Draw symmetry lines and the base of the pyramid 先画锥底面形状.PPT

本 小 节 结 束 * * * Summary of Polyhedral Solids 平面立体概述 Prism 棱柱 Pyramid 棱锥 Exercise 练习题 Projection of Polyhedral Solids平面立体的投影 请点击相应标题显示其内容 Summary of Polyhedral Solids 平面立体概述 Prisms 棱柱 Intersection lines of edge planes are called edge lines. Intersection lines of edge planes and bases are called base edge lines. When drawing projections of polyhedral solids, we are actually drawing the projections of all edge lines and base edge lines followed by a visibility test of the projected edge lines and base edge lines. 各棱面的交线称为棱线,棱面与底面的交线称为底边,画平面立 体的投影图,实质是画出所有棱线和底边的投影,并判别其可见性。 Pyramids 棱锥 Polyhedral solids 平面立体 请点击鼠标左键显示后面内容 Polyhedral solids: The solids that are surrounded by planes are called polyhedral solids. 平面立体: 完全由平面围成的立体称为平面立体。 Class by the bases of prisms 根据棱柱底面形状可分为: Triangular prism 三棱柱 Prism 棱柱 Square prism 四棱柱 Pentagonal prism 五棱柱 Hexagonal prism 六棱柱 Draw steps 画图步骤： Draw centerlines and datum lines. 先画中心线和基准线; Add lines for the upper and lower (end) faces. 再画反映顶部或底部(端面)形状的视图; Complete three views. 按三等规律画全三视图。 请点击鼠标左键显示后面内容 五棱柱的投影演示 1. Projection of a prism 棱柱的投影 …… Example3. Draw the pentagonal prism and get points on the surface. 画五棱柱及表面上各点的三视图。 The projection of point is not visible when it is on invisible edge or plane. 凡在不可见表面及棱线上的点,其投影则为不可见。 Identification 判别: The projection of point is also visible when it is on visible edge or plane. 凡在可见表面及棱线上的点,其投影为可见; Method 方法: Getting points on surfaces of a prism can be based on the accumulation characteristics of edge lines or plane projection. 棱柱表面上的点可利用棱线或棱面的积聚性投影求之。 2.Getting points on the surface of a prism 棱柱表面上取点 Labeling 标注: All invisible points are written in brackets. 对不可见的点加括号以示区别。 请 点 击 鼠 标 左