set options
  setOptions( this, options );

  this.updatePathActions();

  // transform
  this.translate = Vector3.sanitize( this.translate );
  this.rotate = Vector3.sanitize( this.rotate );
  this.scale = extend( { x: 1, y: 1, z: 1 }, this.scale );
  this.scale = Vector3.sanitize( this.scale );
  // children
  this.children = [];
  if ( this.addTo ) {
    this.addTo.addChild( this );
  }
};

Shape.defaults = {
  stroke: true,
  fill: false,
  color: 'black',
  lineWidth: 1,
  closed: true,
  rendering: true,
  path: [ {} ],
};

var optionKeys = Object.keys( Shape.defaults ).concat([
  'rotate',
  'translate',
  'scale',
  'addTo',
  'width',
  'height',
]);

function setOptions( shape, options ) {
  for ( var key in options ) {
    if ( optionKeys.includes( key ) ) {
      shape[ key ] = options[ key ];
    }
  }
}

var actionNames = [
  'move',
  'line',
  'bezier',
  'arc',
];

// parse path into PathActions
Shape.prototype.updatePathActions = function() {
  var previousPoint;
  this.pathActions = this.path.map( function( pathPart, i ) {
    // pathPart can be just vector coordinates -> { x, y, z }
    // or path instruction -> { arc: [ {x0,y0,z0}, {x1,y1,z1} ] }
    var keys = Object.keys( pathPart );
    var method = keys[0];
    var points = pathPart[ method ];
    var isInstruction = keys.length === 1 && actionNames.includes( method ) &&
      Array.isArray( points );

    if ( !isInstruction ) {
      method = 'line';
      points = [ pathPart ];
    }

    // first action is always move
    method = i === 0 ? 'move' : method;
    // arcs require previous last point
    var pathAction = new PathAction( method, points, previousPoint );
    // update previousLastPoint
    previousPoint = pathAction.endRenderPoint;
    return pathAction;
  });
};

Shape.prototype.addChild = function( shape ) {
  this.children.push( shape );
};

// ----- update ----- //

Shape.prototype.update = function() {
  // update self
  this.reset();
  // update children
  this.children.forEach( function( child ) {
    child.update();
  });
  this.transform( this.translate, this.rotate, this.scale );
};

Shape.prototype.reset = function() {
  // reset pathAction render points
  this.pathActions.forEach( function( pathAction ) {
    pathAction.reset();
  });
};

Shape.prototype.transform = function( translation, rotation, scale ) {
  // transform points
  this.pathActions.forEach( function( pathAction ) {
    pathAction.transform( translation, rotation, scale );
  });
  // transform children
  this.children.forEach( function( child ) {
    child.transform( translation, rotation, scale );
  });
};

Shape.prototype.updateSortValue = function() {
  var sortValueTotal = 0;
  this.pathActions.forEach( function( pathAction ) {
    sortValueTotal += pathAction.endRenderPoint.z;
  });
  // average sort value of all points
  // def not geometrically correct, but works for me
  this.sortValue = sortValueTotal / this.pathActions.length;
};

// ----- render ----- //

Shape.prototype.render = function( ctx ) {
  var length = this.pathActions.length;
  if ( !this.rendering || !length ) {
    return;
  }
  var isDot = length == 1;
  if ( isDot ) {
    this.renderDot( ctx );
  } else {
    this.renderPath( ctx );
  }
};

// Safari does not render lines with no size, have to render circle instead
Shape.prototype.renderDot = function( ctx ) {
  ctx.fillStyle = this.color;
  var point = this.pathActions[0].endRenderPoint;
  ctx.beginPath();
  var radius = this.lineWidth/2;
  ctx.arc( point.x, point.y, radius, 0, TAU );
  ctx.fill();
};

Shape.prototype.renderPath = function( ctx ) {
  // set render properties
  ctx.fillStyle = this.color;
  ctx.strokeStyle = this.color;
  ctx.lineWidth = this.lineWidth;

  // render points
  ctx.beginPath();
  this.pathActions.forEach( function( pathAction ) {
    pathAction.render( ctx );
  });
  var isTwoPoints = this.pathActions.length == 2 &&
    this.pathActions[1].method == 'line';
  if ( !isTwoPoints && this.closed ) {
    ctx.closePath();
  }
  if ( this.stroke ) {
    ctx.stroke();
  }
  if ( this.fill ) {
    ctx.fill();
  }
};

// return Array of self & all child shapes
Shape.prototype.getShapes = function() {
  var shapes = [ this ];
  this.children.forEach( function( child ) {
    var childShapes = child.getShapes();
    shapes = shapes.concat( childShapes );
  });
  return shapes;
};

Shape.prototype.copy = function( options ) {
  // copy options
  var shapeOptions = {};
  optionKeys.forEach( function( key ) {
    shapeOptions[ key ] = this[ key ];
  }, this );
  // add set options
  setOptions( shapeOptions, options );
  var ShapeClass = this.constructor;
  return new ShapeClass( shapeOptions );
};


// -------------------------- Ellipse -------------------------- //

function Ellipse( options ) {
  options = this.setPath( options );
  // always keep open
  // fixes overlap bug when lineWidth is greater than radius
  options.closed = false;
  this.create( options );
}

Ellipse.prototype = Object.create( Shape.prototype );
Ellipse.prototype.constructor = Ellipse;

Ellipse.prototype.setPath = function( options ) {
  var w = options.width/2;
  var h = options.height/2;
  options.path = [
    { x: 0, y: -h },
    { arc: [ // top right
      { x: w, y: -h },
      { x: w, y: 0 },
    ]},
    { arc: [ // bottom right
      { x: w, y: h },
      { x: 0, y: h },
    ]},
    { arc: [ // bottom left
      { x: -w, y: h },
      { x: -w, y: 0 },
    ]},
    { arc: [ // bottom left
      { x: -w, y: -h },
      { x: 0, y: -h },
    ]},
  ];
  return options;
};

// -------------------------- Group -------------------------- //

function Group( options ) {
  this.create( options );
}

Group.prototype.create = function( options ) {
  // set options
  setGroupOptions( this, options );

  // transform
  this.translate = Vector3.sanitize( this.translate );
  this.rotate = Vector3.sanitize( this.rotate );
  // children
  this.children = [];
  if ( this.addTo ) {
    this.addTo.addChild( this );
  }
};

var groupOptionKeys = [
  'rotate',
  'translate',
  'addTo',
];

function setGroupOptions( shape, options ) {
  for ( var key in options ) {
    if ( groupOptionKeys.includes( key ) ) {
      shape[ key ] = options[ key ];
    }
  }
}


Group.prototype.addChild = function( shape ) {
  this.children.push( shape );
};

// ----- update ----- //

Group.prototype.update = function() {
  // update self
  this.reset();
  // update children
  this.children.forEach( function( child ) {
    child.update();
  });
  this.transform( this.translate, this.rotate );
};

Group.prototype.reset = function() {};

Group.prototype.transform = function( translation, rotation ) {
  // transform children
  this.children.forEach( function( child ) {
    child.transform( translation, rotation );
  });
};

Group.prototype.updateSortValue = function() {
  var sortValueTotal = 0;
  this.children.forEach( function( child ) {
    child.updateSortValue();
    sortValueTotal += child.sortValue;
  });
  // TODO sort children?
  // average sort value of all points
  // def not geometrically correct, but works for me
  this.sortValue = sortValueTotal / this.children.length;
};

// ----- render ----- //

Group.prototype.render = function( ctx ) {
  this.children.forEach( function( child ) {
    child.render( ctx );
  });
};

// do not include children, group handles rendering & sorting internally
Group.prototype.getShapes = function() {
  return [ this ];
};

// -------------------------- Dragger -------------------------- //

// quick & dirty drag event stuff
// messes up if multiple pointers/touches

// event support, default to mouse events
var downEvent = 'mousedown';
var moveEvent = 'mousemove';
var upEvent = 'mouseup';
if ( window.PointerEvent ) {
  // PointerEvent, Chrome
  downEvent = 'pointerdown';
  moveEvent = 'pointermove';
  upEvent = 'pointerup';
} else if ( 'ontouchstart' in window ) {
  // Touch Events, iOS Safari
  downEvent = 'touchstart';
  moveEvent = 'touchmove';
  upEvent = 'touchend';
}

function noop() {}

function Dragger( options ) {
  this.startElement = options.startElement;
  this.onPointerDown = options.onPointerDown || noop;
  this.onPointerMove = options.onPointerMove || noop;
  this.onPointerUp = options.onPointerUp || noop;
  
  this.startElement.addEventListener( downEvent, this );
}

Dragger.prototype.handleEvent = function( event ) {
  var method = this[ 'on' + event.type ];
  if ( method ) {
    method.call( this, event );
  }
};

Dragger.prototype.onmousedown =
Dragger.prototype.onpointerdown = function( event ) {
  this.pointerDown( event, event );
};

Dragger.prototype.ontouchstart = function( event ) {
  this.pointerDown( event, event.changedTouches[0] );
};

Dragger.prototype.pointerDown = function( event, pointer ) {
  event.preventDefault();
  this.dragStartX = pointer.pageX;
  this.dragStartY = pointer.pageY;
  window.addEventListener( moveEvent, this );
  window.addEventListener( upEvent, this );
  this.onPointerDown( pointer );
};

Dragger.prototype.ontouchmove = function( event ) {
  // HACK, moved touch may not be first
  this.pointerMove( event, event.changedTouches[0] );
};

Dragger.prototype.onmousemove =
Dragger.prototype.onpointermove = function( event ) {
  this.pointerMove( event, event );
};

Dragger.prototype.pointerMove = function( event, pointer ) {
  event.preventDefault();
  var moveX = pointer.pageX - this.dragStartX;
  var moveY = pointer.pageY - this.dragStartY;
  this.onPointerMove( pointer, moveX, moveY );
};

Dragger.prototype.onmouseup = 
Dragger.prototype.onpointerup =
Dragger.prototype.ontouchend =
Dragger.prototype.pointerUp = function( event ) {
  window.removeEventListener( moveEvent, this );
  window.removeEventListener( upEvent, this );
  this.onPointerUp( event );
};

// -------------------------- demo -------------------------- //

var canvas = document.querySelector('canvas');
var ctx = canvas.getContext('2d');
var w = 80;
var h = 80;
var minWindowSize = Math.min( window.innerWidth, window.innerHeight );
var zoom = Math.min( 7, Math.floor( minWindowSize / w ) );
var pixelRatio = window.devicePixelRatio || 1;
zoom *= pixelRatio;
var canvasWidth = canvas.width = w * zoom;
var canvasHeight = canvas.height = h * zoom;
// set canvas screen size
if ( pixelRatio > 1 ) {
  canvas.style.width = canvasWidth / pixelRatio + 'px';
  canvas.style.height = canvasHeight / pixelRatio + 'px';
}

var isRotating = true;

// colors
var pink = '#F8B';
var blush = '#F5A';
var black = '#333';
var shoe = '#D03';
var red = '#E10';
var yellow = '#FD0';

var camera = new Shape({
  rendering: false,
});

// -- illustration shapes --- //

var body = new Shape({
  lineWidth: 22,
  translate: { y: 11 },
  rotate: { x: -0.3, z: 0.1 },
  addTo: camera,
  color: pink,
});

var face = new Shape({
  rendering: false,
  translate: { z: -10.5 },
  addTo: body,
});

[ -1, 1 ].forEach( function( xSide ) {
  var eyeGroup = new Group({
    addTo: face,
    translate: { x: 2.4*xSide, y: -2 },
    rotate: { x: -0.1 },
  });
  // eye
  new Ellipse({
    width: 1.4,
    height: 5.5,
    addTo: eyeGroup,
    lineWidth: 1,
    color: black,
    fill: true,
  });
  // eye highlight
  new Ellipse({
    width: 1,
    height: 2,
    addTo: eyeGroup,
    translate: { y: -1.5, z: -0.5 },
    lineWidth: 0.5,
    color: '#FFF',
    fill: true,
  });

  // cheek holder
  var cheekHolder = new Shape({
    rendering: false,
    addTo: body,
    rotate: { y: 0.6*xSide },
  });

  new Ellipse({
    width: 2.5,
    height: 1,
    translate: { y: 1, z: -10.5 },
    addTo: cheekHolder,
    color: blush,
    lineWidth: 1,
  });

});

// mouth
new Shape({
  path: [
    { x: 0, y: 0 },
    { bezier: [
      { x: 1.1, y: 0 },
      { x: 1.1, y: 0.2 },
      { x: 1.1, y: 0.5 },
    ]},
    { bezier: [
      { x: 1.1, y: 1.1 },
      { x: 0.2, y: 1.8 },
      { x: 0, y: 1.8 },
    ]},
    { bezier: [
      { x: -0.2, y: 1.8 },
      { x: -1.1, y: 1.1 },
      { x: -1.1, y: 0.5 },
    ]},
    { bezier: [
      { x: -1.1, y: 0.2 },
      { x: -1.1, y: 0 },
      { x: 0, y: 0 },
    ]},
  ],
  addTo: face,
  translate: { y: 2, z: 0.5 },
  lineWidth: 1,
  color: shoe,
  fill: true,
});

var rightArm = new Shape({
  path: [
    { y: 0 },
    { y: -7 },
  ],
  addTo: body,
  translate: { x: -6, y: -4, z: 0 },
  color: pink,
  lineWidth: 7,
});

// left arm
rightArm.copy({
  path: [
    { x: 0 },
    { x: 6 },
  ],
  translate: { x: 6, y: -2, z: 0 },
});

// right foot
var rightFoot = new Shape({
  path: [
    { x: 0, y: -2 },
    { arc: [
      { x: 2, y: -2 },
      { x: 2, y: 0 },
    ]},
    { arc: [
      { x: 2, y: 5 },
      { x: 0, y: 5 },
    ]},
    { arc: [
      { x: -2, y: 5 },
      { x: -2, y: 0 },
    ]},
    { arc: [
      { x: -2, y: -2 },
      { x: 0, y: -2 },
    ]},
  ],
  addTo: body,
  translate: { x: -1, y: 9, z: 9 },
  rotate: { z: -0.2 },
  lineWidth: 6,
  color: shoe,
  fill: true,
  closed: false,
});

rightFoot.copy({
  translate: { x: 9.5, y: 6, z: 6 },
  rotate: { z: -1.1, y: -0.8 }
});

// ----- umbrella ----- //

// umbrella rod
var umbrella = new Shape({
  path: [
    { y: 0 },
    { y: 22 },
  ],
  addTo: rightArm,
  translate: { y: -33, z: -2 },
  rotate: { y: -0.5 },
  color: yellow,
  lineWidth: 1,
});

// star
var starPath = ( function() {
  var path = [];
  var starRadiusA = 3;
  var starRadiusB = 1.7;
  for ( var i=0; i<10; i++ ) {
    var radius = i % 2 ? starRadiusA : starRadiusB;
    var angle = TAU * i/10 + TAU/4;
    var point = {
      x: Math.cos( angle ) * radius,
      y: Math.sin( angle ) * radius,
    };
    path.push( point );
  }
  return path;
})();
// star shape
var star = new Shape({
  path: starPath,
  addTo: umbrella,
  translate: { y: -4.5 },
  lineWidth: 2,
  color: yellow,
  fill: true,
});

// umbrella handle
new Shape({
  path: [
    { z: 0, y: 0 },
    { z: 0, y: 1 },
    { arc: [
      { z: 0, y: 4 },
      { z: -3, y: 4 },
    ]},
    { arc: [
      { z: -6, y: 4 },
      { z: -6, y: 1 },
    ]},
  ],
  addTo: umbrella,
  translate: { y: 23 },
  lineWidth: 2,
  color: '#37F',
  closed: false,
});

// umbrella shield panels
( function() {
  var umbPanelX = 14 * Math.sin( TAU/24 );
  var umbPanelZ = 14 * Math.cos( TAU/24 );
  for ( var i=0; i<12; i++ ) {
    var colorSide = Math.floor( i / 2 ) % 2;
    new Shape({
      path: [
        { x: 0, y: 0, z: 0 },
        { arc: [
          { x: -umbPanelX, y: 0, z: -umbPanelZ },
          { x: -umbPanelX, y: 14, z: -umbPanelZ },
        ]},
        { x: umbPanelX, y: 14, z: -umbPanelZ },
        { arc: [
          { x: umbPanelX, y: 0, z: -umbPanelZ },
          { x: 0, y: 0, z: 0 },
        ]},
      ],
      addTo: umbrella,
      rotate: { y: TAU/12 * i },
      lineWidth: 1,
      color: colorSide ? red : 'white',
      fill: true,
    });
  }
})();

// ----- floater stars ----- //

( function() {
  for ( var i=0; i < 6; i++ ) {
    var starHolder = new Shape({
      rendering: false,
      addTo: umbrella,
      translate: { y: 10 },
      rotate: { y: TAU/6 * i + TAU/24 },
    });
    star.copy({
      addTo: starHolder,
      translate: { z: 28 },
    });
  }
})();

// -----  ----- //

var shapes = camera.getShapes();

// -- animate --- //

function animate() {
  update();
  render();
  requestAnimationFrame( animate );
}

animate();

// -- update -- //

function update() {
  camera.rotate.y += isRotating ? +TAU/150 : 0;

  // rotate
  camera.update();
  shapes.forEach( function( shape ) {
    shape.updateSortValue();
  });
  // perspective sort
  shapes.sort( function( a, b ) {
    return b.sortValue - a.sortValue;
  });
}

// -- render -- //

function render() {
  ctx.clearRect( 0, 0, canvasWidth, canvasHeight );
  ctx.lineCap = 'round';
  ctx.lineJoin = 'round';

  ctx.save();
  ctx.scale( zoom, zoom );
  ctx.translate( w/2, h/2 );

  shapes.forEach( function( shape ) {
    shape.render( ctx );
  });

  ctx.restore();
}

// ----- inputs ----- //

// click drag to rotate
var dragStartAngleX, dragStartAngleY;

new Dragger({
  startElement: canvas,
  onPointerDown: function() {
    isRotating = false;
    dragStartAngleX = camera.rotate.x;
    dragStartAngleY = camera.rotate.y;
  },
  onPointerMove: function( pointer, moveX, moveY ) {
    var angleXMove = moveY / canvasWidth * TAU;
    var angleYMove = moveX / canvasWidth * TAU;
    camera.rotate.x = dragStartAngleX + angleXMove;
    camera.rotate.y = dragStartAngleY + angleYMove;
  },
});

<div class="container">
  <canvas></canvas>
  <p>鼠标点击拖动</p>
</div>

html { height: 100%; }

body {
  min-height: 100%;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #425;
  color: white;
  font-family: sans-serif;
  text-align: center;
}

canvas {
  display: block;
  margin: 0px auto 20px;
  cursor: move;
}