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//往后的先不研究
// cuon-matrix.js (c) 2012 kanda and matsuda
/** 
 * This is a class treating 4x4 matrix.
 * This class contains the function that is equivalent to OpenGL matrix stack.
 * The matrix after conversion is calculated by multiplying a conversion matrix from the right.
 * The matrix is replaced by the calculated result.
 */

/**
 * Constructor of Matrix4
 * If opt_src is specified, new matrix is initialized by opt_src.
 * Otherwise, new matrix is initialized by identity matrix.
 * @param opt_src source matrix(option)
 */
var Matrix4 = function(opt_src) {
  var i, s, d;
  if (opt_src && typeof opt_src === 'object' && opt_src.hasOwnProperty('elements')) {
    s = opt_src.elements;
    d = new Float32Array(16);
    for (i = 0; i < 16; ++i) {
      d[i] = s[i];
    }
    this.elements = d;
  } else {
    this.elements = new Float32Array([1,0,0,0, 0,1,0,0, 0,0,1,0, 0,0,0,1]);
  }
};

/**
 * Set the identity matrix.
 * @return this
 */
Matrix4.prototype.setIdentity = function() {
  var e = this.elements;
  e[0] = 1;   e[4] = 0;   e[8]  = 0;   e[12] = 0;
  e[1] = 0;   e[5] = 1;   e[9]  = 0;   e[13] = 0;
  e[2] = 0;   e[6] = 0;   e[10] = 1;   e[14] = 0;
  e[3] = 0;   e[7] = 0;   e[11] = 0;   e[15] = 1;
  return this;
};

/**
 * Copy matrix.
 * @param src source matrix
 * @return this
 */
Matrix4.prototype.set = function(src) {
  var i, s, d;

  s = src.elements;
  d = this.elements;

  if (s === d) {
    return;
  }
    
  for (i = 0; i < 16; ++i) {
    d[i] = s[i];
  }

  return this;
};

/**
 * Multiply the matrix from the right.
 * @param other The multiply matrix
 * @return this
 */
Matrix4.prototype.concat = function(other) {
  var i, e, a, b, ai0, ai1, ai2, ai3;
  
  // Calculate e = a * b
  e = this.elements;
  a = this.elements;
  b = other.elements;
  
  // If e equals b, copy b to temporary matrix.
  if (e === b) {
    b = new Float32Array(16);
    for (i = 0; i < 16; ++i) {
      b[i] = e[i];
    }
  }
  
  for (i = 0; i < 4; i++) {
    ai0=a[i];  ai1=a[i+4];  ai2=a[i+8];  ai3=a[i+12];
    e[i]    = ai0 * b[0]  + ai1 * b[1]  + ai2 * b[2]  + ai3 * b[3];
    e[i+4]  = ai0 * b[4]  + ai1 * b[5]  + ai2 * b[6]  + ai3 * b[7];
    e[i+8]  = ai0 * b[8]  + ai1 * b[9]  + ai2 * b[10] + ai3 * b[11];
    e[i+12] = ai0 * b[12] + ai1 * b[13] + ai2 * b[14] + ai3 * b[15];
  }
  
  return this;
};
Matrix4.prototype.multiply = Matrix4.prototype.concat;

/**
 * Multiply the three-dimensional vector.
 * @param pos  The multiply vector
 * @return The result of multiplication(Float32Array)
 */
Matrix4.prototype.multiplyVector3 = function(pos) {
  var e = this.elements;
  var p = pos.elements;
  var v = new Vector3();
  var result = v.elements;

  result[0] = p[0] * e[0] + p[1] * e[4] + p[2] * e[ 8] + e[11];
  result[1] = p[0] * e[1] + p[1] * e[5] + p[2] * e[ 9] + e[12];
  result[2] = p[0] * e[2] + p[1] * e[6] + p[2] * e[10] + e[13];

  return v;
};

/**
 * Multiply the four-dimensional vector.
 * @param pos  The multiply vector
 * @return The result of multiplication(Float32Array)
 */
Matrix4.prototype.multiplyVector4 = function(pos) {
  var e = this.elements;
  var p = pos.elements;
  var v = new Vector4();
  var result = v.elements;

  result[0] = p[0] * e[0] + p[1] * e[4] + p[2] * e[ 8] + p[3] * e[12];
  result[1] = p[0] * e[1] + p[1] * e[5] + p[2] * e[ 9] + p[3] * e[13];
  result[2] = p[0] * e[2] + p[1] * e[6] + p[2] * e[10] + p[3] * e[14];
  result[3] = p[0] * e[3] + p[1] * e[7] + p[2] * e[11] + p[3] * e[15];

  return v;
};

/**
 * Transpose the matrix.
 * @return this
 */
Matrix4.prototype.transpose = function() {
  var e, t;

  e = this.elements;

  t = e[ 1];  e[ 1] = e[ 4];  e[ 4] = t;
  t = e[ 2];  e[ 2] = e[ 8];  e[ 8] = t;
  t = e[ 3];  e[ 3] = e[12];  e[12] = t;
  t = e[ 6];  e[ 6] = e[ 9];  e[ 9] = t;
  t = e[ 7];  e[ 7] = e[13];  e[13] = t;
  t = e[11];  e[11] = e[14];  e[14] = t;

  return this;
};

/**
 * Calculate the inverse matrix of specified matrix, and set to this.
 * @param other The source matrix
 * @return this
 */
Matrix4.prototype.setInverseOf = function(other) {
  var i, s, d, inv, det;

  s = other.elements;
  d = this.elements;
  inv = new Float32Array(16);

  inv[0]  =   s[5]*s[10]*s[15] - s[5] *s[11]*s[14] - s[9] *s[6]*s[15]
            + s[9]*s[7] *s[14] + s[13]*s[6] *s[11] - s[13]*s[7]*s[10];
  inv[4]  = - s[4]*s[10]*s[15] + s[4] *s[11]*s[14] + s[8] *s[6]*s[15]
            - s[8]*s[7] *s[14] - s[12]*s[6] *s[11] + s[12]*s[7]*s[10];
  inv[8]  =   s[4]*s[9] *s[15] - s[4] *s[11]*s[13] - s[8] *s[5]*s[15]
            + s[8]*s[7] *s[13] + s[12]*s[5] *s[11] - s[12]*s[7]*s[9];
  inv[12] = - s[4]*s[9] *s[14] + s[4] *s[10]*s[13] + s[8] *s[5]*s[14]
            - s[8]*s[6] *s[13] - s[12]*s[5] *s[10] + s[12]*s[6]*s[9];

  inv[1]  = - s[1]*s[10]*s[15] + s[1] *s[11]*s[14] + s[9] *s[2]*s[15]
            - s[9]*s[3] *s[14] - s[13]*s[2] *s[11] + s[13]*s[3]*s[10];
  inv[5]  =   s[0]*s[10]*s[15] - s[0] *s[11]*s[14] - s[8] *s[2]*s[15]
            + s[8]*s[3] *s[14] + s[12]*s[2] *s[11] - s[12]*s[3]*s[10];
  inv[9]  = - s[0]*s[9] *s[15] + s[0] *s[11]*s[13] + s[8] *s[1]*s[15]
            - s[8]*s[3] *s[13] - s[12]*s[1] *s[11] + s[12]*s[3]*s[9];
  inv[13] =   s[0]*s[9] *s[14] - s[0] *s[10]*s[13] - s[8] *s[1]*s[14]
            + s[8]*s[2] *s[13] + s[12]*s[1] *s[10] - s[12]*s[2]*s[9];

  inv[2]  =   s[1]*s[6]*s[15] - s[1] *s[7]*s[14] - s[5] *s[2]*s[15]
            + s[5]*s[3]*s[14] + s[13]*s[2]*s[7]  - s[13]*s[3]*s[6];
  inv[6]  = - s[0]*s[6]*s[15] + s[0] *s[7]*s[14] + s[4] *s[2]*s[15]
            - s[4]*s[3]*s[14] - s[12]*s[2]*s[7]  + s[12]*s[3]*s[6];
  inv[10] =   s[0]*s[5]*s[15] - s[0] *s[7]*s[13] - s[4] *s[1]*s[15]
            + s[4]*s[3]*s[13] + s[12]*s[1]*s[7]  - s[12]*s[3]*s[5];
  inv[14] = - s[0]*s[5]*s[14] + s[0] *s[6]*s[13] + s[4] *s[1]*s[14]
            - s[4]*s[2]*s[13] - s[12]*s[1]*s[6]  + s[12]*s[2]*s[5];

  inv[3]  = - s[1]*s[6]*s[11] + s[1]*s[7]*s[10] + s[5]*s[2]*s[11]
            - s[5]*s[3]*s[10] - s[9]*s[2]*s[7]  + s[9]*s[3]*s[6];
  inv[7]  =   s[0]*s[6]*s[11] - s[0]*s[7]*s[10] - s[4]*s[2]*s[11]
            + s[4]*s[3]*s[10] + s[8]*s[2]*s[7]  - s[8]*s[3]*s[6];
  inv[11] = - s[0]*s[5]*s[11] + s[0]*s[7]*s[9]  + s[4]*s[1]*s[11]
            - s[4]*s[3]*s[9]  - s[8]*s[1]*s[7]  + s[8]*s[3]*s[5];
  inv[15] =   s[0]*s[5]*s[10] - s[0]*s[6]*s[9]  - s[4]*s[1]*s[10]
            + s[4]*s[2]*s[9]  + s[8]*s[1]*s[6]  - s[8]*s[2]*s[5];

  det = s[0]*inv[0] + s[1]*inv[4] + s[2]*inv[8] + s[3]*inv[12];
  if (det === 0) {
    return this;
  }

  det = 1 / det;
  for (i = 0; i < 16; i++) {
    d[i] = inv[i] * det;
  }

  return this;
};

/**
 * Calculate the inverse matrix of this, and set to this.
 * @return this
 */
Matrix4.prototype.invert = function() {
  return this.setInverseOf(this);
};

/**
 * Set the orthographic projection matrix.
 * @param left The coordinate of the left of clipping plane.
 * @param right The coordinate of the right of clipping plane.
 * @param bottom The coordinate of the bottom of clipping plane.
 * @param top The coordinate of the top top clipping plane.
 * @param near The distances to the nearer depth clipping plane. This value is minus if the plane is to be behind the viewer.
 * @param far The distances to the farther depth clipping plane. This value is minus if the plane is to be behind the viewer.
 * @return this
 */
Matrix4.prototype.setOrtho = function(left, right, bottom, top, near, far) {
  var e, rw, rh, rd;

  if (left === right || bottom === top || near === far) {
    throw 'null frustum';
  }

  rw = 1 / (right - left);
  rh = 1 / (top - bottom);
  rd = 1 / (far - near);

  e = this.elements;

  e[0]  = 2 * rw;
  e[1]  = 0;
  e[2]  = 0;
  e[3]  = 0;

  e[4]  = 0;
  e[5]  = 2 * rh;
  e[6]  = 0;
  e[7]  = 0;

  e[8]  = 0;
  e[9]  = 0;
  e[10] = -2 * rd;
  e[11] = 0;

  e[12] = -(right + left) * rw;
  e[13] = -(top + bottom) * rh;
  e[14] = -(far + near) * rd;
  e[15] = 1;

  return this;
};

/**
 * Multiply the orthographic projection matrix from the right.
 * @param left The coordinate of the left of clipping plane.
 * @param right The coordinate of the right of clipping plane.
 * @param bottom The coordinate of the bottom of clipping plane.
 * @param top The coordinate of the top top clipping plane.
 * @param near The distances to the nearer depth clipping plane. This value is minus if the plane is to be behind the viewer.
 * @param far The distances to the farther depth clipping plane. This value is minus if the plane is to be behind the viewer.
 * @return this
 */
Matrix4.prototype.ortho = function(left, right, bottom, top, near, far) {
  return this.concat(new Matrix4().setOrtho(left, right, bottom, top, near, far));
};

/**
 * Set the perspective projection matrix.
 * @param left The coordinate of the left of clipping plane.
 * @param right The coordinate of the right of clipping plane.
 * @param bottom The coordinate of the bottom of clipping plane.
 * @param top The coordinate of the top top clipping plane.
 * @param near The distances to the nearer depth clipping plane. This value must be plus value.
 * @param far The distances to the farther depth clipping plane. This value must be plus value.
 * @return this
 */
Matrix4.prototype.setFrustum = function(left, right, bottom, top, near, far) {
  var e, rw, rh, rd;

  if (left === right || top === bottom || near === far) {
    throw 'null frustum';
  }
  if (near <= 0) {
    throw 'near <= 0';
  }
  if (far <= 0) {
    throw 'far <= 0';
  }

  rw = 1 / (right - left);
  rh = 1 / (top - bottom);
  rd = 1 / (far - near);

  e = this.elements;

  e[ 0] = 2 * near * rw;
  e[ 1] = 0;
  e[ 2] = 0;
  e[ 3] = 0;

  e[ 4] = 0;
  e[ 5] = 2 * near * rh;
  e[ 6] = 0;
  e[ 7] = 0;

  e[ 8] = (right + left) * rw;
  e[ 9] = (top + bottom) * rh;
  e[10] = -(far + near) * rd;
  e[11] = -1;

  e[12] = 0;
  e[13] = 0;
  e[14] = -2 * near * far * rd;
  e[15] = 0;

  return this;
};

/**
 * Multiply the perspective projection matrix from the right.
 * @param left The coordinate of the left of clipping plane.
 * @param right The coordinate of the right of clipping plane.
 * @param bottom The coordinate of the bottom of clipping plane.
 * @param top The coordinate of the top top clipping plane.
 * @param near The distances to the nearer depth clipping plane. This value must be plus value.
 * @param far The distances to the farther depth clipping plane. This value must be plus value.
 * @return this
 */
Matrix4.prototype.frustum = function(left, right, bottom, top, near, far) {
  return this.concat(new Matrix4().setFrustum(left, right, bottom, top, near, far));
};

/**
 * Set the perspective projection matrix by fovy and aspect.
 * @param fovy The angle between the upper and lower sides of the frustum.
 * @param aspect The aspect ratio of the frustum. (width/height)
 * @param near The distances to the nearer depth clipping plane. This value must be plus value.
 * @param far The distances to the farther depth clipping plane. This value must be plus value.
 * @return this
 */
Matrix4.prototype.setPerspective = function(fovy, aspect, near, far) {
  var e, rd, s, ct;

  if (near === far || aspect === 0) {
    throw 'null frustum';
  }
  if (near <= 0) {
    throw 'near <= 0';
  }
  if (far <= 0) {
    throw 'far <= 0';
  }

  fovy = Math.PI * fovy / 180 / 2;
  s = Math.sin(fovy);
  if (s === 0) {
    throw 'null frustum';
  }

  rd = 1 / (far - near);
  ct = Math.cos(fovy) / s;

  e = this.elements;

  e[0]  = ct / aspect;
  e[1]  = 0;
  e[2]  = 0;
  e[3]  = 0;

  e[4]  = 0;
  e[5]  = ct;
  e[6]  = 0;
  e[7]  = 0;

  e[8]  = 0;
  e[9]  = 0;
  e[10] = -(far + near) * rd;
  e[11] = -1;

  e[12] = 0;
  e[13] = 0;
  e[14] = -2 * near * far * rd;
  e[15] = 0;

  return this;
};

/**
 * Multiply the perspective projection matrix from the right.
 * @param fovy The angle between the upper and lower sides of the frustum.
 * @param aspect The aspect ratio of the frustum. (width/height)
 * @param near The distances to the nearer depth clipping plane. This value must be plus value.
 * @param far The distances to the farther depth clipping plane. This value must be plus value.
 * @return this
 */
Matrix4.prototype.perspective = function(fovy, aspect, near, far) {
  return this.concat(new Matrix4().setPerspective(fovy, aspect, near, far));
};

/**
 * Set the matrix for scaling.
 * @param x The scale factor along the X axis
 * @param y The scale factor along the Y axis
 * @param z The scale factor along the Z axis
 * @return this
 */
Matrix4.prototype.setScale = function(x, y, z) {
  var e = this.elements;
  e[0] = x;  e[4] = 0;  e[8]  = 0;  e[12] = 0;
  e[1] = 0;  e[5] = y;  e[9]  = 0;  e[13] = 0;
  e[2] = 0;  e[6] = 0;  e[10] = z;  e[14] = 0;
  e[3] = 0;  e[7] = 0;  e[11] = 0;  e[15] = 1;
  return this;
};

/**
 * Multiply the matrix for scaling from the right.
 * @param x The scale factor along the X axis
 * @param y The scale factor along the Y axis
 * @param z The scale factor along the Z axis
 * @return this
 */
Matrix4.prototype.scale = function(x, y, z) {
  var e = this.elements;
  e[0] *= x;  e[4] *= y;  e[8]  *= z;
  e[1] *= x;  e[5] *= y;  e[9]  *= z;
  e[2] *= x;  e[6] *= y;  e[10] *= z;
  e[3] *= x;  e[7] *= y;  e[11] *= z;
  return this;
};

/**
 * Set the matrix for translation.
 * @param x The X value of a translation.
 * @param y The Y value of a translation.
 * @param z The Z value of a translation.
 * @return this
 */
Matrix4.prototype.setTranslate = function(x, y, z) {
  var e = this.elements;
  e[0] = 1;  e[4] = 0;  e[8]  = 0;  e[12] = x;
  e[1] = 0;  e[5] = 1;  e[9]  = 0;  e[13] = y;
  e[2] = 0;  e[6] = 0;  e[10] = 1;  e[14] = z;
  e[3] = 0;  e[7] = 0;  e[11] = 0;  e[15] = 1;
  return this;
};

/**
 * Multiply the matrix for translation from the right.
 * @param x The X value of a translation.
 * @param y The Y value of a translation.
 * @param z The Z value of a translation.
 * @return this
 */
Matrix4.prototype.translate = function(x, y, z) {
  var e = this.elements;
  e[12] += e[0] * x + e[4] * y + e[8]  * z;
  e[13] += e[1] * x + e[5] * y + e[9]  * z;
  e[14] += e[2] * x + e[6] * y + e[10] * z;
  e[15] += e[3] * x + e[7] * y + e[11] * z;
  return this;
};

/**
 * Set the matrix for rotation.
 * The vector of rotation axis may not be normalized.
 * @param angle The angle of rotation (degrees)
 * @param x The X coordinate of vector of rotation axis.
 * @param y The Y coordinate of vector of rotation axis.
 * @param z The Z coordinate of vector of rotation axis.
 * @return this
 */
Matrix4.prototype.setRotate = function(angle, x, y, z) {
  var e, s, c, len, rlen, nc, xy, yz, zx, xs, ys, zs;

  angle = Math.PI * angle / 180;
  e = this.elements;

  s = Math.sin(angle);
  c = Math.cos(angle);

  if (0 !== x && 0 === y && 0 === z) {
    // Rotation around X axis
    if (x < 0) {
      s = -s;
    }
    e[0] = 1;  e[4] = 0;  e[ 8] = 0;  e[12] = 0;
    e[1] = 0;  e[5] = c;  e[ 9] =-s;  e[13] = 0;
    e[2] = 0;  e[6] = s;  e[10] = c;  e[14] = 0;
    e[3] = 0;  e[7] = 0;  e[11] = 0;  e[15] = 1;
  } else if (0 === x && 0 !== y && 0 === z) {
    // Rotation around Y axis
    if (y < 0) {
      s = -s;
    }
    e[0] = c;  e[4] = 0;  e[ 8] = s;  e[12] = 0;
    e[1] = 0;  e[5] = 1;  e[ 9] = 0;  e[13] = 0;
    e[2] =-s;  e[6] = 0;  e[10] = c;  e[14] = 0;
    e[3] = 0;  e[7] = 0;  e[11] = 0;  e[15] = 1;
  } else if (0 === x && 0 === y && 0 !== z) {
    // Rotation around Z axis
    if (z < 0) {
      s = -s;
    }
    e[0] = c;  e[4] =-s;  e[ 8] = 0;  e[12] = 0;
    e[1] = s;  e[5] = c;  e[ 9] = 0;  e[13] = 0;
    e[2] = 0;  e[6] = 0;  e[10] = 1;  e[14] = 0;
    e[3] = 0;  e[7] = 0;  e[11] = 0;  e[15] = 1;
  } else {
    // Rotation around another axis
    len = Math.sqrt(x*x + y*y + z*z);
    if (len !== 1) {
      rlen = 1 / len;
      x *= rlen;
      y *= rlen;
      z *= rlen;
    }
    nc = 1 - c;
    xy = x * y;
    yz = y * z;
    zx = z * x;
    xs = x * s;
    ys = y * s;
    zs = z * s;

    e[ 0] = x*x*nc +  c;
    e[ 1] = xy *nc + zs;
    e[ 2] = zx *nc - ys;
    e[ 3] = 0;

    e[ 4] = xy *nc - zs;
    e[ 5] = y*y*nc +  c;
    e[ 6] = yz *nc + xs;
    e[ 7] = 0;

    e[ 8] = zx *nc + ys;
    e[ 9] = yz *nc - xs;
    e[10] = z*z*nc +  c;
    e[11] = 0;

    e[12] = 0;
    e[13] = 0;
    e[14] = 0;
    e[15] = 1;
  }

  return this;
};

/**
 * Multiply the matrix for rotation from the right.
 * The vector of rotation axis may not be normalized.
 * @param angle The angle of rotation (degrees)
 * @param x The X coordinate of vector of rotation axis.
 * @param y The Y coordinate of vector of rotation axis.
 * @param z The Z coordinate of vector of rotation axis.
 * @return this
 */
Matrix4.prototype.rotate = function(angle, x, y, z) {
  return this.concat(new Matrix4().setRotate(angle, x, y, z));
};

/**
 * Set the viewing matrix.
 * @param eyeX, eyeY, eyeZ The position of the eye point.
 * @param centerX, centerY, centerZ The position of the reference point.
 * @param upX, upY, upZ The direction of the up vector.
 * @return this
 */
Matrix4.prototype.setLookAt = function(eyeX, eyeY, eyeZ, centerX, centerY, centerZ, upX, upY, upZ) {
  var e, fx, fy, fz, rlf, sx, sy, sz, rls, ux, uy, uz;

  fx = centerX - eyeX;
  fy = centerY - eyeY;
  fz = centerZ - eyeZ;

  // Normalize f.
  rlf = 1 / Math.sqrt(fx*fx + fy*fy + fz*fz);
  fx *= rlf;
  fy *= rlf;
  fz *= rlf;

  // Calculate cross product of f and up.
  sx = fy * upZ - fz * upY;
  sy = fz * upX - fx * upZ;
  sz = fx * upY - fy * upX;

  // Normalize s.
  rls = 1 / Math.sqrt(sx*sx + sy*sy + sz*sz);
  sx *= rls;
  sy *= rls;
  sz *= rls;

  // Calculate cross product of s and f.
  ux = sy * fz - sz * fy;
  uy = sz * fx - sx * fz;
  uz = sx * fy - sy * fx;

  // Set to this.
  e = this.elements;
  e[0] = sx;
  e[1] = ux;
  e[2] = -fx;
  e[3] = 0;

  e[4] = sy;
  e[5] = uy;
  e[6] = -fy;
  e[7] = 0;

  e[8] = sz;
  e[9] = uz;
  e[10] = -fz;
  e[11] = 0;

  e[12] = 0;
  e[13] = 0;
  e[14] = 0;
  e[15] = 1;

  // Translate.
  return this.translate(-eyeX, -eyeY, -eyeZ);
};

/**
 * Multiply the viewing matrix from the right.
 * @param eyeX, eyeY, eyeZ The position of the eye point.
 * @param centerX, centerY, centerZ The position of the reference point.
 * @param upX, upY, upZ The direction of the up vector.
 * @return this
 */
Matrix4.prototype.lookAt = function(eyeX, eyeY, eyeZ, centerX, centerY, centerZ, upX, upY, upZ) {
  return this.concat(new Matrix4().setLookAt(eyeX, eyeY, eyeZ, centerX, centerY, centerZ, upX, upY, upZ));
};

/**
 * Multiply the matrix for project vertex to plane from the right.
 * @param plane The array[A, B, C, D] of the equation of plane "Ax + By + Cz + D = 0".
 * @param light The array which stored coordinates of the light. if light[3]=0, treated as parallel light.
 * @return this
 */
Matrix4.prototype.dropShadow = function(plane, light) {
  var mat = new Matrix4();
  var e = mat.elements;

  var dot = plane[0] * light[0] + plane[1] * light[1] + plane[2] * light[2] + plane[3] * light[3];

  e[ 0] = dot - light[0] * plane[0];
  e[ 1] =     - light[1] * plane[0];
  e[ 2] =     - light[2] * plane[0];
  e[ 3] =     - light[3] * plane[0];

  e[ 4] =     - light[0] * plane[1];
  e[ 5] = dot - light[1] * plane[1];
  e[ 6] =     - light[2] * plane[1];
  e[ 7] =     - light[3] * plane[1];

  e[ 8] =     - light[0] * plane[2];
  e[ 9] =     - light[1] * plane[2];
  e[10] = dot - light[2] * plane[2];
  e[11] =     - light[3] * plane[2];

  e[12] =     - light[0] * plane[3];
  e[13] =     - light[1] * plane[3];
  e[14] =     - light[2] * plane[3];
  e[15] = dot - light[3] * plane[3];

  return this.concat(mat);
}

/**
 * Multiply the matrix for project vertex to plane from the right.(Projected by parallel light.)
 * @param normX, normY, normZ The normal vector of the plane.(Not necessary to be normalized.)
 * @param planeX, planeY, planeZ The coordinate of arbitrary points on a plane.
 * @param lightX, lightY, lightZ The vector of the direction of light.(Not necessary to be normalized.)
 * @return this
 */
Matrix4.prototype.dropShadowDirectionally = function(normX, normY, normZ, planeX, planeY, planeZ, lightX, lightY, lightZ) {
  var a = planeX * normX + planeY * normY + planeZ * normZ;
  return this.dropShadow([normX, normY, normZ, -a], [lightX, lightY, lightZ, 0]);
};

/**
 * Constructor of Vector3
 * If opt_src is specified, new vector is initialized by opt_src.
 * @param opt_src source vector(option)
 */
var Vector3 = function(opt_src) {
  var v = new Float32Array(3);
  if (opt_src && typeof opt_src === 'object') {
    v[0] = opt_src[0]; v[1] = opt_src[1]; v[2] = opt_src[2];
  } 
  this.elements = v;
}

/**
  * Normalize.
  * @return this
  */
Vector3.prototype.normalize = function() {
  var v = this.elements;
  var c = v[0], d = v[1], e = v[2], g = Math.sqrt(c*c+d*d+e*e);
  if(g){
    if(g == 1)
        return this;
   } else {
     v[0] = 0; v[1] = 0; v[2] = 0;
     return this;
   }
   g = 1/g;
   v[0] = c*g; v[1] = d*g; v[2] = e*g;
   return this;
};

/**
 * Constructor of Vector4
 * If opt_src is specified, new vector is initialized by opt_src.
 * @param opt_src source vector(option)
 */
var Vector4 = function(opt_src) {
  var v = new Float32Array(4);
  if (opt_src && typeof opt_src === 'object') {
    v[0] = opt_src[0]; v[1] = opt_src[1]; v[2] = opt_src[2]; v[3] = opt_src[3];
  } 
  this.elements = v;
}

// cuon-utils.js (c) 2012 kanda and matsuda
/**
 * Create a program object and make current
 * @param gl GL context
 * @param vshader a vertex shader program (string)
 * @param fshader a fragment shader program (string)
 * @return true, if the program object was created and successfully made current 
 */
function initShaders(gl, vshader, fshader) {
  var program = createProgram(gl, vshader, fshader);
  if (!program) {
    console.log('Failed to create program');
    return false;
  }

  gl.useProgram(program);
  gl.program = program;

  return true;
}

/**
 * Create the linked program object
 * @param gl GL context
 * @param vshader a vertex shader program (string)
 * @param fshader a fragment shader program (string)
 * @return created program object, or null if the creation has failed
 */
function createProgram(gl, vshader, fshader) {
  // Create shader object
  var vertexShader = loadShader(gl, gl.VERTEX_SHADER, vshader);
  var fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fshader);
  if (!vertexShader || !fragmentShader) {
    return null;
  }

  // Create a program object
  var program = gl.createProgram();
  if (!program) {
    return null;
  }

  // Attach the shader objects
  gl.attachShader(program, vertexShader);
  gl.attachShader(program, fragmentShader);

  // Link the program object
  gl.linkProgram(program);

  // Check the result of linking
  var linked = gl.getProgramParameter(program, gl.LINK_STATUS);
  if (!linked) {
    var error = gl.getProgramInfoLog(program);
    console.log('Failed to link program: ' + error);
    gl.deleteProgram(program);
    gl.deleteShader(fragmentShader);
    gl.deleteShader(vertexShader);
    return null;
  }
  return program;
}

/**
 * Create a shader object
 * @param gl GL context
 * @param type the type of the shader object to be created
 * @param source shader program (string)
 * @return created shader object, or null if the creation has failed.
 */
function loadShader(gl, type, source) {
  // Create shader object
  var shader = gl.createShader(type);
  if (shader == null) {
    console.log('unable to create shader');
    return null;
  }

  // Set the shader program
  gl.shaderSource(shader, source);

  // Compile the shader
  gl.compileShader(shader);

  // Check the result of compilation
  var compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
  if (!compiled) {
    var error = gl.getShaderInfoLog(shader);
    console.log('Failed to compile shader: ' + error);
    gl.deleteShader(shader);
    return null;
  }

  return shader;
}

/** 
 * Initialize and get the rendering for WebGL
 * @param canvas <cavnas> element
 * @param opt_debug flag to initialize the context for debugging
 * @return the rendering context for WebGL
 */
function getWebGLContext(canvas, opt_debug) {
  // Get the rendering context for WebGL
  var gl = WebGLUtils.setupWebGL(canvas);
  if (!gl) return null;

  // if opt_debug is explicitly false, create the context for debugging
  if (arguments.length < 2 || opt_debug) {
    gl = WebGLDebugUtils.makeDebugContext(gl);
  }

  return gl;
}

//从这里开始


let canvas  = document.getElementById("webgl");
let gl = canvas.getContext("webgl");
let VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
  'attribute vec4 a_Color;\n' +
  'attribute vec4 a_Normal;\n' +
  'uniform mat4 u_MvpMatrix;\n' +
  'uniform mat4 u_NormalMatrix;\n' +   // Transformation matrix of the normal
  'uniform vec3 u_LightColor;\n' +     // Light color
  'uniform vec3 u_LightDirection;\n' + // Light direction (in the world coordinate, normalized)
  'uniform vec3 u_AmbientLight;\n' +   // Ambient light color
  'varying vec4 v_Color;\n' +
  'void main() {\n' +
  '  gl_Position = u_MvpMatrix * a_Position;\n' +
     // Recalculate the normal based on the model matrix and make its length 1.
  '  vec3 normal = normalize(vec3(u_NormalMatrix * a_Normal));\n' +
     // Calculate the dot product of the light direction and the orientation of a surface (the normal)
  '  float nDotL = max(dot(u_LightDirection, normal), 0.0);\n' +
     // Calculate the color due to diffuse reflection
  '  vec3 diffuse = u_LightColor * a_Color.rgb * nDotL;\n' +
     // Calculate the color due to ambient reflection
  '  vec3 ambient = u_AmbientLight * a_Color.rgb;\n' +
     // Add the surface colors due to diffuse reflection and ambient reflection
  '  v_Color = vec4(diffuse + ambient, a_Color.a);\n' + 
  '}\n';

let FSHADER_SOURCE = 
'precision mediump float;' + 
'varying vec4 v_Color;' +
'void main() {' +
	' gl_FragColor = v_Color;' +
'}';

initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE);

let n = initVertexBuffers(gl);

gl.enable(gl.DEPTH_TEST);
gl.clearColor(0.0, 0.0, 0.0, 1.0);

let u_MvpMatrix = gl.getUniformLocation(gl.program, 'u_MvpMatrix');
let u_LightColor = gl.getUniformLocation(gl.program, 'u_LightColor');
let u_LightDirection = gl.getUniformLocation(gl.program, 'u_LightDirection');
let u_AmbientLight = gl.getUniformLocation(gl.program, 'u_AmbientLight');
let u_NormalMatrix = gl.getUniformLocation(gl.program, 'u_NormalMatrix');

// Set the light color (white)
gl.uniform3f(u_LightColor, 1.0, 1.0, 1.0);

let lightDirection = new Vector3([0.5, 3.0, 4.0]);
lightDirection.normalize();     // Normalize
gl.uniform3fv(u_LightDirection, lightDirection.elements);
// Set the ambient light
gl.uniform3f(u_AmbientLight, 0.2, 0.2, 0.2);

let mvpMatrix = new Matrix4();
let modelMatrix = new Matrix4();  // Model matrix
let normalMatrix = new Matrix4(); // Transformation matrix for normals
// Set the eye point, look-at point, and up vector.
mvpMatrix.setPerspective(30, 1, 1, 100);
mvpMatrix.lookAt(3, 3, 7, 0, 0, 0, 0, 1, 0);

// Calculate the model matrix
modelMatrix.setTranslate(0, 0.9, 0); // Translate to the y-axis direction
modelMatrix.rotate(30, 0, 0, 1);     // Rotate 90 degree around the z-axis
// Calculate the view projection matrix
mvpMatrix.setPerspective(30, canvas.width/canvas.height, 1, 100);
mvpMatrix.lookAt(3, 3, 7, 0, 0, 0, 0, 1, 0);
mvpMatrix.multiply(modelMatrix);
// Pass the model view projection matrix to u_MvpMatrix
gl.uniformMatrix4fv(u_MvpMatrix, false, mvpMatrix.elements);

// Calculate the matrix to transform the normal based on the model matrix
normalMatrix.setInverseOf(modelMatrix);
normalMatrix.transpose();
// Pass the transformation matrix for normals to u_NormalMatrix
gl.uniformMatrix4fv(u_NormalMatrix, false, normalMatrix.elements);

// Clear color and depth buffer
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

// Draw the cube
gl.drawElements(gl.TRIANGLES, n, gl.UNSIGNED_BYTE, 0);
  

function initVertexBuffers(gl) {
  // Create a cube
  //    v6----- v5
  //   /|      /|
  //  v1------v0|
  //  | |     | |
  //  | |v7---|-|v4
  //  |/      |/
  //  v2------v3

  let vertices = new Float32Array([   // Coordinates
     1.0, 1.0, 1.0,  -1.0, 1.0, 1.0,  -1.0,-1.0, 1.0,   1.0,-1.0, 1.0, // v0-v1-v2-v3 front
     1.0, 1.0, 1.0,   1.0,-1.0, 1.0,   1.0,-1.0,-1.0,   1.0, 1.0,-1.0, // v0-v3-v4-v5 right
     1.0, 1.0, 1.0,   1.0, 1.0,-1.0,  -1.0, 1.0,-1.0,  -1.0, 1.0, 1.0, // v0-v5-v6-v1 up
    -1.0, 1.0, 1.0,  -1.0, 1.0,-1.0,  -1.0,-1.0,-1.0,  -1.0,-1.0, 1.0, // v1-v6-v7-v2 left
    -1.0,-1.0,-1.0,   1.0,-1.0,-1.0,   1.0,-1.0, 1.0,  -1.0,-1.0, 1.0, // v7-v4-v3-v2 down
     1.0,-1.0,-1.0,  -1.0,-1.0,-1.0,  -1.0, 1.0,-1.0,   1.0, 1.0,-1.0  // v4-v7-v6-v5 back
  ]);

  let colors = new Float32Array([    // Colors
    1, 0, 0,   1, 0, 0,   1, 0, 0,  1, 0, 0,     // v0-v1-v2-v3 front
    1, 0, 0,   1, 0, 0,   1, 0, 0,  1, 0, 0,     // v0-v3-v4-v5 right
    1, 0, 0,   1, 0, 0,   1, 0, 0,  1, 0, 0,     // v0-v5-v6-v1 up
    1, 0, 0,   1, 0, 0,   1, 0, 0,  1, 0, 0,     // v1-v6-v7-v2 left
    1, 0, 0,   1, 0, 0,   1, 0, 0,  1, 0, 0,     // v7-v4-v3-v2 down
    1, 0, 0,   1, 0, 0,   1, 0, 0,  1, 0, 0     // v4-v7-v6-v5 back
 ]);


  let normals = new Float32Array([    // Normal
    0.0, 0.0, 1.0,   0.0, 0.0, 1.0,   0.0, 0.0, 1.0,   0.0, 0.0, 1.0,  // v0-v1-v2-v3 front
    1.0, 0.0, 0.0,   1.0, 0.0, 0.0,   1.0, 0.0, 0.0,   1.0, 0.0, 0.0,  // v0-v3-v4-v5 right
    0.0, 1.0, 0.0,   0.0, 1.0, 0.0,   0.0, 1.0, 0.0,   0.0, 1.0, 0.0,  // v0-v5-v6-v1 up
   -1.0, 0.0, 0.0,  -1.0, 0.0, 0.0,  -1.0, 0.0, 0.0,  -1.0, 0.0, 0.0,  // v1-v6-v7-v2 left
    0.0,-1.0, 0.0,   0.0,-1.0, 0.0,   0.0,-1.0, 0.0,   0.0,-1.0, 0.0,  // v7-v4-v3-v2 down
    0.0, 0.0,-1.0,   0.0, 0.0,-1.0,   0.0, 0.0,-1.0,   0.0, 0.0,-1.0   // v4-v7-v6-v5 back
  ]);
  
  // Indices of the vertices
  let indices = new Uint8Array([
     0, 1, 2,   0, 2, 3,    // front
     4, 5, 6,   4, 6, 7,    // right
     8, 9,10,   8,10,11,    // up
    12,13,14,  12,14,15,    // left
    16,17,18,  16,18,19,    // down
    20,21,22,  20,22,23     // back
 ]);

 // Write the vertex property to buffers (coordinates, colors and normals)
  if (!initArrayBuffer(gl, 'a_Position', vertices, 3, gl.FLOAT)) return -1;
  if (!initArrayBuffer(gl, 'a_Color', colors, 3, gl.FLOAT)) return -1;
  if (!initArrayBuffer(gl, 'a_Normal', normals, 3, gl.FLOAT)) return -1;
  
  // Create a buffer object
  var indexBuffer = gl.createBuffer();
  
  // Write the indices to the buffer object
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

  return indices.length;
}

function initArrayBuffer (gl, attribute, data, num, type) {
  // Create a buffer object
  var buffer = gl.createBuffer();
  if (!buffer) {
    console.log('Failed to create the buffer object');
    return false;
  }
  // Write date into the buffer object
  gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
  gl.bufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW);
  // Assign the buffer object to the attribute variable
  var a_attribute = gl.getAttribLocation(gl.program, attribute);
  if (a_attribute < 0) {
    console.log('Failed to get the storage location of ' + attribute);
    return false;
  }
  gl.vertexAttribPointer(a_attribute, num, type, false, 0, 0);
  // Enable the assignment of the buffer object to the attribute variable
  gl.enableVertexAttribArray(a_attribute);

  gl.bindBuffer(gl.ARRAY_BUFFER, null);

  return true;
}

              
<canvas id="webgl" width="400" height="400"></canvas>