Form of ProjectionForm of Projection 投影的形成

Types of Projection Types of Projection 投影法分类

Features of Orthographic ProjectionFeatures of Orthographic Projection 正投影特性

Three-view of Component Three-view of Component 物体的三视图

ExercisesExercises 练习题

Principles of Orthographic Projection 正 投 影 法 原 理

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Center of projectionCenter of projection

Plane of projectionPlane of projection

ObjectObject

Lines of projectionLines of projection

ProjectionProjection

Form of ProjectionForm of Projection 投影的形成投影的形成Projection method : Projection method : When the line of projection passes through the When the line of projection passes through the object and the pre - established plane, there will be graphics object and the pre - established plane, there will be graphics produced on the plane. This method is called projection. produced on the plane. This method is called projection.

投影法投影法 ： ： 投影法是投射线通过物体，向选定的平面投射，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。并在该面上得到图形的方法。

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Types of Projection Types of Projection 投影法分类投影法分类

Projection methodProjection method投影法投影法

Central projection method 中心投影法(( The central projection is mainly used for the pictorial The central projection is mainly used for the pictorial drawings of buildings.drawings of buildings. 一般多用于建筑图样一般多用于建筑图样 ))

Parallel projection method 平行投影法(( It is used in most engineering drawings.It is used in most engineering drawings.

广泛用于机械、电子、化工等行业的图样广泛用于机械、电子、化工等行业的图样 ))

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3. 3. Homophyly: When planar features or lines are inclined to theHomophyly: When planar features or lines are inclined to the 类似性类似性 projection plane in general, the projection produces projection plane in general, the projection produces similar shapes of the original feature. The length of similar shapes of the original feature. The length of projected lines will be shorter than the real length.projected lines will be shorter than the real length. 当图形或直线倾斜于投影面时，图形的投影成类似形当图形或直线倾斜于投影面时，图形的投影成类似形 ,, 线 线 段的投影长度比实长短段的投影长度比实长短。 。

2.2. Accumulation: When planar features or lines are orthogonal to theAccumulation: When planar features or lines are orthogonal to the 积聚性 积聚性 projection plane, the projection accumulates to a projection plane, the projection accumulates to a line or a point.line or a point. 当图形或直线垂直于投影面时当图形或直线垂直于投影面时 ,, 其投影积聚成一直线或点。其投影积聚成一直线或点。

1. 1. Authenticity: When planar features or lines are in parallel with the Authenticity: When planar features or lines are in parallel with the 真实性真实性 projection plane, the projection shows the real shape projection plane, the projection shows the real shape or true length of the features being projected.or true length of the features being projected. 当平面图形或直线平行于投影面时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。其投影反映实形或实长。

Features of Orthographic ProjectionFeatures of Orthographic Projection 正投影特性正投影特性

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1.1. Form of three-view drawingsForm of three-view drawings 三视图的形成三视图的形成

Three-View of Component Three-View of Component 物体的三视图物体的三视图

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Single orthographic projection单面正投影单面正投影

A plan of an object is not always sufficient to describe it completely.

仅有物体的一个投影不能确定 它的空间形状。

Additional orthographic views can be drawn to sufficiently describe an object. It is necessary to use multiple views in engineering drawings. 为了确定物体的空间形状为了确定物体的空间形状 ,, 需要增加投影面。故在工程需要增加投影面。故在工程图样中多采用多面视图。图样中多采用多面视图。

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These axes meet at a point These axes meet at a point which is called the origin.which is called the origin. 三三投影轴垂直相交于原点投影轴垂直相交于原点 OO..

Y-axis→Y 轴

0X

Y

Z V

H

W

Three-View of Component Three-View of Component 物体的三视图物体的三视图

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1) Set up three-view projection system 建立三面投影体系建立三面投影体系The three projection planes are orthogonal from The three projection planes are orthogonal from each other.each other. Make up of one projection system.Make up of one projection system.采用三个相互垂直的投影面采用三个相互垂直的投影面 ,, 构成投影体系。构成投影体系。

V-plane → Vertical plane 正 ( 垂直 ) 平面H-plane → Horizontal plane 水平面

W-plane→ Wall(Auxiliary vertical) plane 侧 ( 辅助垂直 ) 平面

The intersection lines of the The intersection lines of the three projection planes are three projection planes are called the axes of projection.called the axes of projection. 三投影面的交线为投影轴三投影面的交线为投影轴

X-axis→X 轴

Z-axis→Z 轴

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To draw three-view drawings on a drawing sheetTo draw three-view drawings on a drawing sheet将三投影面展成一个平面将三投影面展成一个平面 The V-Plane is first fixed. VV 面不动面不动 The The HH-Plane turns down 90-Plane turns down 90.. HH 面向下转面向下转 9090,,YY 轴记为轴记为 YYH H ,, The The WW-Plane turns right 90-Plane turns right 90.. WW 面向右转面向右转 9090,,YY 轴记为轴记为 YYWW 。。

The drawing produced on the profile projection plane (The drawing produced on the profile projection plane (WW-Plane).-Plane).由左向右由左向右观察将物体向观察将物体向 WW 面投影而得到的视图面投影而得到的视图。。

2) Draw three views 画三视图画三视图Front viewFront view主主视图视图：Top viewTop view俯俯视图视图 ::

The drawing produced on the frontal plane (The drawing produced on the frontal plane (VV-Plane).-Plane).由前向后由前向后观察将物体向观察将物体向 VV 面投影而得到的视图；面投影而得到的视图；

The drawing produced on the horizontal projection plane (The drawing produced on the horizontal projection plane (HH--Plane)Plane)由上向下由上向下观察将物体向观察将物体向 HH 面投影而得到的视图面投影而得到的视图；；

Llft viewLlft view左左视图视图 ::

X

Y

Z

V

H

W

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Three-View of Component Three-View of Component 物体的三视图物体的三视图

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Z

X 0 YW

YH

V W

H

2. 2. View positions and rules for producing three-view drawingsView positions and rules for producing three-view drawings 三视图的位置关系和投影规律三视图的位置关系和投影规律11)) Positions Positions 位置关系位置关系 22)) RulesRules 投影规律投影规律

4545°°

The height of the front view The height of the front view and the left-side view shouldand the left-side view shouldbe aligned and is equal.be aligned and is equal.

主、侧视图主、侧视图高平齐高平齐；；

The width of the top view The width of the top view and the left-side view shouldand the left-side view shouldalso be aligned and is equal.also be aligned and is equal.

俯、侧视图俯、侧视图宽相等宽相等。。

The length of the front view The length of the front view and the top view shouldand the top view shouldbe aligned and is equal.be aligned and is equal.

主、俯视图主、俯视图长对正长对正；；

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Three-View of Component Three-View of Component 物体的三视图物体的三视图

Front viewFront view 主视图主视图

Left-side viewLeft-side view 侧视图侧视图

Length alignLength align

长对正长对正

Height alignHeight align

高平齐高平齐

Width equalityWidth equality

宽相等宽相等Top viewTop view 俯视图俯视图

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(( 图线有重合时的优先顺序为：粗实线、虚线、细点图线有重合时的优先顺序为：粗实线、虚线、细点画线、双点画线、细实线画线、双点画线、细实线 ))

1) Define the scale, select the size of drawing sheet.1) Define the scale, select the size of drawing sheet. 确定图幅和比例；确定图幅和比例； 22) Choose a direction for front view projection. ) Choose a direction for front view projection. 确定主视图的观察方向；确定主视图的观察方向；

(( 使其主要表面平行或垂直于投影面使其主要表面平行或垂直于投影面 ,, 能表达更多的结构形状能表达更多的结构形状 )) 33)Draw the datum line, noticing that each view is in proper distance.)Draw the datum line, noticing that each view is in proper distance. 布置各视图的位置；布置各视图的位置；44) Project the object from three different directions and draw ) Project the object from three different directions and draw the corresponding views. the corresponding views. 按照三等规律画其三视图；按照三等规律画其三视图；

55) Check and correct , erase all unnecessary lines. ) Check and correct , erase all unnecessary lines. 校核有无错漏，擦去多余线条；校核有无错漏，擦去多余线条； 66) Draw deeply according to the demand.) Draw deeply according to the demand. 按标准图线加深视图。按标准图线加深视图。

(( 画出基准线、对称中心线、轴线）画出基准线、对称中心线、轴线）

(( 加深顺序为：圆形、圆弧、水平线、垂直线、斜加深顺序为：圆形、圆弧、水平线、垂直线、斜线线 ))

(( 可见轮廓线画粗实线，不可见轮廓线画虚线可见轮廓线画粗实线，不可见轮廓线画虚线 )) 主

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Three-View of Component Three-View of Component 物体的三视图物体的三视图3. 3. Steps for producing three-view drawings.Steps for producing three-view drawings. 画物体三视图步骤画物体三视图步骤

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俯

左

主

左 视图 L 主 (前 )视 图 F

俯 (顶 )视 图 P

Plan or top viewview

Front viewFront view

Left viewLeft view

1.Draw three views according to pictorial drawingDraw three views according to pictorial drawing.. 根据立体图画出主、俯、左三个视图。根据立体图画出主、俯、左三个视图。

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。

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Exercises 练习题练习题1. Find out the right three views for each pictorial 1. Find out the right three views for each pictorial drawing, and make out the right number in bracket.drawing, and make out the right number in bracket.找出与立体图相对应的三视图，并在括号内填写相应编号。。

2. 2. Draw three views according to pictorial drawing ( the Draw three views according to pictorial drawing ( the front view is looked from front view is looked from S)S)..

根据立体图 (( 所给主视图观察方向所给主视图观察方向 SS)) ，，画出相应的三视图。画出相应的三视图。

3. 3. Draw three views according to pictorial drawing ( the Draw three views according to pictorial drawing ( the front view is looked from front view is looked from S)S)..根据立体图(所给主视图观察方向S)，画出相应的三视图。。

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本 小 节 结 束

谢谢您的认真学习！谢谢您的认真学习！退出退出前一页前一页

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a b c

SS（（ Sight or centerSight or center

of projectionof projection投射中心投射中心））

A

B

C

Central projectionCentral projection ： ： When the lines of projection meet at a point, When the lines of projection meet at a point, it is called central projection.it is called central projection. 中心投影法中心投影法 :: 投射线汇交于一点的投影法称为中心投影法投射线汇交于一点的投影法称为中心投影法。。

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Central projection methodCentral projection method 中心投影法中心投影法

Projection linesProjection lines （（投射线投射线））

ObjectObject (( 物体物体 ) )

PP Projection planeProjection plane ( ( 投影面投影面 ))

ProjectionProjection(( 投影投影 ))

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Lines of projection will be parallel Lines of projection will be parallel (( 投射线平行投射线平行 ))

a b c

A

B

C

空间物体用大空间物体用大写字母表示写字母表示。。

投 影 用 小 写投 影 用 小 写字母表示。字母表示。

Parallel projection: When the lines of projection are parallel withParallel projection: When the lines of projection are parallel with each other, it is called parallel projection.each other, it is called parallel projection. 平行投影法 投射线互相平行的投影法称为平行投影法。平行投影法 投射线互相平行的投影法称为平行投影法。

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Parallel projection methodParallel projection method 平行投影法平行投影法

ObjectObject (( 物体物体 ) )

PP Projection planeProjection plane ( ( 投影面投影面 ))

ProjectionProjection(( 投影投影 ))

SS

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(( 一般作为辅助图样一般作为辅助图样 ) )

Axonometric projectionAxonometric projection 轴测图

Parallel Projection methodParallel Projection method 平行投影法平行投影法

(( 光线光线 SSPP 投影面投影面 )) Oblique projection methodOblique projection method

斜投影法斜投影法

Orthogonal projectionOrthogonal projection正投影图

(( 作为正式的工程图样作为正式的工程图样 ))

Orthographic projection methodOrthographic projection method 正投影法正投影法

(( 光线光线 SSPP 投影面投影面 ))

p

s s

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90° 90°

SS

SS

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Orthogonal projection Orthogonal projection 正投影图正投影图正投影图准确正投影图准确 ,, 真实真实 ,, 作作图图简单简单 ,, 但立体感不强。但立体感不强。

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Axonometric projection Axonometric projection 轴测图轴测图轴测图轴测图立体感强立体感强 ,,但但作图较作图较复杂复杂

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Priority of coinciding lines Priority of coinciding lines 图线重合时的优先顺序图线重合时的优先顺序图线有重合时的优先顺序为：图线有重合时的优先顺序为：粗实线、虚线、细点画线、双点画线、细实线。粗实线、虚线、细点画线、双点画线、细实线。

19 1. Find out the right three views for each pictorial drawing, 1. Find out the right three views for each pictorial drawing, and make out the right number in each bracket.and make out the right number in each bracket. 找出与立体图相对应的三视 图，并在括号内填写相应编号。找出与立体图相对应的三视 图，并在括号内填写相应编号。

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2

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2. Draw three views according to pictorial drawing ( the Draw three views according to pictorial drawing ( the front view is looked from front view is looked from S)S).. 根据立体图 根据立体图 (( 所给主视图观察方向所给主视图观察方向 SS)) ，，画出相应的三视图。画出相应的三视图。

S

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3. Draw three views according to pictorial drawing ( the Draw three views according to pictorial drawing ( the front view is looked from front view is looked from S)S).. 根据立体图根据立体图 (( 所给主视图观察方向所给主视图观察方向 SS)) ，，画出相应的三视图。画出相应的三视图。

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S

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在图片上点击鼠标左键可以“暂停”或再次“播放”在图片上点击鼠标左键可以“暂停”或再次“播放”

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在图片上点击鼠标左键可以“暂停”或再次“播放”在图片上点击鼠标左键可以“暂停”或再次“播放”

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在图片上点击鼠标左键可以“暂停”或再次“播放”在图片上点击鼠标左键可以“暂停”或再次“播放”

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在图片上点击鼠标左键可以“暂停”或再次“播放”在图片上点击鼠标左键可以“暂停”或再次“播放”