主要困难点在衣服褶皱的表现上面被，可以参考一下达芬奇的画
参考：http://www.zhihu.com/question/21214264?sort=created
http://image.baidu.com/i?ct=503316480&z=0&tn=baiduimagedetail&ipn=d&word=%E8%BE%BE%E8%8A%AC%E5%A5%87%20%E8%A1%A3%E6%9C%8D%E8%A4%B6%E7%9A%B1%E8%81%94%E7%B3%BB&step_word=&pn=0&spn=0&di=89149967170&rn=1&is=&istype=&ie=utf-8&oe=utf-8&in=12821&cl=2&lm=-1&st=&cs=1134556225%2C1789729059&os=887455061%2C2889217826&ln=1147&fr=&fmq=1407741341951_R&ic=&s=&se=&sme=0&tab=&width=&height=&face=&ist=&jit=&cg=&objurl=http%3A%2F%2Fd.hiphotos.baidu.com%2Fzhidao%2Fpic%2Fitem%2F4610b912c8fcc3ce7065ebb19245d688d53f208e.jpg&fromurl=ippr_z2C%24qAzdH3FAzdH3Fzit1w5_z%26e3Bkwt17_z%26e3Bv54AzdH3Fq7jfpt5gAzdH3F909cl8aad_z%26e3Bip4s
