详细介绍HTML5 3D衣服摇摆动画特效如何实现

这又是一款基于HTML5 Canvas的3D动画杰作，它是一个可以随风飘动的3D衣服摇摆动画特效，非常逼真。当我们将鼠标滑过衣服时，衣服将会出现摇摆的动画，点击鼠标时，衣服将会更加剧烈地摆动。

在线演示源码下载

HTML代码

<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>

P3D库JS代码，主要用来处理3D效果的

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)	{
		retur