Detailed introduction on how to implement HTML5 3D clothes swing animation special effects

<p style="width:500px;margin:10px auto">
	<canvas id="cv" width="480" height="300"></canvas>
	<p>"3D on 2D Canvas" demo</p>
	<p>move cursor to pan / click to swing</p>
</p>

window.P3D = {
	texture: null,
	g: null
};

P3D.clear = function(f, w, h) {
	var g = this.g;
	g.beginPath();
	g.fillStyle = f;
	g.fillRect(0, 0, w, h);

}

P3D.num_cmp = function(a,b){return a-b;}

P3D.drawTriangle = function(poss, uvs, shade_clr) {
	var w = this.texture.width;
	var h = this.texture.height;

	var g = this.g;

	var vAd = [ poss[1].x - poss[0].x , poss[1].y - poss[0].y ];
	var vBd = [ poss[2].x - poss[0].x , poss[2].y - poss[0].y ];

	var vA = [ uvs[1].u - uvs[0].u , uvs[1].v - uvs[0].v ];
	var vB = [ uvs[2].u - uvs[0].u , uvs[2].v - uvs[0].v ];

	vA[0] *= w;
	vA[1] *= h;

	vB[0] *= w;
	vB[1] *= h;

	var m = new M22();
	m._11 = vA[0];
	m._12 = vA[1];
	m._21 = vB[0];
	m._22 = vB[1];

	var im = m.getInvert();
	if (!im) return false;

	var a = im._11 * vAd[0] + im._12 * vBd[0];
	var b = im._21 * vAd[0] + im._22 * vBd[0];

	var c = im._11 * vAd[1] + im._12 * vBd[1];
	var d = im._21 * vAd[1] + im._22 * vBd[1];

	var wu = uvs[0].u * w;
	var hv = uvs[0].v * h;
	var du = wu * a + hv * b;
	var dv = wu * c + hv * d;

	g.save();

	g.beginPath();
	g.moveTo(poss[0].x, poss[0].y);
	g.lineTo(poss[1].x, poss[1].y);
	g.lineTo(poss[2].x, poss[2].y);
	g.clip();

	g.transform(a, c, b, d, poss[0].x - du, poss[0].y - dv);

	// bounds
	var bx = [wu, wu+vA[0], wu+vB[0]];
	var by = [hv, hv+vA[1], hv+vB[1]];

	bx.sort(P3D.num_cmp);
	by.sort(P3D.num_cmp);

	var bw = bx[2] - bx[0];
	var bh = by[2] - by[0];

	if ((bx[0]+bw) <= (w-1)) bw++;
	if ((by[0]+bh) <= (h-1)) bh++;
	if (bx[0] >= 1) {bx[0]--; bw++;}
	if (by[0] >= 1) {by[0]--; bh++;}

	g.drawImage(this.texture, bx[0], by[0], bw, bh, bx[0], by[0], bw, bh);

	if (shade_clr) {
		g.fillStyle = shade_clr;
		g.fillRect(bx[0], by[0], bw, bh);
	}

	g.restore();

	return true;
}

P3D.drawTestByIndexBuffer = function(pos_buf, ix_buf, culling) {
	var g = this.g;

	if ((ix_buf.length%3) != 0)
		throw "invalid index buffer length!";

	var len = ix_buf.length/3;

	var i, ibase, vbase;
	var poss = [{},{},{}];
	g.strokeWidth = 1;
	for (i = 0, ibase = 0;i < len;++i)
	{
		vbase = ix_buf[ibase++] << 2;
		poss[0].x = pos_buf[vbase++];
		poss[0].y = pos_buf[vbase  ];

		vbase = ix_buf[ibase++] << 2;
		poss[1].x = pos_buf[vbase++];
		poss[1].y = pos_buf[vbase  ];

		vbase = ix_buf[ibase++] << 2;
		poss[2].x = pos_buf[vbase++];
		poss[2].y = pos_buf[vbase  ];

		// z component of cross product < 0 ?

		var Ax = poss[1].x - poss[0].x;
		var Ay = poss[1].y - poss[0].y;
		var Cx = poss[2].x - poss[1].x;
		var Cy = poss[2].y - poss[1].y;

		var cull = ( (((Ax * Cy) - (Ay * Cx))*culling) < 0);

		g.beginPath();
		g.strokeStyle = cull ? "#592" : "#0f0";
		g.moveTo(poss[0].x, poss[0].y);
		g.lineTo(poss[1].x, poss[1].y);
		g.lineTo(poss[2].x, poss[2].y);
		g.lineTo(poss[0].x, poss[0].y);
		g.stroke();
	}
}

P3D.drawByIndexBuffer = function(pos_buf, ix_buf, tx_buf, culling, z_clip) {
	var w, h;
	var color_polygon = !this.texture;
	if (this.texture) {
		w = this.texture.width;
		h = this.texture.height;
	}

	var g = this.g;
	var m = new M22();

	if (!culling) culling = 0;

	if ((ix_buf.length%3) != 0)
		throw "invalid index buffer length!";

	var i, ibase, vbase, tbase, poss = [{},{},{}];
	var len = ix_buf.length/3;
	var uv_0u, uv_0v, uv_1u, uv_1v, uv_2u, uv_2v;

	for (i = 0, ibase = 0;i < len;++i)
	{
		tbase = ix_buf[ibase++] << 1
		vbase = tbase << 1;
		poss[0].x = pos_buf[vbase++]; uv_0u = tx_buf[tbase++];
		poss[0].y = pos_buf[vbase++]; uv_0v = tx_buf[tbase];
		if (z_clip && (pos_buf[vbase] < 0 || pos_buf[vbase] > 1)) {ibase += 2; continue;}

		tbase = ix_buf[ibase++] << 1
		vbase = tbase << 1;
		poss[1].x = pos_buf[vbase++]; uv_1u = tx_buf[tbase++];
		poss[1].y = pos_buf[vbase++]; uv_1v = tx_buf[tbase];
		if (z_clip && (pos_buf[vbase] < 0 || pos_buf[vbase] > 1)) {++ibase; continue;}

		tbase = ix_buf[ibase++] << 1
		vbase = tbase << 1;
		poss[2].x = pos_buf[vbase++]; uv_2u = tx_buf[tbase++];
		poss[2].y = pos_buf[vbase++]; uv_2v = tx_buf[tbase];
		if (z_clip && (pos_buf[vbase] < 0 || pos_buf[vbase] > 1)) {continue;}

		var vAd = [ poss[1].x - poss[0].x , poss[1].y - poss[0].y ];
		var vBd = [ poss[2].x - poss[0].x , poss[2].y - poss[0].y ];

		var vCd = [ poss[2].x - poss[1].x , poss[2].y - poss[1].y ];

		// z component of cross product < 0 ?
		if( (((vAd[0] * vCd[1]) - (vAd[1] * vCd[0]))*culling) < 0)
			continue;

		if (color_polygon) {
			g.fillStyle = uv_0u;

			g.beginPath();
			g.moveTo(poss[0].x, poss[0].y);
			g.lineTo(poss[1].x, poss[1].y);
			g.lineTo(poss[2].x, poss[2].y);
			g.fill();
			continue;
		}

		var vA = [ uv_1u - uv_0u , uv_1v - uv_0v ];
		var vB = [ uv_2u - uv_0u , uv_2v - uv_0v ];

		vA[0] *= w;
		vA[1] *= h;

		vB[0] *= w;
		vB[1] *= h;

		m._11 = vA[0];
		m._12 = vA[1];
		m._21 = vB[0];
		m._22 = vB[1];

		var im = m.getInvert();
		if (!im) { continue;}

		var a = im._11 * vAd[0] + im._12 * vBd[0];
		var b = im._21 * vAd[0] + im._22 * vBd[0];

		var c = im._11 * vAd[1] + im._12 * vBd[1];
		var d = im._21 * vAd[1] + im._22 * vBd[1];

		var wu = uv_0u * w;
		var hv = uv_0v * h;
		var du = wu * a + hv * b;
		var dv = wu * c + hv * d;

		g.save();

		g.beginPath();
		g.moveTo(poss[0].x, poss[0].y);
		g.lineTo(poss[1].x, poss[1].y);
		g.lineTo(poss[2].x, poss[2].y);
		g.clip();
		g.transform(a, c, b, d, poss[0].x - du, poss[0].y - dv);

		// bounds
		var bx = [wu, wu+vA[0], wu+vB[0]];
		var by = [hv, hv+vA[1], hv+vB[1]];

		bx.sort(P3D.num_cmp);
		by.sort(P3D.num_cmp);

		var bw = bx[2] - bx[0];
		var bh = by[2] - by[0];

		if ((bx[0]+bw) <= (w-1)) bw++;
		if ((by[0]+bh) <= (h-1)) bh++;
		if (bx[0] >= 1) {bx[0]--; bw++;}
		if (by[0] >= 1) {by[0]--; bh++;}

		g.drawImage(this.texture, bx[0], by[0], bw, bh, bx[0], by[0], bw, bh);
/*
		if (shade_clr) {
			g.fillStyle = shade_clr;
			g.fillRect(bx[0], by[0], bw, bh);
		}
*/
		g.restore();

	}

}

function Vec3(_x, _y, _z)
{
	this.x = _x || 0;
	this.y = _y || 0;
	this.z = _z || 0;
}

Vec3.prototype = {
	zero: function() {
		this.x = this.y = this.z = 0;
	},

	sub: function(v) {
		this.x -= v.x;
		this.y -= v.y;
		this.z -= v.z;

		return this;
	},

	add: function(v) {
		this.x += v.x;
		this.y += v.y;
		this.z += v.z;

		return this;
	},

	copyFrom: function(v) {
		this.x = v.x;
		this.y = v.y;
		this.z = v.z;

		return this;
	},

	norm:function() {
		return Math.sqrt(this.x*this.x + this.y*this.y + this.z*this.z);
	},

	normalize: function() {
		var nrm = Math.sqrt(this.x*this.x + this.y*this.y + this.z*this.z);
		if (nrm != 0)
		{
			this.x /= nrm;
			this.y /= nrm;
			this.z /= nrm;
		}
		return this;
	},

	smul: function(k) {
		this.x *= k;
		this.y *= k;
		this.z *= k;

		return this;
	},

	dpWith: function(v)	{
		return this.x*v.x + this.y*v.y + this.z*v.z;
	},

	cp: function(v, w) {
		this.x = (w.y * v.z) - (w.z * v.y);
		this.y = (w.z * v.x) - (w.x * v.z);
		this.z = (w.x * v.y) - (w.y * v.x);

		return this;
	},

	toString: function() {
		return this.x + ", " + this.y + "," + this.z;
	}
}

function M44(cpy)
{
	if (cpy)
		this.copyFrom(cpy);
	else {
		this.ident();
	}
}

M44.prototype = {
	ident: function() {
			  this._12 = this._13 = this._14 = 0;
		this._21 =       this._23 = this._24 = 0;
		this._31 = this._32 =       this._34 = 0;
		this._41 = this._42 = this._43 =       0;

		this._11 = this._22 = this._33 = this._44 = 1;

		return this;
	},

	copyFrom: function(m) {
		this._11 = m._11;
		this._12 = m._12;
		this._13 = m._13;
		this._14 = m._14;

		this._21 = m._21;
		this._22 = m._22;
		this._23 = m._23;
		this._24 = m._24;

		this._31 = m._31;
		this._32 = m._32;
		this._33 = m._33;
		this._34 = m._34;

		this._41 = m._41;
		this._42 = m._42;
		this._43 = m._43;
		this._44 = m._44;

		return this;
	},

	transVec3: function(out, x, y, z) {
		out[0] = x * this._11 + y * this._21 + z * this._31 + this._41;
		out[1] = x * this._12 + y * this._22 + z * this._32 + this._42;
		out[2] = x * this._13 + y * this._23 + z * this._33 + this._43;
		out[3] = x * this._14 + y * this._24 + z * this._34 + this._44;
	},

	transVec3Rot: function(out, x, y, z) {
		out[0] = x * this._11 + y * this._21 + z * this._31;
		out[1] = x * this._12 + y * this._22 + z * this._32;
		out[2] = x * this._13 + y * this._23 + z * this._33;
	},

	perspectiveLH: function(vw, vh, z_near, z_far) {
		this._11 = 2.0*z_near/vw;
		this._12 = 0;
		this._13 = 0;
		this._14 = 0;

		this._21 = 0;
		this._22 = 2*z_near/vh;
		this._23 = 0;
		this._24 = 0;

		this._31 = 0;
		this._32 = 0;
		this._33 = z_far/(z_far-z_near);
		this._34 = 1;

		this._41 = 0;
		this._42 = 0;
		this._43 = z_near*z_far/(z_near-z_far);
		this._44 = 0;

		return this;
	},

	lookAtLH: function(aUp, aFrom, aAt) {
		var aX = new Vec3();
		var aY = new Vec3();

		var aZ = new Vec3(aAt.x, aAt.y, aAt.z);
		aZ.sub(aFrom).normalize();

		aX.cp(aUp, aZ).normalize();
		aY.cp(aZ, aX);

		this._11 = aX.x;  this._12 = aY.x;  this._13 = aZ.x;  this._14 = 0;
		this._21 = aX.y;  this._22 = aY.y;  this._23 = aZ.y;  this._24 = 0;
		this._31 = aX.z;  this._32 = aY.z;  this._33 = aZ.z;  this._34 = 0;

		this._41 = -aFrom.dpWith(aX);
		this._42 = -aFrom.dpWith(aY);
		this._43 = -aFrom.dpWith(aZ);
		this._44 = 1;

	    return this;
	},

	mul: function(A, B) {
		this._11 = A._11*B._11  +  A._12*B._21  +  A._13*B._31  +  A._14*B._41;
		this._12 = A._11*B._12  +  A._12*B._22  +  A._13*B._32  +  A._14*B._42;
		this._13 = A._11*B._13  +  A._12*B._23  +  A._13*B._33  +  A._14*B._43;
		this._14 = A._11*B._14  +  A._12*B._24  +  A._13*B._34  +  A._14*B._44;

		this._21 = A._21*B._11  +  A._22*B._21  +  A._23*B._31  +  A._24*B._41;
		this._22 = A._21*B._12  +  A._22*B._22  +  A._23*B._32  +  A._24*B._42;
		this._23 = A._21*B._13  +  A._22*B._23  +  A._23*B._33  +  A._24*B._43;
		this._24 = A._21*B._14  +  A._22*B._24  +  A._23*B._34  +  A._24*B._44;

		this._31 = A._31*B._11  +  A._32*B._21  +  A._33*B._31  +  A._34*B._41;
		this._32 = A._31*B._12  +  A._32*B._22  +  A._33*B._32  +  A._34*B._42;
		this._33 = A._31*B._13  +  A._32*B._23  +  A._33*B._33  +  A._34*B._43;
		this._34 = A._31*B._14  +  A._32*B._24  +  A._33*B._34  +  A._34*B._44;

		this._41 = A._41*B._11  +  A._42*B._21  +  A._43*B._31  +  A._44*B._41;
		this._42 = A._41*B._12  +  A._42*B._22  +  A._43*B._32  +  A._44*B._42;
		this._43 = A._41*B._13  +  A._42*B._23  +  A._43*B._33  +  A._44*B._43;
		this._44 = A._41*B._14  +  A._42*B._24  +  A._43*B._34  +  A._44*B._44;

		return this;
	},

	translate: function(x, y, z) {
		this._11 = 1;  this._12 = 0;  this._13 = 0;  this._14 = 0;
		this._21 = 0;  this._22 = 1;  this._23 = 0;  this._24 = 0;
		this._31 = 0;  this._32 = 0;  this._33 = 1;  this._34 = 0;

		this._41 = x;  this._42 = y;  this._43 = z;  this._44 = 1;
		return this;
	},

	transpose33: function() {
		var t;

		t = this._12;
		this._12 = this._21;
		this._21 = t;

		t = this._13;
		this._13 = this._31;
		this._31 = t;

		t = this._23;
		this._23 = this._32;
		this._32 = t;

		return this;
	},

	// OpenGL style rotation
	glRotate: function(angle, x, y, z) {
		var s = Math.sin( angle );
		var c = Math.cos( angle );

		var xx = x * x;
		var yy = y * y;
		var zz = z * z;
		var xy = x * y;
		var yz = y * z;
		var zx = z * x;
		var xs = x * s;
		var ys = y * s;
		var zs = z * s;
		var one_c = 1.0 - c;
/*
		this._11 = (one_c * xx) + c;
		this._21 = (one_c * xy) - zs;
		this._31 = (one_c * zx) + ys;
		this._41 = 0;

		this._12 = (one_c * xy) + zs;
		this._22 = (one_c * yy) + c;
		this._32 = (one_c * yz) - xs;
		this._42 = 0;

		this._13 = (one_c * zx) - ys;
		this._23 = (one_c * yz) + xs;
		this._33 = (one_c * zz) + c;
		this._43 = 0;

		this._14 = 0;
		this._24 = 0;
		this._34 = 0;
		this._44 = 1;
*/

		this._11 = (one_c * xx) + c;
		this._12 = (one_c * xy) - zs;
		this._13 = (one_c * zx) + ys;
		this._14 = 0;

		this._21 = (one_c * xy) + zs;
		this._22 = (one_c * yy) + c;
		this._23 = (one_c * yz) - xs;
		this._24 = 0;

		this._31 = (one_c * zx) - ys;
		this._32 = (one_c * yz) + xs;
		this._33 = (one_c * zz) + c;
		this._34 = 0;

		this._41 = 0;
		this._42 = 0;
		this._43 = 0;
		this._44 = 1;

		return this;
	}

}

// matrix 2x2
function M22()
{
	this._11 = 1;
	this._12 = 0;
	this._21 = 0;
	this._22 = 1;
}

M22.prototype.getInvert = function()
{
	var out = new M22();
	var det = this._11 * this._22 - this._12 * this._21;
	if (det > -0.0001 && det < 0.0001)
		return null;

	out._11 = this._22 / det;
	out._22 = this._11 / det;

	out._12 = -this._12 / det;
	out._21 = -this._21 / det;

	return out;
}

function ClothApp()
{
	this.canvas = document.getElementById("cv");

	P3D.g = this.canvas.getContext("2d");

	var tex = new Image();
	this.texture1 = tex;
	tex.onload = function(){ _this.start(); };
	tex.src = "20090226032826.gif";

	tex = new Image();
	this.texture2 = tex;
	tex.onload = function(){ _this.start(); };
	tex.src = "20090226032825.png";

	this.mLoadCount = 2;
	this.mTickCount = 0;

	this.G = 0.53;
	this.G1 = 0.45;
	this.mProjMat  = null;
	this.mViewMat  = null;
	this.mViewFrom = new Vec3();
	this.mViewFrom.y = -150;
	this.mViewFrom.z = 1000;
	this.mViewFromA = (new Vec3()).copyFrom(this.mViewFrom);

	this.mViewAngle = 0;

	this.mNLen = 0;
	this.mNodes = [];
	this.mRenderTris = null;

	this.mLTNode = null;
	this.mRTNode = null;

	this.mLTNodeV = new Vec3();
	this.mRTNodeV = new Vec3();

	this.mWForce = new Vec3();
	this.frate = 15;

	var _this = this;
}

ClothApp.zsortCmp = function(t1, t2) {
	return t2.sortKey - t1.sortKey;
}

ClothApp.prototype = {
	start: function() {
		if (--this.mLoadCount != 0) return;

		this.vUP = new Vec3(0,  1, 0);
		this.vAT = new Vec3(0, 80, 0);

		this.mViewport = {};
		this.mViewport.w = 480;
		this.mViewport.h = 300;
		this.mViewport.ow = 240;
		this.mViewport.oh = 150;
		this.setupTransforms();

		this.generateCloth(180);
		this.generateRenderTriangles();

		var _this = this;
		this.canvas.addEventListener("mousemove", function(e){_this.onMouseMove(e);}, false);
		this.canvas.addEventListener("mousedown", function(e){_this.onClick(e);}, false);

		window.setTimeout(function(){_this.onInterval();}, this.frate);
	},

	onInterval: function() {
		this.mTickCount++;

		// this.mLTNodeV.z = Math.cos(this.mTickCount*0.1) * 2;

		this.tick();
		this.updatePosition();
		this.draw();

		var _this = this;
		window.setTimeout(function(){_this.onInterval();}, this.frate);
	},

	onMouseMove: function(e) {
		if (e.clientX || e.clientX == 0)
			this.mViewAngle = (e.clientX - 240) * 0.004;

		if (e.clientY || e.clientY == 0)
			this.mViewFromA.y = 90 - (e.clientY - 0) * 0.8;
	},

	onClick: function(e) {
		if (e.clientX || e.clientX == 0)
		{
			this.mWForce.z = -4;
			this.mWForce.x = (e.clientX - 240) * -0.03;
		}
	},

	tick: function() {
		this.updateViewTrans(this.mViewAngle);

		var nlen = this.mNodes.length;
		var i, nd;
		for(i = 0;i < nlen;i++)
		{
			nd = this.mNodes[i];
			nd.F.x = 0;
			nd.F.z = 0;
			if (nd.flags & 4)
				nd.F.y = -this.G1;
			else
				nd.F.y = -this.G;

			nd.F.add(this.mWForce);
		}

		this.mWForce.zero();
		this.applyTension();

		for(i = 0;i < nlen;i++)
		{
			nd = this.mNodes[i];

			if ((nd.flags&1) != 0) {
				nd.F.sub(nd.F);
			}

			nd.velo.add(nd.F);
		}

		this.mLTNode.velo.copyFrom(this.mLTNodeV);
		this.mRTNode.velo.copyFrom(this.mRTNodeV);
	},

	updatePosition: function() {
		var nlen = this.mNodes.length;
		var i, nd;
		for(i = 0;i < nlen;i++)
		{
			nd = this.mNodes[i];

			if ((nd.flags&1) != 0) {
				nd.cv.x = 0;
				nd.cv.y = 0;
				nd.cv.z = 0;
			}

			nd.pos.add(nd.velo);
			nd.velo.sub(nd.cv);
			nd.cv.x = 0;
			nd.cv.y = 0;
			nd.cv.z = 0;

			nd.velo.smul(0.95);
		}
	},

	draw: function() {
		P3D.clear("#000", this.mViewport.w, this.mViewport.h);
		this.transformPolygons();

		this.mRenderTris.sort(ClothApp.zsortCmp);
		var len = this.mRenderTris.length;
		var t, sh;
		for (var i = 0;i < len;i++) {
			t = this.mRenderTris[i];

			if (P3D.texture != t.texture)
				P3D.texture = t.texture;

			sh = undefined;
			if (t.lighting && t.shade > 0.01)
				sh = "rgba(0,0,0,"+t.shade+")";
			P3D.drawTriangle(t.tposs, t.uvs, sh);
		}
	},

	applyTension: function() {
		var i, k, nd;
		var v = new Vec3();
		var nlen = this.mNodes.length;
		var naturalLen = this.mNLen;

		for (k = 0;k < nlen;k++)
		{
			nd = this.mNodes[k];
			var F = nd.F;

			for (i = 0;i < 4;i++)
			{
				var nbr = nd.links[i];
				if (!nbr) continue;

				var len = v.copyFrom(nbr.pos).sub(nd.pos).norm();
				var dlen = len - naturalLen;
				if (dlen > 0) {
					v.smul(dlen * 0.5 / len);

					F.x += v.x;
					F.y += v.y;
					F.z += v.z;
					nd.cv.add(v.smul(0.8));
				}
			}
		}	
	},

	setupTransforms: function() {
		this.mProjMat = new M44();
		this.mProjMat.perspectiveLH(24, 15, 10, 9000);

		this.mViewMat = new M44();
		this.updateViewTrans(0);
	},

	updateViewTrans: function(ry) {
		this.mViewFromA.z = Math.cos(ry) * 380;
		this.mViewFromA.x = Math.sin(ry) * 380;

		this.mViewFrom.smul(0.7);
		this.mViewFrom.x += this.mViewFromA.x * 0.3;
		this.mViewFrom.y += this.mViewFromA.y * 0.3;
		this.mViewFrom.z += this.mViewFromA.z * 0.3;

		this.mViewMat.lookAtLH(this.vUP, this.mViewFrom, this.vAT);
	},

	generateCloth: function(base_y) {
		var cols = 9;
		var rows = 8;

		var step   = 22;
		this.mNLen = step*0.9;
		var w = (cols-1) * step;

		var i, k;
		for (k = 0;k < rows;k++)
		{
			for (i = 0;i < cols;i++)
			{
				var nd = new ClothNode();
				nd.pos.x = -(w/2) + i*step;
				nd.pos.y = base_y -k*step/2;
				nd.pos.z = k*16;

				nd.uv.u = i / (cols-1);
				nd.uv.v = k / (rows-1);

				if (i > 0) {
					var prv_nd = this.mNodes[this.mNodes.length-1];
					prv_nd.links[1] = nd;
					nd.links[0] = prv_nd;
				}

				if (k > 0) {
					var up_nd = this.mNodes[this.mNodes.length-cols];
					up_nd.links[4] = nd;
					nd.links[3] = up_nd;
				}

				if (i != 0 && i != 4 && i != (cols-1))
					nd.flags |= 4;

				this.mNodes.push(nd);
			}
		}

		// fix left-top and right-top
		this.mNodes[0     ].flags |= 1;
		this.mNodes[4     ].flags |= 1;
		this.mNodes[cols-1].flags |= 1;

		this.mLTNode = this.mNodes[0     ];
		this.mRTNode = this.mNodes[cols-1];
	},

	generateRenderTriangles: function()
	{
		if (!this.mRenderTris) this.mRenderTris = [];

		var i;
		var nd;
		var nlen = this.mNodes.length;

		for(i = 0;i < nlen;i++)
		{
			nd = this.mNodes[i];
			if (nd.links[1] && nd.links[1].links[4]) {
				var t = new RenderTriangle();
				t.texture = this.texture1;

				t.poss[0] = nd.pos;
				t.poss[1] = nd.links[1].pos;
				t.poss[2] = nd.links[1].links[4].pos;

				t.uvs[0]  = nd.uv;
				t.uvs[1]  = nd.links[1].uv;
				t.uvs[2]  = nd.links[1].links[4].uv;

				this.mRenderTris.push(t);

				t = new RenderTriangle();
				t.texture = this.texture1;

				t.poss[0] = nd.pos;
				t.poss[1] = nd.links[1].links[4].pos;
				t.poss[2] = nd.links[4].pos;

				t.uvs[0]  = nd.uv;
				t.uvs[1]  = nd.links[1].links[4].uv;
				t.uvs[2]  = nd.links[4].uv;

				this.mRenderTris.push(t);
			}
		}

		this.addBGTriangles(this.mNodes[0].pos.y);
	},

	addBGTriangles: function(by) {
		var cols = 4;
		var t, x, y, sz = 110;
		var ox = -(cols*sz)/2;
		var oz = -(cols*sz)/2;

		for (y = 0;y < cols;y++) {
			for (x = 0;x < cols;x++) {
				var bv = ((x+y)&1) * 0.5;
				t = new RenderTriangle();
				t.texture = this.texture2;

				t.poss[0] = new Vec3(ox + x*sz     , by, oz + y*sz     );
				t.poss[1] = new Vec3(ox + x*sz + sz, by, oz + y*sz     );
				t.poss[2] = new Vec3(ox + x*sz     , by, oz + y*sz + sz);

				t.uvs[0]  = {u:0  , v:bv    };
				t.uvs[1]  = {u:0.5, v:bv    };
				t.uvs[2]  = {u:0  , v:bv+0.5};

				if ((x==1 || x==2) && (y==1 || y==2))
					this.modifyRoofUV(t, x == 2, bv);

				t.lighting = false;
				t.zBias = 0.5;
				this.mRenderTris.push(t);

				t = new RenderTriangle();
				t.texture = this.texture2;

				t.poss[0] = new Vec3(ox + x*sz     , by, oz + y*sz + sz);
				t.poss[1] = new Vec3(ox + x*sz + sz, by, oz + y*sz    );
				t.poss[2] = new Vec3(ox + x*sz + sz, by, oz + y*sz + sz);

				t.uvs[0]  = {u:0  , v:bv+0.5};
				t.uvs[1]  = {u:0.5, v:bv    };
				t.uvs[2]  = {u:0.5, v:bv+0.5};

				if ((x==1 || x==2) && (y==1 || y==2))
					this.modifyRoofUV(t, x == 2, bv);

				t.lighting = false;
				t.zBias = 0.5;
				this.mRenderTris.push(t);

			}
		}
	},

	modifyRoofUV: function(t, rv, bv) {
		if (rv) {
			t.uvs[0].u = 0.5 - t.uvs[0].u;
			t.uvs[1].u = 0.5 - t.uvs[1].u;
			t.uvs[2].u = 0.5 - t.uvs[2].u;
		}

		t.uvs[0].u += 0.5;
		t.uvs[1].u += 0.5;
		t.uvs[2].u += 0.5;

		if (rv) {
			t.uvs[0].v = 0.5 - t.uvs[0].v + bv + bv;
			t.uvs[1].v = 0.5 - t.uvs[1].v + bv + bv;
			t.uvs[2].v = 0.5 - t.uvs[2].v + bv + bv;
		}

	},

	transformPolygons: function() {
		var trans = new M44();
		trans.mul(this.mViewMat, this.mProjMat);

		var hw = this.mViewport.ow;
		var hh = this.mViewport.oh;

		var len = this.mRenderTris.length;
		var t;
		var spos = [0, 0, 0, 0];
		for (var i = 0;i < len;i++) {
			t = this.mRenderTris[i];
			for (var k = 0;k < 3;k++) {
				trans.transVec3(spos, t.poss[k].x, t.poss[k].y, t.poss[k].z);

				var W = spos[3];
				spos[0] /= W;
				spos[1] /= W;
				spos[2] /= W;

				spos[0] *= this.mViewport.w;
				spos[1] *= -this.mViewport.h;
				spos[0] += hw;
				spos[1] += hh;

				t.tposs[k].x = spos[0];
				t.tposs[k].y = spos[1];
				t.tposs[k].z = spos[2];
			}

			var v1 = (new Vec3()).copyFrom(t.poss[1]).sub(t.poss[0]).normalize();
			var v2 = (new Vec3()).copyFrom(t.poss[2]).sub(t.poss[1]).normalize();
			var N = (new Vec3()).cp(v1, v2);

			trans.transVec3Rot(spos, N.x, N.y, N.z);

			if (t.lighting) {
				if (spos[2] > 0)
					t.shade = 0.8
				else {
					t.shade = 0.1 - N.y * 0.6;
					if (t.shade < 0) t.shade = 0;
				}
			}

			t.sortKey = Math.floor( (t.tposs[0].z + t.tposs[1].z + t.tposs[2].z + t.zBias) *1000 );
		}
	}
}

function ClothNode()
{
	this.flags = 0;
	this.pos  = new Vec3();
	this.velo = new Vec3();
	this.cv   = new Vec3();
	this.F    = new Vec3();
	this.links = [null, null, null, null];
	this.uv = {u:0, v:0};
}

function RenderTriangle()
{
	this.texture = null;
	this.poss  = new Array(3);
	this.tposs = [new Vec3(), new Vec3(), new Vec3()];
	this.uvs = [{u:0, v:0}, {u:0, v:0}, {u:0, v:0}];
	this.shade = 0;
	this.lighting = true;
	this.zBias = 0;

	this.sortKey = 0;
}