2.Parallel line of a projection plane 投影面平行线 H-plane, horizontal (水平线) Definition If it is parallel with the V-plane,it is called a frontal line. (正平线) 定义 W-plane, profile (侧平线) 与某投影面平行的直线称为该面的平行线. horizontal Obliquity Bis the oblique angles of the corresponding line formed with the frontal plane. 倾角 profile 与H面的夹角：a;与V面的夹角：B;与W面的夹角：y。(总有一个为0°) Characteristics Shows its true length and the inclination angles formed with the axes of projection show the oblique formed with the other two planes of projection. 投影特性 在所平行的面上的投影反映实长，且反映其对另外两投影面的倾角。 Its projections on the other two projection planes are shorter than its true length,and are all vertical to the axis of projection. 在另外两个投影面上的投影长度比实长短，且垂直于相应的投影轴， Horizontal line水平线 Frontal line正平线 Profile line侧平线 a" AB Z a"AB 2.Parallel line of a projection plane 投影面平行线 β α Obliquity 倾 角 α horizontal βis the oblique angles of the corresponding line formed with the frontal plane. γ profile 与H面的夹角:α;与V 面的夹角:β;与W面的夹角:γ。(总有一个为0) Definition 定 义 Characteristics 投影特性 请 点 击 鼠 标 左 键 显 示 后 面 内 容 H-plane, horizontal (水平线) If it is parallel with the V-plane, it is called a frontal line. (正平线) W-plane, profile (侧平线) 与某投影面平行的直线称为该面的平行线． Shows its true length and the inclination angles formed with the axes of projection show the oblique formed with the other two planes of projection. 在所平行的面上的投影反映实长,且反映其对另外两投影面的倾角。 Its projections on the other two projection planes are shorter than its true length, and are all vertical to the axis of projection. 在另外两个投影面上的投影长度比实长短,且垂直于相应的投影轴。 b a b b a a X YW Z YH Horizontal line 水平线 Profile line 侧平线 X Z YW YH b a a a b b Frontal line 正平线 X YW b a b a a b Z YH AB AB AB β γ α γ