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The Goodheart-Willcox Co., Inc.Tinley Park, Illinois


Chapter 5Chapter 5

Axonometric Drawing Techniques


Learning ObjectivesLearning Objectives

Identify and explain the different types of pictorial and axonometric drawings.

Plan, lay out, and draw isometric views of objects containing normal, inclined, skewed, irregularly curved, and circular surfaces.

Use isometric ellipse templates, isometric protractors, and angle ellipse templates as drawing aids.


Learning ObjectivesLearning Objectives

Identify and explain the primary applications of computer-generated axonometric drawings.

Develop drawings using the isometric, dimetric, and trimetric methods of pictorial drawing.


Pictorial DrawingPictorial Drawing

A style used to show all three dimensions of an object in a single view.

Used in technical illustration almost exclusively.

Each pictorial style can be further divided into specific classifications.


Pictorial DrawingPictorial Drawing


Axonometric DrawingsAxonometric Drawings

There are three drawing types. Isometric

Refers to equal measure. Dimetric

Refers to two measures. Trimetric

Refers to three measures.



In an isometric drawing, equal angles (120°) are used between each of the primary axes. The scales used for each axis are also equal.

In a dimetric drawing, two of the angles used between the primary axes are equal. Two of the scales for the axes are equal.

In a trimetric drawing, the axis intersections produce three different angles. Three different scales are used for the axes.


Oblique DrawingsOblique Drawings

An oblique drawing is similar to an axonometric drawing.

A front view is parallel to the projection plane and top and side views are viewed at an oblique angle.

The width and height axes are full scale. The receding axis scale varies depending

on the type of drawing. The receding axis angle can be any angle

between 0 and 90.



There are three types. Cavalier oblique

The receding axis is full scale. Cabinet oblique

The receding axis is half scale. General oblique

The receding axis is drawn at a scale other than one-half or full size.



Common receding axis angles and scale factors are typically used.


Perspective DrawingsPerspective Drawings

Used to represent what is normally seen from a given viewing point.

Receding axis lines converge to a vanishing point as they recede.

There are three types related to the number of vanishing points. One-point perspective Two-point perspective Three-point perspective


Perspective DrawingsPerspective Drawings


Applications of Pictorial Applications of Pictorial DrawingsDrawings

Each style has advantages and limitations.

Select the most appropriate method for a given illustration.

Proper selection enhances viewer understanding and saves drawing time.


Axonometric Drawing Axonometric Drawing ApplicationsApplications

Primary use is for rectangular objects with flat plane surfaces.

Curved and irregular shapes are difficult to show because of receding object faces.

Isometric drawings are the most used. Advantages include ease of layout and scaling. Disadvantages include a slight oversizing and

distortion of proportion. Dimetric and trimetric views can produce

more realism but take longer to draw.


Oblique Drawing Oblique Drawing ApplicationsApplications

Primary use is for objects with circular, cylindrical, or irregular shapes easier to draw with a normal front view.

Also used for objects with one long axis.


Perspective Drawing Perspective Drawing ApplicationsApplications

Primary use is in architectural and interior design.

Very realistic views are used to show a specific viewing location and elevation.

More drawing time is required. Most suitable for flat-surface

objects with rectangular shapes.


Advantages of PictorialsAdvantages of Pictorials

Provide the best way to represent an object.

Simplify what is shown for the viewer. Quicker to draw than multiview drawings. Hidden lines are normally excluded. Placing part labels and notes is much

quicker than dimensioning orthographic views.


Disadvantages of PictorialsDisadvantages of Pictorials

Present difficulty when dimensions are required for manufacturing.

The viewing angle may cause distortion in the object.

Hidden details may be difficult to visualize.

Complex shapes may be difficult to draw.


Isometric ProjectionIsometric Projection

The object is rotated 45 to the frontal plane and tipped forward 35°16 from the horizontal plane.

Horizontal lines are drawn at 30 from the X axis.

In comparison to an isometric drawing, measurements are foreshortened by approximately 82%.

Foreshortening all measurements can make a true-scaled view difficult to draw.


Isometric ProjectionIsometric Projection


Isometric Drawing Isometric Drawing

An isometric drawing is made at full scale.

The object is approximately 1.22 times larger than an isometric projection.


Isometric Drawing TypesIsometric Drawing Types Regular isometric drawing

Horizontal axes are drawn at 30° (most common).

Reversed axis isometric drawing The orientation of the axes is the exact opposite

of the regular axis isometric orientation. Used to show details on the bottom of an object.

Long axis isometric drawing Includes a major horizontal axis and two axes

inclined at 60°. Used to show features along one axis.


Isometric Drawing TypesIsometric Drawing Types


Object Orientation in Object Orientation in Isometric ViewsIsometric Views

Choose the best view where the desired features are emphasized.

The object should be drawn in its operating position orientation.

Select a different view if the most natural has many hidden features.


Drawing Isometric Lines Drawing Isometric Lines and Nonisometric Linesand Nonisometric Lines

Horizontal and vertical isometric lines are always parallel to the isometric axes.

Nonisometric lines are inclined to the isometric axes. To draw, each endpoint is first plotted on

isometric lines. Plotted points are then connected.

The block-in technique is useful and accurate.


Block-in TechniqueBlock-in Technique

First, draw an isometric block with light construction lines and the overall dimensions.

“Block in” the individual points of the profile and connect the points with isometric lines until the shape is defined.

Develop all normal isometric lines first, then one nonisometric surface at a time.


Block-in TechniqueBlock-in Technique

Locate the step features on the front face first. Locate the corresponding points on the back

plane of the block. Connect the points with isometric lines.


Block-in TechniqueBlock-in Technique Nonisometric lines and surfaces require

additional steps. Draw an isometric block with the overall

dimensions. Measure distances on each orthographic

view and transfer to points on isometric lines parallel to axis lines on the block.

Connect the points with nonisometric lines. Nonisometric lines are not true length

and cannot be measured directly with a scale.


Block-in Technique Block-in Technique (Nonisometric Surfaces)(Nonisometric Surfaces)


Drawing Isometric Arcs, Drawing Isometric Arcs, Circles, and Irregular Circles, and Irregular

CurvesCurves Circles and arcs appear as ellipses

in an isometric drawing. The coordinate method simplifies

the drawing process for arcs. Points are located on curves using

isometric lines as reference lines. An orthographic view is commonly

used to transfer coordinate points.


Coordinate MethodCoordinate Method

First, “block in” the basic object shape. Identify coordinate points on the curved

shape in the orthographic projection. Transfer coordinates from the

orthographic view to the corresponding points in the isometric view.

Connect the points in a smooth curve with an irregular curve or spline.

Locate points on the closest surface first, then background features.


Coordinate MethodCoordinate Method


Constructing Isometric Constructing Isometric CirclesCircles

The four-center method is more efficient than the coordinate method. Plotting coordinates for a circle

requires many points to provide a good shape definition.

Using arcs and center points on an isometric plane simplifies the process.


Four-Center MethodFour-Center Method1. Locate the center of the isometric circle

and draw a square around it with isometric lines.

2. Locate the midpoint on each side.3. Draw lines from the corners to the

opposite midpoints.4. Draw the ellipse sides using the necessary

radii and the corners as the centers. Draw the ends using the necessary radii and the line intersections as the centers.

5. Check for smoothness before darkening.


Four-Center MethodFour-Center Method

The radius values labeled R1 are for the ellipse sides.

The radius values labeled R2 are for the ellipse ends.


Four-Center MethodFour-Center Method

If the arcs do not meet properly, draw a correction arc. Reset the compass

to the proper radius of the small arc.

Draw arcs from the ends of the large arcs to locate a new center.

Draw the arc.


Centering Isometric ViewsCentering Isometric Views

Regular isometric drawing1. Locate the center of the drawing area.2. Drop a vertical line from the center point

one-half the maximum height of the object.3. Draw a 30° line one-half the width of the

object. To show the front face on the left, draw to the right. To show the back, draw to the left.

4. Draw a 30° line one-half the depth of the object in the opposite direction of the line drawn in Step 3. The endpoint is the bottom front or bottom rear corner of the object.



Reversed axis isometric drawing1. Locate the center of the drawing area.2. Draw a vertical line up from the center point

one-half the maximum height of the object.3. Draw a 30° line one-half the width of the

object. To show the front face on the left, draw to the right. To show the back, draw to the left.

4. Draw a 30° line one-half the depth of the object in the opposite direction of the line drawn in Step 3. The endpoint is the top front or top rear corner of the object.


Centering Isometric ViewsCentering Isometric Views Long axis isometric drawing

1. Locate the center of the drawing area.2. Drop a line from the center point one-half the

width of the object at a 60° angle to horizontal. To show the front face on the left, draw to the right. To show the back, draw to the left.

3. Draw a 60° line one-half the object height in the opposite direction of the line drawn in Step 2.

4. Draw a horizontal line one-half the object depth in the same direction as the line in Step 3. The endpoint is the bottom front or rear of the object.


Isometric Drawing AidsIsometric Drawing Aids

More types of templates are available for isometric drawing than for any other type of drawing.

US Customary and metric sizes are available.

There are three major types of templates. Isometric ellipse template Angle ellipse template Isometric protractor


Isometric Ellipse Isometric Ellipse TemplatesTemplates

Made of plastic with precise holes for tracing.

Used to draw ellipses on normal isometric surfaces.

Holes are 22% oversized (no calculations are needed).

Templates are labeled Isometric or 35°16.


Angle Ellipse TemplatesAngle Ellipse Templates Used for circular shapes inclined or

skewed to the principal projection planes.

Holes are true size. Use a larger ellipse to compensate for

isometric oversizing. For US Customary sizes, multiply the true

size by 1 1/4 (1.25) and round to the closest size available.

For metric sizes, multiply the true size by 1.22 and round to the closest size available.


Angle Ellipse TemplatesAngle Ellipse Templates

Full sets normally consist of a series of 10 separate templates. Viewing angles range from 10° (very

flat) to 55° (almost circular). Templates progress in increments of 5°.

Templates are selected for different isometric surfaces with an isometric protractor.


Using Isometric Ellipse Using Isometric Ellipse TemplatesTemplates

Align the proper axis lines with construction lines on the drawing.

The ellipse must have three-axis alignment. The ellipse center is first aligned with

the center of the hole or cylinder. The ellipse is turned to align with the

vertical axis and the appropriate horizontal axis.


Using Isometric Ellipse Using Isometric Ellipse TemplatesTemplates

On vertical surfaces, the minor ellipse axis is parallel to the horizontal axis on the other side of the vertical axis and one axis line is vertical.

On horizontal surfaces, the minor axis is vertical and the major axis is horizontal.


Using Angle Ellipse Using Angle Ellipse TemplatesTemplates

Orient the ellipse center on the construction line center point on the drawing.

Rotate the ellipse so the minor axis is parallel to the centerline (thrust line) of the circular shape. Determining the angle of the ellipse and

drawing the thrust line present difficulty. An isometric protractor is typically used to

identify the angle ellipse and thrust line.


Using Angle Ellipse Using Angle Ellipse TemplatesTemplates

A 1 ellipse is used for a .8125 diameter hole (.8125 1.22 = 1.01 or 1).

The ellipse minor axis is aligned parallel to the thrust line.


Using Ellipse TemplatesUsing Ellipse Templates

Isometric ellipses can be used to measure distances along nonisometric lines and surfaces.

Any point on the ellipse perimeter represents the same distance from the center.

To measure, the ellipse must always be properly oriented on the drawing plane.


Using Ellipse TemplatesUsing Ellipse Templates

After isometric lines are drawn, a 1 isometric ellipse sets the thickness of the inclined face.

A 1/2 ellipse tangent to the top edge sets the thickness of the upper nonisometric face.


Isometric ProtractorIsometric Protractor

Used to measure nonisometric angles.

Readings are divided into four quadrants.

Angular values progress from 0 to 90 and reverse back to 0.

To use, the minor axis of the template is aligned with an appropriate isometric axis.



Elliptical shapes identify the different angle ellipses.

A line through each ellipse aligns with the minor axis and represents the thrust line.

The reading along the edge identifies the thrust line angle. Use the angle to determine the angle ellipse

required. Use the closest ellipse to the reading for

thrust lines that do not align precisely with an ellipse.


Developing Nonisometric Developing Nonisometric FeaturesFeatures

Measure the angle to draw the nonisometric line. Draw the horizontal line for the top surface and

then complete the front face.



To draw the top surface, align the protractor with the top vertex point and measure 90 to establish the line perpendicular to the front face.

Center and align the protractor on the front face and draw the thrust line parallel to a perpendicular axis line.



Calculate the thrust line angle in the proper direction by counting degrees toward the “open air” side of the object.

For the thrust line angle reading of 60, a 50 angle ellipse is used.


Isometric Drawing with Isometric Drawing with Computer-Aided Drafting Computer-Aided Drafting

(CAD)(CAD) CAD programs typically provide tools and

features that simplify isometric drawing. Isometric grid

A 30 dot pattern establishes the drawing axes.

Used for layout, blocking in, and drawing. Grid and snap spacing is set based on

divisions related to major drawing features. Isometric cursor

Provides a visual aid for axis alignment.


Isometric GridIsometric Grid


Isometric AxesIsometric Axes

In a CAD system, isometric lines are easily drawn using angle entries.

Each axis line can be drawn with one of two angles.

Angles are typically measured counterclockwise from 0 horizontal.

Isometric axis angles are useful to know when the grid is not suitable.

Other angles are used for nonisometric lines.


Isometric Axis Drawing Isometric Axis Drawing AnglesAngles


Isometric Line Drawing Isometric Line Drawing Functions in CADFunctions in CAD

Absolute and relative coordinates are used to a lesser extent in isometric drawing.

Polar coordinate entry is an essential tool. Coordinates are normally located from a

previous point using a distance and angle (e.g., @5<30).

Drawing typically begins in the lower-middle portion of the screen. The drawing is centered once complete.


Drawing Isometric LinesDrawing Isometric Lines

The left face begins with the Line command at the origin. Point 1: @3<150 Point 2: @2<90 Point 3: @1<330 Point 4: @1<270 Point 5: @2<330 Origin: @1<270 or

Close



The top-left face begins at Point 2. Point 6: @2<30 Point 7: @1<330 Point 3: @2<210



The top-right face begins at Point 5. Point 9: @2<30 Point 8: @2<150 Point 4: @2<210



To complete the upper portion of the right face, pick Point 8 and enter @1<90.

To complete the lower-right face, pick the origin and enter @2<30 (Point 10) and then @1<90 (Point 9).


Isometric PlanesIsometric Planes

The three normal isometric planes are identified with different cursors. Left isoplane Right isoplane Top isoplane

The isoplane cursors are used for regular or reversed axis isometric drawing.

A different cursor is required for long axis isometric drawing.


Isometric PlanesIsometric Planes


Isocircle and Ellipse Isocircle and Ellipse FunctionsFunctions

CAD systems typically provide tools for drawing isometric ellipses (isocircles) automatically.

To draw, select the desired isoplane, then enter the center point and radius or diameter.

Drawing procedures vary for nonisometric ellipses.


Isometric Editing and Isometric Editing and Illustrating TechniquesIllustrating Techniques

Trimming or clipping allows removal of lines for hidden features. A cutting edge is used. The Erase command is also useful.

Lines may be added or deleted to enhance visualization or save time while leaving design requirements unchanged.

Try different editing functions if those used in orthographic views are not useful.


Trimming Isometric Trimming Isometric FeaturesFeatures


Dimetric DrawingDimetric Drawing

Often used as a compromise between isometric and trimetric drawing. Isometric oversizing may be undesirable. Less time is required than in trimetric

drawing. Common axis angles and scales are

used.


Dimetric Drawing Axis Dimetric Drawing Axis Combinations (Regular Combinations (Regular

Axis)Axis)


Dimetric Drawing Axis Dimetric Drawing Axis Combinations (Reversed Combinations (Reversed

Axis)Axis)


Dimetric Drawing Dimetric Drawing PrinciplesPrinciples

Circular features may require special methods. Angle ellipse templates can be used

for features lying between axes with the same scale.

Coordinate layout is used for features lying between axes with different scales.


Coordinate Layout for Coordinate Layout for Circular Shapes (Dimetric Circular Shapes (Dimetric

Drawing)Drawing)1. Draw an orthographic view and divide

with grid lines to locate points on the perimeter.

2. Draw a grid aligned with an axis in the dimetric view. Use the appropriate scale for the grid lines along the foreshortened axis.

3. Transfer points to the dimetric view.4. Fit the points.


Coordinate Layout for Coordinate Layout for Circular Shapes (Dimetric Circular Shapes (Dimetric

Drawing)Drawing) A 10 left and 40 right axis layout is used in the example.

The scales are 1 for the left and vertical axes and .5 for the right axis.

The left face does not require coordinate layout.


Dimetric Drawing Dimetric Drawing ApplicationsApplications

Use when appearance and proportion are more important than drawing time.

Avoid when the drawing has circular or irregular shapes.

Objects with rectangular or normal surfaces are most suitable.


Trimetric DrawingTrimetric Drawing

Typically provides the most realism of the axonometric drawing styles.

Requires more time to develop and is used less than isometric and dimetric drawing.

Drawings have three different axis angles and scales.

There are two major horizontal axis angle orientations. 45/15 35/25


Trimetric Drawing Axis Trimetric Drawing Axis Angle OrientationsAngle Orientations


Trimetric Drawing Trimetric Drawing PrinciplesPrinciples

Measures along each axis can be developed using angle ellipse sizing rather than specific scales. For 45/15 axis orientations, use 25, 35,

and 55 angle ellipses for the three faces. For 35/25 axis orientations, use 30, 40,

and 35 angle ellipses. Block in the object first, then locate

features using angle ellipses or scales.


Trimetric Drawing Axis Trimetric Drawing Axis MeasurementsMeasurements



Common axis scales are used for drawings with 45/15 axis angle orientations. Vertical axis scale = 1 Scale for axis with smallest receding angle

= .75 Scale for axis with largest receding angle = .5 Circular features must be developed using

coordinate layout. Using specific scales for other

configurations can cause object distortion.



Proper object orientation is important. For objects with a much longer axis for one

side than others, rotate the view so the side aligns with the smaller receding angle.


Trimetric Drawing Trimetric Drawing ApplicationsApplications

Use when proportionate pictorial drawings are required.

If drawing time is a factor, other methods are normally used.

Objects with rectangular or normal surfaces are most suitable.


Parallelogram Parallelogram Construction of Arcs and Construction of Arcs and

CirclesCircles Sometimes required for dimetric

and trimetric drawings. Used when a surface angle cannot

be calculated or an angle ellipse protractor is not suitable.

Used for circular shapes with different scales on their axes.



CirclesCircles First, draw a parallelogram with sides parallel to the axis lines of the surface.

Locate the ellipse center (use diagonal lines if the hole is centered on the surface).

Locate the endpoints of the major axis along the longer diagonal.

Select an angle ellipse. Draw the ellipse at true scale and tangent

to the parallelogram sides.



CirclesCircles

The example uses 10 and 40 angles for the horizontal axes.

The scale factors are 1 for the left and vertical axes and .5 for the right axis.


Computer-Aided Dimetric Computer-Aided Dimetric and Trimetric Drawingand Trimetric Drawing

CAD systems provide numerous tools that simplify drawing methods.

Ellipse construction is much simpler. Several CAD aids are particularly useful.

Grid and snap rotations Modified scaling functions Editing options


Establishing Dimetric and Establishing Dimetric and Trimetric AxesTrimetric Axes

Rotate the snap and grid to angles that set the horizontal axes.

Set snap and grid distances to reflect object dimensions.

Change axis alignments depending on the features to be constructed.


Scale Modification Scale Modification FunctionsFunctions

Different methods can be used to simplify drawing based on the tools available. Enter the exact distances required by

calculating scaled measures mathematically. Set the snap to an axis scale factor and the

grid to a related value. Enter fractional values using polar

coordinates based on the axis scales needed. Use mathematical expressions with the

system calculator.


Object Snap Functions in Object Snap Functions in Dimetric and Trimetric Dimetric and Trimetric

DrawingDrawing Several object snap modes are useful.

Intersection Endpoint Midpoint Node (point) Tangent

Box in the object to set reference points. Use construction lines or points as

needed. Copy objects whenever possible.


Dimetric and Trimetric Dimetric and Trimetric Drawing Editing FunctionsDrawing Editing Functions

Several basic commands provide different ways to modify objects. Scale Copy Mirror Erase Trim and Extend

Save before and after making edits.


ScaleScale Command Command

Apply after objects are first drawn full scale.

Receding measurements can be scaled as needed.

Using system calculations helps reduce mistakes.


CopyCopy Command Command

Use for lines or arcs that are repeated in a drawing.

Make copies to avoid drawing the same object twice.

Use snap functions to maximize productivity.


MirrorMirror Command Command

Useful when a dimetric drawing has equal angles and scales for the horizontal axes.

One side can be mirrored about the vertical axis to avoid redrawing features.

Use endpoints rather than snap points or grid dots to select the mirror line.


EraseErase Command Command

Use to remove construction lines and unwanted features.

Place features to be removed on a single layer so it can be deleted.


TrimTrim and and ExtendExtend CommandsCommands

Use to modify temporary construction lines and arcs into finished objects.

Trimming removes portions of an object at a cutting edge.

Extending adds to an object so it meets a boundary edge.


QuestionsQuestions

What are the three types of axonometric drawings?

Isometric, dimetric, and trimetric. At what scale is the receding axis

drawn in a cavalier oblique drawing?Full scale.

What is the primary use for perspective drawings?

Architectural and interior design.


QuestionsQuestions

At what angle are horizontal lines drawn in a regular isometric drawing?

30° above horizontal. What types of shapes are drawn

using the four-center method?Isometric circles.


QuestionsQuestions

What is the difference between isometric and nonisometric lines?

Isometric lines are parallel to the isometric axes. Nonisometric lines are not parallel to an isometric axis.

What is the difference between holes on isometric and angle ellipse templates?

Holes on an isometric ellipse template are 22% oversized and no calculation is necessary to use them. On an angle ellipse template, holes are true size and larger ellipses must be used.


QuestionsQuestions

How are ellipses aligned on vertical isometric surfaces?

The minor ellipse axis is parallel to the horizontal axis on the other side of the vertical axis on the drawing.

What is the purpose of an isometric grid in a CAD drawing?

It establishes a 30 pattern for the isometric drawing axes.


QuestionsQuestions What type of coordinate entry is an

essential tool for pictorial drawing in a CAD system?

Polar. What CAD editing function permits the

removal of lines for hidden features and uses a cutting edge?

Trimming. What types of objects lend themselves

best to dimetric drawing?Objects with rectangular or normal surfaces.


QuestionsQuestions

What two horizontal axis angle orientations are most commonly used in trimetric drawing?

45/15 and 35/25.


GlossaryGlossary

Cabinet obliqueAn oblique drawing in which the receding axis is drawn at half scale.

Cavalier obliqueAn oblique drawing in which the receding axis is drawn at full scale.

Coordinate methodA method of defining curves on foreshortened or angled surfaces in which points on a grid are transferred from an orthographic view.


GlossaryGlossary

Dimetric drawingAn axonometric pictorial drawing in which two of the three angles created by the intersections of the axes are equal, but the third angle is different. Measurements along two of the axes use the same scale, but the third axis is drawn at a different scale.

Four-center methodA method used to locate center points for arcs defining an isometric circle.


GlossaryGlossary General oblique

An oblique drawing in which the receding axis is drawn at a scale other than one-half or full size, typically a three-quarter scale.

Isometric cursorIn a CAD system, a set of crosshairs that are rotated to align with the isometric axis.

Isometric drawingAn axonometric pictorial drawing in which the axes form 120 angles and measurements along all axes are drawn to the same scale.


GlossaryGlossary Isometric grid

In a CAD system, a series of dots that align on a 30 pattern to establish the left and right axes.

Isometric linesHorizontal and vertical lines parallel to an isometric axis.

Isometric protractorA drafting instrument used to measure angles inclined or skewed to the principal isometric planes.


GlossaryGlossary

Long axis isometric drawingAn isometric drawing that has one major axis aligned horizontally and the other axes inclined at a 60° angle to horizontal.

Nonisometric linesLines in an isometric drawing that are not parallel to one of the isometric axes.


GlossaryGlossary

Oblique drawingA type of pictorial drawing in which the front face is parallel to the projection plane, and the top and side views are viewed at an oblique angle. A receding axis is used to measure the depth and extends away from the face.

One-point perspectiveA type of pictorial drawing in which a front view is parallel to the picture plane and receding axis lines converge at a single vanishing point.


GlossaryGlossary Operating position orientation

The position an object is in when a person is using, controlling, or viewing it in its natural environment.

Regular isometric drawingA drawing in which the left and right horizontal axes are drawn at a 30° angle above horizontal.

Reversed axis isometric drawingA drawing in which the axes are drawn in the exact opposite orientation as a regular axis isometric drawing.


GlossaryGlossary

Three-point perspectiveA type of pictorial drawing in which the principal planes are inclined to the picture plane and receding axis lines converge to three vanishing points.

Trimetric drawingAn axonometric pictorial drawing in which all three angles created by the intersections of the axes are unequal, and each axis uses a different scale.


GlossaryGlossary

TrimmingIn a CAD system, removing a portion of an object using another object as a cutting edge. Also known as clipping.

Two-point perspectiveA type of pictorial drawing in which the principal planes are inclined to the picture plane and receding axis lines converge to two vanishing points.


GlossaryGlossary

Vanishing pointA point in a perspective drawing where receding lines converge.

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