立体上点的投影ppt课件.ppt

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1、Projectionofapoint点的投影Relativepositionoftwopointsonasolid立体上二点的相对位置Identificationandlabelingofcoincidentpoint重影点的判别与标注Exercises练习题ProjectionofPointsforaSolid立体上点的投影请点击相应标题显示其内容OProjectionofapoint点的投影1.ProjectionofthepointA空间A点的投影请点击鼠标左键显示后面内容a——ThehorizontalprojectionofthepointA点A在水平面H上的投影；a'——Th

2、efrontalprojectionofthepointA点A在正平面V上的投影；a"——TheprofileprojectionofthepointA点A在侧平面W上的投影。a'a"aZ=a'ax=a"aYw→ThedistanceofAtoH.(A点到水平面H的距离)a'a"OZTheheightalignment,Zequal.即高平齐,Z相等XYYZ2.Theprincipleofpoints点的投影规律3.Relationofpointsprojection&coordinate点的坐标与投影的关系请点击鼠标左键显示后面内容Projectionofapoint点的投影aa'

3、OXThelengthalignment,Xequal.即长对正,X相等aa"OYThewidthequality,Yequal.即宽相等,Y相等X=a'az=aaYH→ThedistanceofAtoW.(A点到侧平面W的距离)Y=aax=a"az→ThedistanceofAtoV.(A点到正平面V的距离)a'aa"axaZaYHaYWa'aa"Steps作图步骤：（1）Drawingcoordinateoriginandaxis.画出坐标原点及各轴;（2）AccordingtocoordinateofpointA,constructprojectiona',a;根据A点的坐标求其

4、V、H面的投影a',a;（3）Accordingtorulesprojectionsofpoint,drawprojectiona".根据点的投影规律求出第三投影a"。Example1.ThepointA(5,10,15).constructthreeprojectionsofA.已知A点的坐标为(5，10，15),求A点的三面投影。A请点击鼠标左键显示后面内容由于投影面的大小与视图无关。因此,在画三视图时,不必画出投影面的边框。Relativepositionoftwopoints二点的相对位置RelativepositionsofpointAB(A与B两点的相对位置)请点击鼠标左键

5、显示后面内容UpanddownZ上、下在V、W面上看坐标差ZFrontandbackY前、后在H、W面上看坐标差YLeftandrightX左、右在V、H面上看坐标差Xa'a"ab"b'AXa'a"aSteps作图步骤：（2）Constructprojectionb".根据点的投影规律求b"。Example2.PointBbelowA10,afterA5,leftA10.constructprojectionsofB.已知点B在A下10mm,A后5mm,A左10mm处,求B点的三投影。请点击鼠标左键显示后面内容AB（1）Constructprojectionb',b.根

6、据B的相对位置求投影b',b。b'b"Identification判别WhenprojectedtotheH-Plane,upcoveringdown.投影在H面上重合时，上遮下(Z坐标大的可见)。Identificationandlabelingofcoincidentpoint重影点的判别与标注请点击鼠标左键显示后面内容Labeling标注Defining定义whentwopointsonthesolidareonthesameverticallineofaprojectionplane,thetwoprojectedpointswillbethesamepointandthetwo

7、pointsarecalledthecoincidentpointoftheprojection.当两点在某一投影面上的投影重合时称为该面的重影点。WhenprojectedtotheV-Plane,frontcoveringback.投影在V面上重合时，前遮后(Y坐标大的可见)。WhenprojectedtotheW-Plane,leftcoveringright.投影在W面上重合时，左遮右(X坐标大的可见)。Allinvisib