二维与三维？
问一个最＊＊的问题：二维与三维的区别在哪里？为什么我做练习题24的时候会把那个图看成是三维呢？除了从坐标系统上来区分，还有什么方法？谢谢！ 简单的说，二维是平面，三维是立体 75185发表于2005-3-2 13:40:00static/image/common/back.gif简单的说，二维是平面，三维是立体
<BR>科学的说,二维就是由X轴和Y轴共同围成的平面坐标系
三维就是由X轴Y轴以及正对着你的Z轴围成的能反应对象所有特性的坐标系
你们说的我也知道呀，可是我为什么会把上面的图看成是三维呢？
而且到现在为至还是如此！ 因为这是一个假三维。 假三维？
如何区分呀？！ 假三维就是轴测图。 这只是你的视觉误差罢了
看看这些,是不是更让你晕????????
<IMG id=fpGalleryMainImg_9075 title="" height=429 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/3d1.jpg" width=400 name=fpGalleryMainImg_9075>
<IMG id=fpGalleryMainImg_9075 title="" style="visiblity: visible" height=420 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/A、B块的颜色是否一样？这是我看过的最具有欺骗性的一副图画了。实际上AB两块的颜色是一样的。如果不相信可以把这副图像存下来用Photoshop中的取色器查看一下就知道了。2.jpg" width=540 name=fpGalleryMainImg_9075>
<IMG id=fpGalleryMainImg_9075 title="" style="visiblity: visible" height=308 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/post-21-1050898721.jpg" width=414 name=fpGalleryMainImg_9075>
<IMG id=fpGalleryMainImg_9075 title="" style="visiblity: visible" height=540 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/post-21-1050898732.jpg" width=720 name=fpGalleryMainImg_9075>
<IMG id=fpGalleryMainImg_9075 title="" style="visiblity: visible" height=119 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/仔细看看两个图案中心的圆大小是否一样.gif" width=198 name=fpGalleryMainImg_9075>
<A style="DISPLAY: inline" href="<b>javascript</b> :fp_ShowImg(document['fpphoto_8267'],'200','229','9075',5);" target="_blank" ><IMG id=fpphoto_8267 title="" height=100 hspace=10 src="http://cyber.swnu.edu.cn/psychology/photogallery/photo00030534/仔细看看，%20是不是一个正圆.gif" width=87 align=absMiddle lowsrc=仔细看看，%20是不是一个正圆.gif vspace=5 border=0 name=fpphoto_8267></A>
<IMG id=fpGalleryMainImg_9075 title="" style="visiblity: visible" height=540 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/数数大象到底几条腿.jpg" width=720 name=fpGalleryMainImg_9075><IMG id=fpGalleryMainImg_9075 title="" style="visiblity: visible" height=340 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/数数有几个黑点.jpg" width=416 name=fpGalleryMainImg_9075>
<IMG id=fpGalleryMainImg_9075 title="" style="visiblity: visible" height=650 src="http://cyber.swnu.edu.cn/psychology/academy/xlxh/cjtp/数数有多少动物.jpg" width=429 name=fpGalleryMainImg_9075> <P class=MsoNormal style="MARGIN-LEFT: 42pt; TEXT-INDENT: -42pt; TEXT-ALIGN: center; tab-stops: list 42.0pt; mso-list: l3 level1 lfo2" align=center><B style="mso-bidi-font-weight: normal"><SPAN style="mso-list: Ignore">第四章<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN></B><B style="mso-bidi-font-weight: normal">轴测图<SPAN lang=EN-US><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></SPAN></B>
<P class=MsoNormal><o:p> </o:p>
<P class=MsoNormal style="MARGIN-LEFT: 42.25pt; TEXT-INDENT: -21pt; LINE-HEIGHT: 150%; tab-stops: list 42.25pt; mso-list: l6 level1 lfo4"><B style="mso-bidi-font-weight: normal"><SPAN style="mso-list: Ignore">一．<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN></B><B style="mso-bidi-font-weight: normal">概念<SPAN lang=EN-US><o:p></o:p></SPAN></B>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: -15.75pt; LINE-HEIGHT: 150%; tab-stops: list 47.5pt; mso-list: l1 level1 lfo6"><SPAN style="mso-list: Ignore">1.<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>投影四要素：光源、投影线、投影面、投影物体<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> （第二章内容，温习）<o:p></o:p></SPAN></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: -15.75pt; LINE-HEIGHT: 150%; tab-stops: list 47.5pt; mso-list: l1 level1 lfo6"><SPAN style="mso-list: Ignore">2.<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>生成条件：投影线互相平行（属平行投影），但投影线与任一轴<SPAN lang=EN-US>(用于描述物体几何尺度)均不平行（任一坐标轴不发生投影积聚）。<o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 88.75pt; TEXT-INDENT: 11pt; LINE-HEIGHT: 150%">当投影线垂直投影面为正轴测投影图，否则为斜轴测投影图。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: -15.75pt; LINE-HEIGHT: 150%; tab-stops: list 47.5pt; mso-list: l1 level1 lfo6"><SPAN style="mso-list: Ignore">3.<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>轴测图与视图的异同：<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt; mso-list: l2 level1 lfo8"><SPAN style="mso-list: Ignore">①<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>轴测图的投影线与任一轴不平行，一投影平面可同时反映物体三个方向长度尺寸，故一个投影图已基本反映物体形状尺寸，并有立体感。但形体表达不全面。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 63pt; LINE-HEIGHT: 150%">视图的投影线与其中一轴平行，故一投影面仅能反映物体二个方向尺度，要完整反映物体至少需要二个投影面的视图，且缺乏立体感。但能准确、完整反映物体各部分的形状。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt 63.0pt; mso-list: l2 level1 lfo8"><SPAN style="mso-list: Ignore">②<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>轴测图与视图均为平行投影，因而“与投影平面平行反映实形、与投影线平行积聚”等的投影特性仍能适用。故轴测投影特性是：<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 78.75pt; TEXT-INDENT: -15.75pt; LINE-HEIGHT: 150%; tab-stops: list 78.75pt; mso-list: l7 level1 lfo10"><SPAN style="mso-list: Ignore">a.<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>空间互相平行的直线在轴测投影仍然互相平行，因此形体上平行于三个坐标轴的线段的轴测投影与轴测轴平行。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 78.75pt; TEXT-INDENT: -15.75pt; LINE-HEIGHT: 150%; tab-stops: list 78.75pt; mso-list: l7 level1 lfo10"><SPAN style="mso-list: Ignore">b.<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>空间互相平行的两线段的长度之比等于它们投影长度之比。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 42.5pt; TEXT-INDENT: 20.5pt; LINE-HEIGHT: 150%">这两投影特性是绘画轴测图的依据。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: -15.75pt; LINE-HEIGHT: 150%; tab-stops: list 47.5pt; mso-list: l1 level1 lfo6"><SPAN style="mso-list: Ignore">4.<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>有关概念<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 49.5pt 58.5pt; mso-list: l5 level1 lfo12"><SPAN style="mso-list: Ignore">①<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>轴测轴<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> 描述物体长、宽、高的坐标轴在轴测投影面的投影。 <o:p></o:p></SPAN></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 49.5pt 58.5pt; mso-list: l5 level1 lfo12"><SPAN style="mso-list: Ignore">②<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>轴间角<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> 轴测轴之间的夹角。<o:p></o:p></SPAN></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt; mso-list: l5 level1 lfo12"><SPAN style="mso-list: Ignore">③<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>轴向变形系数<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> 轴向线段的投影长度与实际长度之比。当三个轴向变形系数相同时，为等测；只有两个轴的变形系数相同，则为二测。<o:p></o:p></SPAN></SPAN>
<P class=MsoNormal style="LINE-HEIGHT: 150%"><o:p> </o:p>
<P class=MsoNormal style="MARGIN-LEFT: 21.25pt; LINE-HEIGHT: 150%"><B style="mso-bidi-font-weight: normal">二．轴测图的绘画<SPAN lang=EN-US><o:p></o:p></SPAN></B>
<P class=MsoNormal style="LINE-HEIGHT: 150%"><SPAN style="mso-tab-count: 1"> 1. 轴测图的类型及其特点<o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt; mso-list: l0 level1 lfo14"><SPAN style="mso-list: Ignore">①<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>正等测<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> 投影线与三个坐标轴夹角相等（任一坐标平面与投影面均不平行），并与投影面垂直。<o:p></o:p></SPAN></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: 16.25pt; LINE-HEIGHT: 150%">轴间角<SPAN lang=EN-US><SPAN style="mso-tab-count: 2"> </SPAN></SPAN>∠XOY＝∠YOZ＝∠XOZ＝<SPAN lang=EN-US>120</SPAN>°<o:p></o:p>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: 16.25pt; LINE-HEIGHT: 150%">轴向变形系数<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> </SPAN></SPAN>OX轴：<SPAN lang=EN-US>1.0<SPAN style="mso-tab-count: 3"> </SPAN></SPAN>OY轴：<SPAN lang=EN-US>1.0<SPAN style="mso-tab-count: 2"> </SPAN></SPAN>OZ轴：<SPAN lang=EN-US>1.0<o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt; mso-list: l0 level1 lfo14"><SPAN style="mso-list: Ignore">②<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>斜二测<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> 一含有高度的物体表面（如</SPAN></SPAN>X<SUB>1</SUB>O<SUB>1</SUB>Z<SUB>1</SUB>平面）与投影面平行（投影为实形），投影线与投影平面倾斜。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: 16.25pt; LINE-HEIGHT: 150%">轴间角<SPAN lang=EN-US><SPAN style="mso-tab-count: 2"> </SPAN></SPAN>∠XOY＝45°<SPAN style="mso-tab-count: 2"> </SPAN>∠YOZ＝<SPAN lang=EN-US>45</SPAN>°<SPAN style="mso-tab-count: 2"> </SPAN>∠XOZ＝<SPAN lang=EN-US>90</SPAN>°<o:p></o:p>
<P class=MsoNormal style="MARGIN-LEFT: 47.5pt; TEXT-INDENT: 16.25pt; LINE-HEIGHT: 150%">轴向变形系数<SPAN lang=EN-US><SPAN style="mso-spacerun: yes"> </SPAN></SPAN>OX轴：<SPAN lang=EN-US>1.0<SPAN style="mso-tab-count: 3"> </SPAN></SPAN>OY轴：<SPAN lang=EN-US>0.5<SPAN style="mso-tab-count: 2"> </SPAN></SPAN>OZ轴：<SPAN lang=EN-US>1.0<o:p></o:p></SPAN>
<P class=MsoNormal style="LINE-HEIGHT: 150%"><SPAN style="mso-spacerun: yes"> 2. 绘画轴测图的要点<o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt 68.25pt; mso-list: l4 level1 lfo16"><SPAN style="mso-list: Ignore">①<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>根据坐标轴与投影面和投影线与投影面的相对位置（轴测图的类型）画出轴测轴。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt 68.25pt; mso-list: l4 level1 lfo16"><SPAN style="mso-list: Ignore">②<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>只有轴向的投影与实长之比是可知的，因此在轴测图可直接确定长度的线段必须与轴平行。所以轴测图的控制点是由与轴测轴平行和由变形系数两因素确定。即先确定物体各角点到坐标平面的距离，然后根据变形系数将角点放到投影平面上。对于回转体，则是将物体表面的圆心和平行投影轴的直径或半径放到投影面上。<SPAN lang=EN-US><o:p></o:p></SPAN>
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt 68.25pt; mso-list: l4 level1 lfo16"><SPAN style="mso-list: Ignore">③<SPAN style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN>依次连接各控制点可得物体的轴测图。
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt 68.25pt; mso-list: l4 level1 lfo16">嘿嘿，谢谢两位！这是我在网上找到的。
<P class=MsoNormal style="MARGIN-LEFT: 58.5pt; TEXT-INDENT: -18pt; LINE-HEIGHT: 150%; tab-stops: list 58.5pt 68.25pt; mso-list: l4 level1 lfo16">第一幅图让我看的最晕！ 有意思
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