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📄 4.2.3 取样方式.htm

📁 计算机图形学教程计算机图形学教程
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<H3 style="TEXT-INDENT: 0cm"><FONT face=楷体_GB2312 size=4><SPAN 
style="mso-fareast-language: ZH-CN"><SPAN lang=EN-US>4.2.3 </SPAN><SPAN 
style="FONT-FAMILY: 楷体_GB2312; mso-fareast-language: ZH-CN; mso-ascii-font-family: 'Times New Roman'">取样方式</SPAN></SPAN><SPAN 
lang=EN-US style="mso-fareast-language: ZH-CN"><o:p></o:p></SPAN></FONT></H3>
<P class=MsoBodyTextIndent><SPAN style="mso-fareast-language: ZH-CN"><FONT 
face=楷体_GB2312 
size=4>一旦对一台或多台设备设置了取样方式，立即就可以进行数据输入，而不必等待程序中的输入语句。如操纵杆已被置成在取样方式下的定位设备，则操纵杆的当前位置坐标立即就被存储起来，如操纵杆的位置在变化，就立即用当前的坐标来代替以前位置的坐标值，当应用程序一遇到取样命令，就把相应物理设备的值作为取样数值。设置定位设备为取样方式的命令是：<SPAN 
lang=EN-US><o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 
size=4>sample_locator(ws,device_code,x,y)<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN 
style="mso-fareast-language: ZH-CN"><FONT face=楷体_GB2312 
size=4>对其他逻辑设备设置为取样方式的命令都与此类似。<SPAN 
lang=EN-US><o:p></o:p></SPAN></FONT></SPAN></P>
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      lang=EN-US style="FONT-SIZE: 9pt"> 4.2.2 </SPAN><SPAN 
      style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">采样方式的工作过程</SPAN></P></DIV><![if !mso]></TD></TR></TBODY></TABLE><![endif]></v:textbox><w:wrap 
type = "square"></w:wrap></v:shape><![endif]--><![if !vml]><img width=230 height=33src="les423.files/image003.gif" align=left hspace=12alt="文本框: 图 4.2.2 采样方式的工作过程" v:shapes="_x0000_s1028"><![endif]><SPAN 
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<P class=MsoBodyTextIndent><SPAN style="mso-fareast-language: ZH-CN"><FONT 
face=楷体_GB2312 size=4>采样方式的工作过程如图<SPAN 
lang=EN-US>4.2.2所示。在采样模式输入过程中，程序和输入设备分别同时运行。输入设备不断地产生数据，并把数据输入数据缓存区，从而不断刷新数据缓存区的内容。程序在运行中当遇到采样语句，就到数据缓存存储区中去取数据，当然，所取的是最新刷新的输入数据。<o:p></o:p></SPAN></FONT></SPAN></P>
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<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><A 
href="http://www.ekany.com/wdg98/cg/contents/chapter4/les422.htm"><SPAN 
style="mso-fareast-language: ZH-CN"><FONT face=楷体_GB2312 
size=4>&lt;上一节&gt;</FONT></SPAN><FONT face=楷体_GB2312 size=4><SPAN 
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lang=EN-US style="mso-fareast-language: ZH-CN"> </SPAN><SPAN lang=EN-US><A 
href="http://www.ekany.com/wdg98/cg/contents/chapter4/les424.htm"><SPAN 
style="mso-fareast-language: ZH-CN">&lt;下一节&gt; </SPAN></A></SPAN><SPAN 
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