立体上直线的投影课件.ppt

本小节结束**Projectionoflines直线的投影Characteristicsoflineprojection直线的投影特性Exercises练习题ProjectionofLinesonaSolid

立体上直线的投影请点击相应标题显示其内容Theresultofprojectionisalineconnectingtheprojectedpointsofthetwoendpointsoftheline.直线的投影由直线上两端点A、B同面投影的连线来确定。Projectionoflines直线的投影请点击鼠标左键显示后面内容bbbaaababaVHWabOabababThepartitionofpointonalinemustbeequaltoontheprojectedline.点分线段长度之比等于其投影分线段投影长度之比。Characteristicsoflineprojection直线的投影特性1.Linearity直线性：Theprojectionofalineproducesaline.直线的投影仍然是直线(特殊情况积聚为点)。2.Parallelism平行性：Theparallelismoflinesbeforeandafterprojectiondoesnotchange.平行直线的各同面投影仍然平行。3.Subordinative从属性：Theprojectionofapointonalinemustbeontheprojectedline.若点在线上,则其投影应在线的投影上。aaaaa请点击鼠标左键显示后面内容A4.Proportionality定比性：VHxoYwW-perpendicularline侧垂线Z●e?f?efe?(f?)XoYHYWαhorizontalΒistheobliqueanglesofthecorrespondinglineformedwiththefrontalplane.γprofile与H面的夹角:α；与V面的夹角:β；与W面的夹角:γ。（均为0?或90?）H-plane,H-perpendicular(铅垂线)IfitisverticaltotheV-plane,itiscalledaV-perpendicularline.(正垂线)W-plane,W-perpendicular(侧垂线)与某投影面垂直的直线称为该面的垂直线．Itsprojectiononitsverticalplaneconvergestoapoint.投影面垂直线在所垂直的投影面上的投影积聚为一点。Itsprojectionsontheothertwoplanesarebothparallelwithanaxisofprojection,andshowsitstruelength.在另外两个投影面上的投影均平行相应的投影轴，且反映实长。Definition定义Obliquity倾角Characteristics投影特性1.Verticallinesprojection投影面垂直线请点击鼠标左键显示后面内容H-perpendicularline铅垂线YW●a?b?a(b)a?b?XZoYHAB