正投影法原理ppt课件.ppt

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1、FormofProjection投影的形成TypesofProjection投影法分类FeaturesofOrthographicProjection正投影特性Three-viewofComponent物体的三视图Exercises练习题PrinciplesofOrthographicProjection正投影法原理请点击相应标题显示其内容CenterofprojectionPlaneofprojectionObjectLinesofprojectionProjectionFormofProjection投影的形成Projectionmethod:Whent

2、helineofprojectionpassesthroughtheobjectandthepre-establishedplane,therewillbegraphicsproducedontheplane.Thismethodiscalledprojection.投影法：投影法是投射线通过物体，向选定的平面投射，并在该面上得到图形的方法。请点击鼠标左键显示后面内容TypesofProjection投影法分类Projectionmethod投影法Centralprojectionmethod中心投影法(Thecentralprojectionismainl

3、yusedforthepictorialdrawingsofbuildings.一般多用于建筑图样)Parallelprojectionmethod平行投影法(Itisusedinmostengineeringdrawings.广泛用于机械、电子、化工等行业的图样)请点击鼠标左键显示后面内容3.Homophyly:Whenplanarfeaturesorlinesareinclinedtothe类似性projectionplaneingeneral,theprojectionproducessimilarshapesoftheoriginalfeature.

4、Thelengthofprojectedlineswillbeshorterthanthereallength.当图形或直线倾斜于投影面时，图形的投影成类似形,线段的投影长度比实长短。2.Accumulation:Whenplanarfeaturesorlinesareorthogonaltothe积聚性projectionplane,theprojectionaccumulatestoalineorapoint.当图形或直线垂直于投影面时,其投影积聚成一直线或点。1.Authenticity:Whenplanarfeaturesorlinesareinpa

5、rallelwiththe真实性projectionplane,theprojectionshowstherealshapeortruelengthofthefeaturesbeingprojected.当平面图形或直线平行于投影面时,其投影反映实形或实长。FeaturesofOrthographicProjection正投影特性请点击鼠标左键显示后面内容1.Formofthree-viewdrawings三视图的形成Three-ViewofComponent物体的三视图请点击鼠标左键显示后面内容Singleorthographicprojection单面正

6、投影Howshallwedoit?如何解决？Aplanofanobjectisnotalwayssufficienttodescribeitcompletely.仅有物体的一个投影不能确定它的空间形状。Additionalorthographicviewscanbedrawntosufficientlydescribeanobject.Itisnecessarytousemultipleviewsinengineeringdrawings.为了确定物体的空间形状,需要增加投影面。故在工程图样中多采用多面视图。Theseaxesmeetatapointwhic

7、hiscalledtheorigin.三投影轴垂直相交于原点O.Y-axis→Y轴Three-ViewofComponent物体的三视图请点击鼠标左键显示后面内容1)Setupthree-viewprojectionsystem建立三面投影体系Thethreeprojectionplanesareorthogonalfromeachother.Makeupofoneprojectionsystem.采用三个相互垂直的投影面,构成投影体系。V-plane→Verticalplane正(垂直)平面H-plane→Horizontalplane水平面W-plane

8、→Wall(Auxiliaryvertical)pl