螺旋式上升的图形怎么画啊。。 类似这种 http://images.google.co.jp/imglanding?q=%E8%9E%BA%E6%97%8B%E5%BC%8F%E4%B8%8A%E5%8D%87%20%E4%BD%9C%E5%9B%BE&imgurl=http://news.ynet.com/img.db%3F57048479%2Bs(450x400)%2Bpart(0,0,450,400)&imgrefurl=http://news.ynet.com/view.jsp%3Foid%3D57048456&usg=__1LxmYL_CrwMVec-pO4oeXsqJlsU=&h=400&w=294&sz=84&hl=ja&um=1&itbs=1&tbnid=9bpxXVBszgwbhM:&tbnh=124&tbnw=91&prev=/images%3Fq%3D%25E8%259E%25BA%25E6%2597%258B%25E5%25BC%258F%25E4%25B8%258A%25E5%258D%2587%2B%25E4%25BD%259C%25E5%259B%25BE%26um%3D1%26hl%3Dja%26lr%3Dlang_zh-CN%26rls%3Dcom.microsoft:ja:IE-SearchBox%26rlz%3D1I7GGLL_ja%26tbs%3Disch:1&um=1&lr=lang_zh-CN&rls=com.microsoft:ja:IE-SearchBox&rlz=1I7GGLL_ja&tbs=isch:1&start=0#tbnid=9bpxXVBszgwbhM&start=1