Engineering Graphics
Classroom Demonstration Materials:
3D Modeling (AutoCAD, Inventor and SolidWorks),
Orthographic Views and
Descriptive Geometry
This page displays some examples of engineering graphics techniques with AutoCAD, orthographic views, and descriptive geometry (sheet-metal layout and development), including hints usually not mentioned in standard drafting textbooks, and examples of errors made by students in drafting courses (YES! This include Edward Locke himself!). 3D models created in AutoCAD are used to explain how some hints about orthographic projections work. For samples of 3D modeling and relevant hints on relevant techniques, go to the SolidWorks, Autodesk Inventor, Autodesk AutoCAD, Autodesk Mechanical Desktop, CATIA and SolidEdge pages. For the FREE online textbook on descriptive geometry and sheet-metal design, go to the hosting page.
Any question? Please email me: [email protected].
Any question? Please email me: [email protected].
2D Geometric Construction in AutoCAD
The most important thing to remember when constructing geometric shapes in AutoCAD (as well as in other CAD modelers such as Inventor, SolidWorks, CATIA, and others) is to use appropriate Object Snaps.
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Development of Plutonic Solids
According to Wikipedia, the free encyclopedia, “In Euclidean geometry, a Platonic solid is a regular, convex polyhedron with congruent faces of regular polygons and the same number of faces meeting at each vertex. Five solids meet those criteria, and each is named after its number of faces.” The examples below show the developments of the surfaces of the Five Plutonic solids. These drawings are created in AutoCAD, by first draw the basic units (pentagon, triangle, and square), and then use the Copy Tool with Multiple option and Endpoint Object Snap to duplicate the basic units and complete the development.
Orthographic Projections in AutoCAD - Useful Hints
The following rules are based on Edward Locke’s experience with engineering graphics; they may or may not be mentioned in standard textbooks on engineering graphics. If any rule is incorrect in any case, please contact Edward Locke at [email protected].
The Perfect Rectangle Rule
The orthographic projections of any point on an object across the three principal views (front, side and top) and the miter line form a perfect rectangle (Figure EG-4A).
The “Similar (But dimensionally DIFFERENT) Shapes” Rule
If any surface on an object is not parallel to any of the “Three Principal Planes” (XY, XZ or YZ Planes), then the surface is show as foreshortened (NOT true shape or TS) in the orthographic Three Principal Views, the basic shape looks similar across the adjacent views but with different dimensions (Figure EG-4B and Figure EG-4C).
The “Tue Shape (TS)” and the “Edge View (EV)”
If a surface is shown as an edge view (EV, or a straight line) in one of the Three Principal Views, and the edge view is parallel to one of the Three Principal Axes that separate this view and its adjacent view, then the surface will be shown as true shape (TS) in the adjacent view (Figure EG-4B and Figure EG-4C).
If a surface is shown as an edge view (EV, or a straight line), but the edge view is NOT parallel to one of the Three Principal Axes that separate this view and its adjacent view, then the surface will NOT be shown as true shape (TS) in the adjacent view; a first auxiliary view is needed to show the true shape (TS) view of the surface (Figure EG-4D, through Figure EG-4F).
If a surface is NOT shown as an edge view (EV, or a straight line) in any of the Three Principal views, but as a foreshortened surface across the principal views, then in order to show the true shape of the surface, a first auxiliary view is needed to create the edge view (V), and then a secondary auxiliary view is needed to create the true shape view from the edge vies shown in the first auxiliary view.
The Sharing of Dimensions Rules
The orthographic projections on the top, front and bottom views share the same width dimensions along or parallel to the X-axis, for all edge lines or distances between any pair of endpoints.
The orthographic projections on the front, side and rear views share the same height dimensions along or parallel to the Y-axis, for all edge lines or distances between any pair of endpoints.
The orthographic projections on the top and side views share the same depth dimensions along or parallel to the Z axis, for all edge lines or distances between any pair of endpoints. In multi-view orthographic drawings, 45-degree miter line is used to transfer the depth dimensions across the top and side views.
The Perfect Rectangle Rule
The orthographic projections of any point on an object across the three principal views (front, side and top) and the miter line form a perfect rectangle (Figure EG-4A).
The “Similar (But dimensionally DIFFERENT) Shapes” Rule
If any surface on an object is not parallel to any of the “Three Principal Planes” (XY, XZ or YZ Planes), then the surface is show as foreshortened (NOT true shape or TS) in the orthographic Three Principal Views, the basic shape looks similar across the adjacent views but with different dimensions (Figure EG-4B and Figure EG-4C).
The “Tue Shape (TS)” and the “Edge View (EV)”
If a surface is shown as an edge view (EV, or a straight line) in one of the Three Principal Views, and the edge view is parallel to one of the Three Principal Axes that separate this view and its adjacent view, then the surface will be shown as true shape (TS) in the adjacent view (Figure EG-4B and Figure EG-4C).
If a surface is shown as an edge view (EV, or a straight line), but the edge view is NOT parallel to one of the Three Principal Axes that separate this view and its adjacent view, then the surface will NOT be shown as true shape (TS) in the adjacent view; a first auxiliary view is needed to show the true shape (TS) view of the surface (Figure EG-4D, through Figure EG-4F).
If a surface is NOT shown as an edge view (EV, or a straight line) in any of the Three Principal views, but as a foreshortened surface across the principal views, then in order to show the true shape of the surface, a first auxiliary view is needed to create the edge view (V), and then a secondary auxiliary view is needed to create the true shape view from the edge vies shown in the first auxiliary view.
The Sharing of Dimensions Rules
The orthographic projections on the top, front and bottom views share the same width dimensions along or parallel to the X-axis, for all edge lines or distances between any pair of endpoints.
The orthographic projections on the front, side and rear views share the same height dimensions along or parallel to the Y-axis, for all edge lines or distances between any pair of endpoints.
The orthographic projections on the top and side views share the same depth dimensions along or parallel to the Z axis, for all edge lines or distances between any pair of endpoints. In multi-view orthographic drawings, 45-degree miter line is used to transfer the depth dimensions across the top and side views.
Figure EG-10. The above four examples show how the above-mentioned “Sharing of Dimensions Rules” work; as shown by the light blue guidelines, the top and front views share the same width dimensions (along or parallel to the X-axis), the front and side views share the same height dimensions (along or parallel to the Y-axis), and although not shown, the top and side views share the same depth dimensions (along or parallel to the Z-axis).
Using the Sharing of Dimensions Rules to Facilitate Orthographic View Assignments
The above-mentioned “Sharing of Dimensions Rule” can be used to facilitate orthographic multiple view exercises in engineering drawing courses. The Line, Extension Line, Offset, Trim tools in AutoCAD could be used to accomplish this, as shown in the following case. In the real-world of engineering design, parametric 3D modelers such as Autodesk Inventor, CATIA, SolidWorks, Pro-Engineer, and SolidEdge are preferred due to ease of editing, interactivity, automatic generation of 2D working drawings directly from 3D models, and others. However, AutoCAD is by far the best program to learn orthographic, oblique and isometric projections and to practice related exercises. Also, due to the fact that parametric 3D modelers can automatically generate isometric and perspective views, but not oblique views, thus, AutoCAD tools could be used instead to create oblique drawings for plates, furniture and other applications.
The basic width (along or parallel to the X-axis), height (along or parallel to the Y-axis), and depth (along or parallel to the Z-axis) dimensions of the part are established across all three principal views (top, front and right side), by turning the ORTHO on to keep lines horizontal or vertical, creating a vertical line across the top and front views, a horizontal line across the front and right side views, then a horizontal line on the top view, and a vertical line on the right side view, with the Extension Line (or Line) tool; and next, by using the Offset or Copy tool with Multiple option to establish edge lines or their end points across all three views.
Hidden Lines
Hidden lines are used in orthographic views to indicate edges on the objects that are not visible in any particular view. Please not that generally speaking, hidden lines are used in orthographic multiple view working drawings only; and generally speaking they should not be drawn on presentation drawings (isometric, dimetric, trimetric views, or in oblique or perspective views).
Sectional Views
There are five types of sectional views:
1. Full section: If the imaginary cutting plane passes through the entire object, splitting the drawn object in two with the interior of the object revealed, this is called a "full section." A full section is the most widely-used sectional view.
2. Half section: The cutting plane is assumed to bend at a right angle and cuts through only half of the object, not the full length. A half section view is used only on symmetrical parts, to show a part’s internal and external structure in the same drawing.
3. Offset section: An offset section has a cutting plane that bent at one or more 90-degree angles to pass through several important features that cannot be sectioned using a straight cutting plane, for a complex part, revealing the desired features.
4. Revolving section: A “revolving section” is used for elongated objects or the elongated section of an object, using cross-sectional shape of ribs, spokes, and other projections of the object, which are “revolved.” The cutting plane cuts the object at an angle, but the drawing is rotated for a more convenient view.
5. Broken section (also called “part section” or “part sectional view”): When only a specific small part of the object (such as a screw hole), NOT the whole object, needs a section, the cutting plane is not used; instead An irregular cut line removes a section of the object at the desired depth, leaving a “broken section.”
Full, half and broken sections are the most commonly used; and samples of these types are available at http://metal.brightcookie.com/2_draw/draw_t6/htm/draw6_2_4.htm.
Figure EG-16 below shows an example of an offset section.
For more details on section views, go to http://edengdrawing.blogspot.com/2013/02/sectional-views.html.
For a reference on drawing sections in AutoCAD, go to http://www.unm.edu/~bgreen/autocad/AutoCAD%205.pdf.
1. Full section: If the imaginary cutting plane passes through the entire object, splitting the drawn object in two with the interior of the object revealed, this is called a "full section." A full section is the most widely-used sectional view.
2. Half section: The cutting plane is assumed to bend at a right angle and cuts through only half of the object, not the full length. A half section view is used only on symmetrical parts, to show a part’s internal and external structure in the same drawing.
3. Offset section: An offset section has a cutting plane that bent at one or more 90-degree angles to pass through several important features that cannot be sectioned using a straight cutting plane, for a complex part, revealing the desired features.
4. Revolving section: A “revolving section” is used for elongated objects or the elongated section of an object, using cross-sectional shape of ribs, spokes, and other projections of the object, which are “revolved.” The cutting plane cuts the object at an angle, but the drawing is rotated for a more convenient view.
5. Broken section (also called “part section” or “part sectional view”): When only a specific small part of the object (such as a screw hole), NOT the whole object, needs a section, the cutting plane is not used; instead An irregular cut line removes a section of the object at the desired depth, leaving a “broken section.”
Full, half and broken sections are the most commonly used; and samples of these types are available at http://metal.brightcookie.com/2_draw/draw_t6/htm/draw6_2_4.htm.
Figure EG-16 below shows an example of an offset section.
For more details on section views, go to http://edengdrawing.blogspot.com/2013/02/sectional-views.html.
For a reference on drawing sections in AutoCAD, go to http://www.unm.edu/~bgreen/autocad/AutoCAD%205.pdf.
Figure EG-17. Mistakes made by former students in engineering graphics course. As shown on the left, the curve marking the intersection between two cylindrical holes have been drawn as straight lines (enclosed by the red circles), which is a big mistake; As shown in the middle, light blue construction line are used to show that the intersections between the two cylinders looks like halves of ellipses, which are established by sets of four points (1, 2, 3, 4, and 5, 6, 7, 8). The correct drawing is shown on the right.
Descriptive Geometry and Sheet-Metal Development in AutoCAD
Figure EG-18A. 3D model of a cone and a cylinder intersecting at right angle, created in AutoCAD. As shown on the 3D model, the curves that define the intersection between the two objects are different on the top, front and side views, and they are neither circular nor elliptical. As sown in the Figure EG-18B and Figure EG-18C below, the intersections of the two objects as well as the development of the intersected cylindrical parts are both drawn using the principles of orthographic projections.
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Notice:
With the 3D parametric modeling programs such as Autodesk Inventor, SolidWorks and SolidEdge, the intersection of two or more objects can be automatically defines and the development of any intersected part could be created from the 3D folded model; and the relevant techniques are explored in the Learning Module Inventor 3A - Intersection and Development of Sheet-metal Parts in Inventor of my FREE online textbook. |
Figure EG-18B. The intersections between the cylinder and the cone on the Front view are drawn by the following procedure: (1) from the Right view, use the Divide tool to divide the circular edge of the cylinder into 12 parts; (2) from the division points on the circle, draw horizontal projection lines into the Front view, with the help of Node Object Snap; (3) on the Right view, from the tip of the cone, draw radiating lines passing through the division points to intersect the horizontal bottom edge of the cone; (4) from the points of intersection at the horizontal bottom edge of the cone, draw vertical projection lines upwards to intersect at the Miter Line; (5) from the points of intersection on the Miter Line, draw horizontal projection lines into the Top views to intersect at the circular edge of the base of the cone; (6) from the points of intersection at the circular edge of the base of the cone (only the bottom part is needed) on the Top view, draw vertical projection lines downwards into the Front view to intersect at the horizontal bottom edge of the cone; (7) on the Front view, from the points of intersection at the horizontal bottom edge of the cone, draw radiating lines converging at the tip of the cone, to intersect the horizontal projection line drawn at step 2; (8) on the Front view, find the corresponding points of intersection, and use the Spline tool to create the line of intersection between the cylinder and the cone on the right side; finally, use the Mirror tool to create the line of intersection on the left side; the lines of intersection between the cone and the cylinder is thus created. The intersections between the cylinder and the cone on the Top view are next drawn by the following procedure: (9) on the Top view, from the points of intersection at the circular edge of the base of the cone drawn in step 5, draw radiating lines converging at the tip of the cone (the center point of the “big circle” on the Top view); (10) on the Front view, from the points of intersection used to create the line of intersection between the cylinder and the cone (on the right side), draw vertical projection line upwards into the Top view (and the Development view as well); these lines intersect the radiating lines on the cone on the Top view; (11) on the Top view, find the corresponding points of intersection and use the Spline tool to create the line of intersection between the cone and the cylinder on the right side on the Top view; (12) use the Mirror tool to create the left side line of intersection on the Top view. Finally, the Development view of the two intersected parts of the cylinder are drawn by the following procedure: (13) on the Development view, draw a horizontal line, use the Offset tool to duplicate this line at a distance that equals the circumference of the circular edge of the cylinder; (14) on the Front view, from the right edge of the cylinder, draw a vertical projection line upward into the Development view; use the Trim tool to remove the unneeded segments so that only the portion between the two horizontal lines drawn in step 13 remains; this segment of the vertical line represent the circumference edge of the cylinder; (15) on the Development view, use the Divide tool to divide the circumference edge of the cylinder into 12 parts; (16) with the help of Node Object Snap, use the Line and Copy tools to draw horizontal projection lines to intersect the vertical projection lines created in step 10; (17) find the corresponding points of intersection and use the Spline tool to create the curved edge of the development of the right side: (17) use the Mirror tool to create the development of the intersected cylinder on the left side; (18) use the Circle tool to create the covers of the intersected cylinders on both left and right sides. When using the Line or Extension Line tool to create horizontal and vertical lines, it is advised to turn ORTHO on.
Relationship between Orthographic Multiple Views and Architectural Drawings
Orthographic multiple views used in mechanical engineering and product design drawings and Architectural Drawings are all based on the theory of orthographic projections. Their corresponding relationships could be illustrated in the table below.
Relationships among Axonometric, Oblique and Perspective Views (one-point and two-points)
Axonometric Views:
According to Wikipedia, the free encyclopedia, “Axonometric projection is a type of parallel projection used to create a pictorial drawing of an object, where the object is rotated along one or more of its axes relative to the plane of projection. There are three main types of axonometric projection: isometric, dimetric, and trimetric projection. ‘Axonometric’ means ‘to measure along axes’. Axonometric projection shows an image of an object as viewed from a skew direction in order to reveal more than one side in the same picture. […]Typically in axonometric drawing, one axis of space is shown as the vertical.
Isometric projection: “the most commonly used form of axonometric projection in engineering drawing, the direction of viewing is such that the three axes of space appear equally foreshortened, and there is a common angle of 60° between them. As the distortion caused by foreshortening is uniform the proportionality of all sides and lengths are preserved, and the axes share a common scale. This enables measurements to be read or taken directly from the drawing.”
Dimetric projection: “the direction of viewing is such that two of the three axes of space appear equally foreshortened, of which the attendant scale and angles of presentation are determined according to the angle of viewing; the scale of the third direction (vertical) is determined separately.”
Trimetric projection: “the direction of viewing is such that all of the three axes of space appear unequally foreshortened. The scale along each of the three axes and the angles among them are determined separately as dictated by the angle of viewing. Trimetric perspective is seldom used, and is found in only a few video games (Fallout, SimCity).”
“Approximations are common in dimetric and trimetric drawings.”
Oblique projection:
According to Wikipedia, the free encyclopedia, “Oblique projection is a simple type of technical drawing of graphical projection used for producing pictorial, two-dimensional images of three-dimensional objects. […] In an oblique pictorial drawing, the angles displayed among the axes, as well as the foreshortening factors (scale) are arbitrary. More precisely, any given set of three coplanar segments originating from the same point may be construed as forming some oblique perspective of three sides of a cube.” There are two major types of oblique drawing:
Cavalier projection: “The length along the axis remains unscaled.”
Cabinet projection: “Popular in furniture illustrations, is an example of such a technique, wherein the receding axis is scaled to half-size (sometimes instead two thirds the original).”
Oblique projection is completely “artificial” and the views it generates do NOT exist in the real world of optical reality. Oblique views are needed only when the true shape of the surface of a feature needs to be shown on a 3D presentation drawing, and its application is mainly in the illustrations of furniture or plates. Since most of engineering design software programs cannot generate oblique views from 3D models, learning how to create oblique views using AutoCAD 2D drafting tools is a useful skill.
Perspectives:
According to Wikipedia, the free encyclopedia, “Perspective (from Latin: perspicere to see through) in the graphic arts, such as drawing, is an approximate representation, on a flat surface (such as paper), of an image as it is seen by the eye.
The two most characteristic features of perspective are that objects are drawn:
1. Smaller as their distance from the observer increases
2. Foreshortened: the size of an object’s dimensions along the line of sight are relatively shorter than dimensions across the line of sight
[…] The most common categorizations of artificial perspective are one-, two- and three-point. The names of these categories refer to the number of vanishing points in the perspective drawing.”
1. One-point perspective: “It contains only one vanishing point on the horizon line. This type of perspective is typically used for images of roads, railway tracks, hallways, or buildings viewed so that the front is directly facing the viewer. Any objects that are made up of lines either directly parallel with the viewer's line of sight or directly perpendicular (the railroad slats) can be represented with one-point perspective. These parallel lines converge at the vanishing point.”
2. Two-point perspective: “It contains two vanishing points on the horizon line. In an illustration, these vanishing points can be placed arbitrarily along the horizon. Two-point perspective can be used to draw the same objects as one-point perspective, rotated: looking at the corner of a house, or looking at two forked roads shrink into the distance, for example. One point represents one set of parallel lines, the other point represents the other. Looking at a house from the corner, one wall would recede towards one vanishing point, the other wall would recede towards the opposite vanishing point.” […] Two-point perspective has one set of lines parallel to the picture plane and two sets oblique to it. Parallel lines oblique to the picture plane converge to a vanishing point, which means that this set-up will require two vanishing points.”
3. Three-Point Perspective: “Three-point perspective is usually used for buildings seen from above (or below). In addition to the two vanishing points from before, one for each wall, there is now one for how those walls recede into the ground. This third vanishing point will be below the ground. Looking up at a tall building is another common example of the third vanishing point. This time the third vanishing point is high in space.”
According to Wikipedia, the free encyclopedia, “Axonometric projection is a type of parallel projection used to create a pictorial drawing of an object, where the object is rotated along one or more of its axes relative to the plane of projection. There are three main types of axonometric projection: isometric, dimetric, and trimetric projection. ‘Axonometric’ means ‘to measure along axes’. Axonometric projection shows an image of an object as viewed from a skew direction in order to reveal more than one side in the same picture. […]Typically in axonometric drawing, one axis of space is shown as the vertical.
Isometric projection: “the most commonly used form of axonometric projection in engineering drawing, the direction of viewing is such that the three axes of space appear equally foreshortened, and there is a common angle of 60° between them. As the distortion caused by foreshortening is uniform the proportionality of all sides and lengths are preserved, and the axes share a common scale. This enables measurements to be read or taken directly from the drawing.”
Dimetric projection: “the direction of viewing is such that two of the three axes of space appear equally foreshortened, of which the attendant scale and angles of presentation are determined according to the angle of viewing; the scale of the third direction (vertical) is determined separately.”
Trimetric projection: “the direction of viewing is such that all of the three axes of space appear unequally foreshortened. The scale along each of the three axes and the angles among them are determined separately as dictated by the angle of viewing. Trimetric perspective is seldom used, and is found in only a few video games (Fallout, SimCity).”
“Approximations are common in dimetric and trimetric drawings.”
Oblique projection:
According to Wikipedia, the free encyclopedia, “Oblique projection is a simple type of technical drawing of graphical projection used for producing pictorial, two-dimensional images of three-dimensional objects. […] In an oblique pictorial drawing, the angles displayed among the axes, as well as the foreshortening factors (scale) are arbitrary. More precisely, any given set of three coplanar segments originating from the same point may be construed as forming some oblique perspective of three sides of a cube.” There are two major types of oblique drawing:
Cavalier projection: “The length along the axis remains unscaled.”
Cabinet projection: “Popular in furniture illustrations, is an example of such a technique, wherein the receding axis is scaled to half-size (sometimes instead two thirds the original).”
Oblique projection is completely “artificial” and the views it generates do NOT exist in the real world of optical reality. Oblique views are needed only when the true shape of the surface of a feature needs to be shown on a 3D presentation drawing, and its application is mainly in the illustrations of furniture or plates. Since most of engineering design software programs cannot generate oblique views from 3D models, learning how to create oblique views using AutoCAD 2D drafting tools is a useful skill.
Perspectives:
According to Wikipedia, the free encyclopedia, “Perspective (from Latin: perspicere to see through) in the graphic arts, such as drawing, is an approximate representation, on a flat surface (such as paper), of an image as it is seen by the eye.
The two most characteristic features of perspective are that objects are drawn:
1. Smaller as their distance from the observer increases
2. Foreshortened: the size of an object’s dimensions along the line of sight are relatively shorter than dimensions across the line of sight
[…] The most common categorizations of artificial perspective are one-, two- and three-point. The names of these categories refer to the number of vanishing points in the perspective drawing.”
1. One-point perspective: “It contains only one vanishing point on the horizon line. This type of perspective is typically used for images of roads, railway tracks, hallways, or buildings viewed so that the front is directly facing the viewer. Any objects that are made up of lines either directly parallel with the viewer's line of sight or directly perpendicular (the railroad slats) can be represented with one-point perspective. These parallel lines converge at the vanishing point.”
2. Two-point perspective: “It contains two vanishing points on the horizon line. In an illustration, these vanishing points can be placed arbitrarily along the horizon. Two-point perspective can be used to draw the same objects as one-point perspective, rotated: looking at the corner of a house, or looking at two forked roads shrink into the distance, for example. One point represents one set of parallel lines, the other point represents the other. Looking at a house from the corner, one wall would recede towards one vanishing point, the other wall would recede towards the opposite vanishing point.” […] Two-point perspective has one set of lines parallel to the picture plane and two sets oblique to it. Parallel lines oblique to the picture plane converge to a vanishing point, which means that this set-up will require two vanishing points.”
3. Three-Point Perspective: “Three-point perspective is usually used for buildings seen from above (or below). In addition to the two vanishing points from before, one for each wall, there is now one for how those walls recede into the ground. This third vanishing point will be below the ground. Looking up at a tall building is another common example of the third vanishing point. This time the third vanishing point is high in space.”
Axonometric and Two-Point Perspective:
The similarities and differences between these two views, for a cube, are explained in the table below:
The similarities and differences between these two views, for a cube, are explained in the table below:
Oblique and One-Point Perspective:
The similarities and differences between these two views, for a cube, are explained in the table below:
The similarities and differences between these two views, for a cube, are explained in the table below:
Isometric Views and Circles
To create isometric views in AutoCAD 2D drawing environment, first change to Isometric setting, and turn the ORTHO option On.
To draw any edge line that is along or parallel to any of the Three Principal Axes (X-Axis, Y-Axis and Z-Axis), draw it at full scale.
To draw any edge line that is NOT along or parallel to any of the Three Principal Axes, first find the distances between the end points of the line and the relevant Principal Axes or any edge line that is along or parallel to the relevant Principal Axes, and then use the Line tool to connect the endpoints and create the edge line.
To draw any curved line, the following steps are needed: (1) temporary switch to orthographic settings to create a “reference sketch” for the curved line; create the curved line in orthographic view starting at the Origin, draw horizontal and vertical construction line which intersect the curved line; use the Dimension tool to find the distance between all points of intersection of the curved line and the X- and Y-Axes; (2) switch back to the isometric settings; create a new layer for construction lines; and use the Line tool to create construction lines starting at the X-Axis or Y-Axis and ending at the points of intersection on the curve; return to the default isometric drawing layer; with the help of the Endpoint Object Snap, use the Spline tool to create the curve linking all points of intersection; (3) turn off the visibility of the construction line layer.
True shape might appear occasionally in Isometric if the shape is placed on an oblique plane as shown in Figure EG-13G. However, for all practical purposes, there is no true shape in isometric as shall be explained in Figure EG-13A. and Figure EG-13E. If true shapes are needed, use oblique or one-point perspective instead.
All parametric 3D modelers such as SolidWorks, SolidEdge, CATIA, and Inventor can create isometric view straight from 3D model. However, learning how to create isometric views by hand or in AutoCAD is a useful skill for engineering design, especially in the design concept ideation stage.
Most of the 3D modelers cannot create oblique view from 3D model. Therefore, learning how to create oblique views by hand or in AutoCAD is a useful skill.
Most of 3D modelers such as SolidWorks and Inventor can create perspective views straight from 3D model. Learning how to create perspective views is a tedious work that normally requires a 3-unit course (for the semester system), usually offered at the art or architecture department. Usually, perspectives views are used in graphic arts, and architectural and interior design presentations. They are rarely used in mechanical engineering design. Do NOT try to create perspective views in AutoCAD 2D drawing environment.
To draw any edge line that is along or parallel to any of the Three Principal Axes (X-Axis, Y-Axis and Z-Axis), draw it at full scale.
To draw any edge line that is NOT along or parallel to any of the Three Principal Axes, first find the distances between the end points of the line and the relevant Principal Axes or any edge line that is along or parallel to the relevant Principal Axes, and then use the Line tool to connect the endpoints and create the edge line.
To draw any curved line, the following steps are needed: (1) temporary switch to orthographic settings to create a “reference sketch” for the curved line; create the curved line in orthographic view starting at the Origin, draw horizontal and vertical construction line which intersect the curved line; use the Dimension tool to find the distance between all points of intersection of the curved line and the X- and Y-Axes; (2) switch back to the isometric settings; create a new layer for construction lines; and use the Line tool to create construction lines starting at the X-Axis or Y-Axis and ending at the points of intersection on the curve; return to the default isometric drawing layer; with the help of the Endpoint Object Snap, use the Spline tool to create the curve linking all points of intersection; (3) turn off the visibility of the construction line layer.
True shape might appear occasionally in Isometric if the shape is placed on an oblique plane as shown in Figure EG-13G. However, for all practical purposes, there is no true shape in isometric as shall be explained in Figure EG-13A. and Figure EG-13E. If true shapes are needed, use oblique or one-point perspective instead.
All parametric 3D modelers such as SolidWorks, SolidEdge, CATIA, and Inventor can create isometric view straight from 3D model. However, learning how to create isometric views by hand or in AutoCAD is a useful skill for engineering design, especially in the design concept ideation stage.
Most of the 3D modelers cannot create oblique view from 3D model. Therefore, learning how to create oblique views by hand or in AutoCAD is a useful skill.
Most of 3D modelers such as SolidWorks and Inventor can create perspective views straight from 3D model. Learning how to create perspective views is a tedious work that normally requires a 3-unit course (for the semester system), usually offered at the art or architecture department. Usually, perspectives views are used in graphic arts, and architectural and interior design presentations. They are rarely used in mechanical engineering design. Do NOT try to create perspective views in AutoCAD 2D drawing environment.
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