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<p align="center"><b><font SIZE="5" FACE="標(biāo)楷體">M</font><font SIZE="4" FACE="標(biāo)楷體">ATLAB</font><font SIZE="5" FACE="標(biāo)楷體"> 程式設(shè)計(jì)與應(yīng)用</font></b>
</p>
<h1><font SIZE="4" FACE="標(biāo)楷體"><b>3.基本XYZ立體繪圖命令 <br>
</b></font></h1>
<p><font FACE="標(biāo)楷體">在科學(xué)目視表示(Scientific visualization)中,三度空間的立體圖是一個(gè)非常重要的技巧。本章將介紹MATLAB基本XYZ三度空間的各項(xiàng)繪圖命令。
<br>
</font></p>
<p><font FACE="標(biāo)楷體">mesh和plot是三度空間立體繪圖的基本命令,mesh可畫出立體網(wǎng)狀圖,plot則可畫出立體曲面圖,兩者產(chǎn)生的圖形都會(huì)依高度而有不同顏色。下列命令可畫出由函數(shù)<img SRC="images/img00001.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00001.GIF" WIDTH="86" HEIGHT="23">形成的立體網(wǎng)狀圖:
<br>
</font></p>
<p><a NAME="INPUT_50"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">x=linspace(-2,
2, 25); % </font></tt><font SIZE="2" COLOR="#008000">在</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">x</font></tt><font SIZE="2" COLOR="#008000">軸上取</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">25</font></tt><font SIZE="2" COLOR="#008000">點(diǎn)</font></a>
</p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">y=linspace(-2, 2, 25); % </font></tt><font SIZE="2" COLOR="#008000">在</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">y</font></tt><font SIZE="2" COLOR="#008000">軸上取</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">25</font></tt><font SIZE="2" COLOR="#008000">點(diǎn)</font> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">[xx,yy]=meshgrid(x, y); % xx</font></tt><font SIZE="2" COLOR="#008000">和</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">yy</font></tt><font SIZE="2" COLOR="#008000">都是</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">21x21</font></tt><font SIZE="2" COLOR="#008000">的矩陣</font> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">zz=xx.*exp(-xx.^2-yy.^2); % </font></tt><font SIZE="2" COLOR="#008000">計(jì)算函數(shù)值,</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">zz</font></tt><font SIZE="2" COLOR="#008000">也是</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">21x21</font></tt><font SIZE="2" COLOR="#008000">的矩陣</font> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">mesh(xx, yy, zz); % </font></tt><font SIZE="2" COLOR="#008000">畫出立體網(wǎng)狀圖<tt> </tt></font></p>
<p><a NAME="OUTPUT_50"><img SRC="images/img00002.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00002.GIF" WIDTH="382" HEIGHT="286"><font SIZE="2" COLOR="#0000FF"><tt> </tt></font></a><font SIZE="2"><br>
</font></p>
<p><font FACE="標(biāo)楷體">surf和mesh的用法類似: <br>
</font></p>
<p><a NAME="INPUT_77"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">x=linspace(-2,
2, 25); % </font></tt><font SIZE="2" COLOR="#008000">在</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">x</font></tt><font SIZE="2" COLOR="#008000">軸上取</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">25</font></tt><font SIZE="2" COLOR="#008000">點(diǎn)</font></a>
</p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">y=linspace(-2, 2, 25); % </font></tt><font SIZE="2" COLOR="#008000">在</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">y</font></tt><font SIZE="2" COLOR="#008000">軸上取</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">25</font></tt><font SIZE="2" COLOR="#008000">點(diǎn)</font> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">[xx,yy]=meshgrid(x, y); % xx</font></tt><font SIZE="2" COLOR="#008000">和</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">yy</font></tt><font SIZE="2" COLOR="#008000">都是</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">21x21</font></tt><font SIZE="2" COLOR="#008000">的矩陣</font> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">zz=xx.*exp(-xx.^2-yy.^2); % </font></tt><font SIZE="2" COLOR="#008000">計(jì)算函數(shù)值,</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">zz</font></tt><font SIZE="2" COLOR="#008000">也是</font><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">21x21</font></tt><font SIZE="2" COLOR="#008000">的矩陣</font> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">surf(xx, yy, zz); % </font></tt><font SIZE="2" COLOR="#008000">畫出立體曲面圖<tt> </tt></font></p>
<p><a NAME="OUTPUT_77"><img SRC="images/img00003.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00003.GIF" WIDTH="382" HEIGHT="286"><font SIZE="2" COLOR="#0000FF"><tt> </tt></font></a><font SIZE="2"><br>
<br>
</font></p>
<p><font FACE="標(biāo)楷體">為了方便測(cè)試立體繪圖,MATLAB提供了一個(gè)peaks函數(shù),可產(chǎn)生一個(gè)凹凸有致的曲面,包含了三個(gè)局部極大點(diǎn)及三個(gè)局部極小點(diǎn),其方程式為:</font>
</p>
<p><img SRC="images/img00004.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00004.GIF" WIDTH="388" HEIGHT="42"> </p>
<p><font FACE="標(biāo)楷體">要畫出此函數(shù)的最快方法即是直接鍵入peaks: <br>
</font></p>
<p><a NAME="INPUT_78"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">peaks </font></tt></a></p>
<p><a NAME="OUTPUT_78"></a> </p>
<p><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New">z = 3*(1-x).^2.*exp(-(x.^2) -
(y+1).^2) ... </font></tt></p>
<p><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New">- 10*(x/5 - x.^3 -
y.^5).*exp(-x.^2-y.^2) ... </font></tt></p>
<p><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New">- 1/3*exp(-(x+1).^2 - y.^2) </font></tt></p>
<p><img SRC="images/img00005.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00005.GIF" WIDTH="382" HEIGHT="286"><font SIZE="2"> <br>
</font></p>
<p><font FACE="標(biāo)楷體">我們亦可對(duì)peaks函數(shù)取點(diǎn),再以各種不同方法進(jìn)行繪圖。meshz可將曲面加上圍裙:
<br>
</font></p>
<p><a NAME="INPUT_80"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">[x,y,z]=peaks;</font></tt></a>
</p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">meshz(x,y,z);</font></tt> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">axis([-inf inf -inf inf -inf
inf]); </font></tt></p>
<p><a NAME="OUTPUT_80"><img SRC="IMG00006.GIF" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00006.GIF"><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New"> </font></tt></a><font SIZE="2"><br>
</font></p>
<p><font FACE="標(biāo)楷體">waterfall可在x方向或y方向產(chǎn)生水流效果: <br>
</font></p>
<p><a NAME="INPUT_81"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">[x,y,z]=peaks;</font></tt></a>
</p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">waterfall(x,y,z);</font></tt> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">axis([-inf inf -inf inf -inf
inf]); </font></tt></p>
<p><a NAME="OUTPUT_81"><img SRC="images/img00007.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00007.GIF" WIDTH="382" HEIGHT="286"><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New"> </font></tt></a><font SIZE="2"><br>
</font></p>
<p><font FACE="標(biāo)楷體">下列命令產(chǎn)生在y方向的水流效果: <br>
</font></p>
<p><a NAME="INPUT_82"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">[x,y,z]=peaks;</font></tt></a>
</p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">waterfall(x',y',z');</font></tt> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">axis([-inf inf -inf inf -inf
inf]); </font></tt></p>
<p><a NAME="OUTPUT_82"><img SRC="images/img00008.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00008.GIF" WIDTH="382" HEIGHT="286"><font SIZE="2"> </a><br>
</font></p>
<p><font FACE="標(biāo)楷體">meshc同時(shí)畫出網(wǎng)狀圖與等高線: <br>
</font></p>
<p><a NAME="INPUT_85"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">[x,y,z]=peaks;</font></tt></a>
</p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">meshc(x,y,z); </font></tt></p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">axis([-inf inf -inf inf -inf
inf]); </font></tt></p>
<p><a NAME="OUTPUT_85"><img SRC="images/img00009.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00009.GIF" WIDTH="382" HEIGHT="286"><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New"> </font></tt></a><font SIZE="2"><br>
</font></p>
<p><font FACE="標(biāo)楷體">surfc同時(shí)畫出曲面圖與等高線: <br>
</font></p>
<p><a NAME="INPUT_90"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">[x,y,z]=peaks;</font></tt></a>
</p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">surfc(x,y,z); </font></tt></p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">axis([-inf inf -inf inf -inf
inf]); </font></tt></p>
<p><a NAME="OUTPUT_90"><img SRC="images/img00010.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00010.GIF" WIDTH="382" HEIGHT="286"><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New"> </font></tt></a><font SIZE="2"><br>
</font></p>
<p><font FACE="標(biāo)楷體">contour3畫出曲面在三度空間中的等高線: <br>
</font></p>
<p><a NAME="INPUT_89"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">contour3(peaks,
20);</font></tt></a> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">axis([-inf inf -inf inf -inf
inf]); </font></tt></p>
<p><a NAME="OUTPUT_89"><img SRC="images/img00011.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00011.GIF" WIDTH="382" HEIGHT="286"><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New"> </font></tt></a><font SIZE="2"><br>
</font></p>
<p><font FACE="標(biāo)楷體">contour畫出曲面等高線在XY平面的投影: <br>
</font></p>
<p><a NAME="INPUT_91"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">contour(peaks,
20); </font></tt></a></p>
<p><a NAME="OUTPUT_91"><img SRC="images/img00012.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00012.GIF" WIDTH="382" HEIGHT="286"><tt><font SIZE="2" COLOR="#0000FF" FACE="Courier New"> </font></tt></a><font SIZE="2"><br>
</font></p>
<p><font FACE="標(biāo)楷體">plot3可畫出三度空間中的曲線: <br>
</font></p>
<p><a NAME="INPUT_86"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">t=linspace(0,20*pi,
501);</font></tt></a> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">plot3(t.*sin(t), t.*cos(t), t); </font></tt></p>
<p><a NAME="OUTPUT_86"><img SRC="images/img00013.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00013.GIF" WIDTH="382" HEIGHT="286"><font SIZE="2"> </a><br>
</font></p>
<p><font FACE="標(biāo)楷體">亦可同時(shí)畫出兩條三度空間中的曲線:<br>
</font></p>
<p><a NAME="INPUT_87"><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">t=linspace(0,
10*pi, 501);</font></tt></a> </p>
<p><tt><font SIZE="2" COLOR="#008000" FACE="Courier New">plot3(t.*sin(t), t.*cos(t), t,
t.*sin(t), t.*cos(t), -t); </font></tt></p>
<p><a NAME="OUTPUT_87"><img SRC="images/img00014.gif" tppabs="http://ins22web.seu.edu.cn/xuray/netschool/mlbook/IMG00014.GIF" WIDTH="382" HEIGHT="286"><font SIZE="2"> </a><br>
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