make 2d drawing 3d model autocad
Affiliate 7: An Introduction to 3D CAD
Contents
About this ChapterVirtually this Chapter
Fundamental Terms in this Chapter
Why 3D CAD?
Pictorial Views Concept
- Oblique Views
- Isometric Views
- Steps to Draw an Isometric
Isometric Cartoon-Aid Functions
- Isometric Grid
- Fixed Cursor Management
- Isometric Circles, Text and Dimensions
- 2nd Drawings to Isometrics Conversion
3D Modeling
- Working with 3D Coordinates
- Cartesian Coordinates
- Spherical Coordinates
- Cylindrical Coordinates
Steps to Draw a 3D Model
User-divers Coordinate Arrangement
Displaying Views
- View Coordinate Geometry
- Object Coordinate Geometry
- Displaying Isometric Views
- Displaying Plans and Elevations
- Displaying Perspective Views
3D Drawing-Aid Functions
- 3D Set-made Shapes
- Extruding Objects in the Linear Direction
- Extruding Objects in the Circular Direction
- Shading and Rendering
AutoCAD, MicroStation and Cadkey Terms
This affiliate describes a number of 3D drawing techniques that are commonly used by CADD professionals. You volition acquire how to extrude 3D objects from uncomplicated 2D shapes, how to take advantage of 3D ready-made objects and how to make the views look realistic.
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You will also learn how to display 3D CAD views of a model from different angles.
Although the actual working of 3D CADD varies from programme to plan, the principles described here can be applied to well-nigh programs.
| | |
| Isometric | A view of an object tilted at thirty° on both sides. |
| Oblique view | A view of an object drawn by taking parallel projections from an elevation. |
| Perspective | A view of an object showing true angles equally they would appear from a specific bespeak. |
| 3D modeling | A CADD capability that allows you to draw objects equally physical objects having length, width and elevation. |
| 3D coordinates | The mode of measurement used to specify the length, width and height of objects created by 3D modeling. |
| Viewpoint | The point from where a 3D model is viewed. |
| Linear extrusion | A 3D technique that allows you to course 2D shapes into 3D shapes along a linear path. |
| Radial extrusion | A 3D technique that allows yous to form 2D shapes into 3D shapes forth a circular path. |
Why 3D CAD?
Designers often use 3D to visualize designs and to make presentations. It helps them understand how an object will appear from dissimilar angles. Using additional rendering programs can further enhance the drawings.
Although working with 3D CADD programs is quite complex, it is worth the extra attempt to make use of them. Many users never take the fourth dimension to learn the 3D capabilities of CADD. This can be a major disadvantage considering the full potential of CADD is never explored.
The views that nosotros draw on ii-dimensional media are a 2D representation of 3D images. Nosotros create isometrics and perspectives on paper by cartoon objects equally they would appear from a specific bending and distance. The aforementioned concept is used in CADD to depict pictorial views.
At that place are two singled-out ways to describe 3D views with CADD: You can draw views using elementary 2D functions or using CADD's special 3D functions.
The 2D functions let you to depict views only like on a drawing board. You can describe a view using lines, arcs, or other second objects. This is the quickest method to draw simple isometric and oblique views. Nevertheless, a view created this way is static; just like a view created on a cartoon board. If you need to view the object from a different angle, you will have to draw it over again from scratch.
CADD provides special 3D functions that allow you to create 3D drawings that are true representations of an actual model. These drawings tin can be viewed from whatsoever angle merely like a physical model. That is why 3D CADD drawings are called 3D models.
The major stardom between a 2d drawing and a 3D model is that a 2D cartoon is divers only with ii coordinates (X and Y). A 3D model is divers with three coordinates (10, Y and Z). The Z-coordinate determines the summit of an object. To make a 3D model, you need to consider all the objects of the model in 3D space and enter the X, Y and Z coordinates for all drawing objects.
3D modeling is usually a split CADD module that has its own gear up of functions. Some manufacturers marketplace second programs and 3D programs equally separate packages while others combine them into a single program.
The 3D models fall into the post-obit categories:
When you draw a model with lines and arcs, they are called wire-frame models. These models announced to be made of wires and everything in the background is visible. This does not create a very realistic effect.
Surface models are more realistic than wire-frame models. They are created by joining 3D surfaces rather than blank lines and arcs. A 3D surface is like a piece of newspaper that tin can accept whatever dimension and can be placed at any angle to ascertain a shape. Simply like a newspaper model, you join surfaces to form a surface model. The views displayed from these models are quite realistic, because everything in the groundwork can exist subconscious.
Solid models are considered solid inside and not hollow like a surface model. They announced to be the same as a surface model but take additional properties, such every bit weight, density and center of gravity, just like that of a physical object. These models are commonly used as prototypes to study engineering designs.
Example: You can draw a 3D model as a wire-frame, a surface model or a solid. To draw a 3D model of a cube equally a wire-frame, yous demand to describe twelve lines by specifying 3D coordinates for each of its points. To draw it every bit a surface model, you need to draw all vi surfaces of the cube. Although yous run into but 3 planes of the cube in front end, it is essential to describe all the planes when cartoon a 3D model. This ensures that a realistic view is displayed when it is rotated to display a view from any angle. When drawing a solid you can also specify its material.
Important Tip:
For full general 3D drawings, wire frames and surface models are used. You starting time with a wire-frame model and then fill in spaces with 3D surfaces to make information technology more realistic.
The three axes form three imaginary planes: XY plane, XZ aeroplane and YZ plane. The XY plane is the horizontal plane and the XZ and YZ are the two vertical planes. When you need to draw something horizontal, such as the program of a building, you draw information technology in the XY plane using 10 and Y coordinates. This generates a plan view. When you need to draw something vertical, such as an elevation of a building, you draw information technology using the XZ or YZ planes.
Example: To depict a line in 3D, enter two stop points divers with 10, Y and Z coordinates. If you need to draw the line lying apartment on the footing (XY airplane), the Z coordinate for both the finish points of the line is nil. If you lot want to draw the aforementioned line at 10'-0" to a higher place the XY plane, enter the Z-coordinate for both the end points as 10'-0".
The 3D coordinates can be entered using the post-obit formats:
Cartesian coordinates are based on a rectangular system of measurement. In Chapter 2 "CADD Basics", we discussed how Cartesian coordinates are used in 2D drawings. The aforementioned principle is practical to enter 3D coordinates with the exception that you need to enter an additional Z coordinate. Positive Z-coordinate values are used when you need to measure out distances to a higher place the XY plane; negative values are used for the distances below the XY aeroplane.
Coordinate values are entered separated by commas (X,Y,Z). The coordinates tin can be measured from the origin signal (accented coordinates) or from the last reference location of the cursor (relative coordinates).
Spherical coordinates are based on the longitude and latitude system of measurement (Diagram A, Fig. 7.11). Consider the origin signal of the coordinate system at the middle of the globe or a transparent globe. And then consider a horizontal plane (XY airplane) passing through the middle of the world. To locate a bespeak in 3D, first locate a point in the XY plane by specifying a radius and an angle (polar coordinates). To specify the tiptop, enter an angle up or downwards from the XY aeroplane (latitude).
Note:
Spherical coordinates are not very efficient for drawing purposes. They are commonly used to view a model from unlike angles.
Cylindrical coordinates are usually used to describe cylindrical shapes. They are based on a cylindrical system of measurement. Consider a cylinder placed vertically and the origin point at the middle of the cylinder (Fig. 7.12, Diagram A). Cylindrical coordinates are quite like to spherical coordinates, the difference being that the Z-coordinate is specified by tiptop and not angle.
To locate a betoken with the cylindrical coordinates, first you need to locate it in the XY plane just like polar coordinates. And so signal an verbal summit at that signal.
There are 2 main protocols used to display views:
View Coordinate Geometry
View coordinate geometry assumes that the camera (viewpoint) remains stationary and the 3D model is rotated to display a desired view. The model can be rotated effectually the Ten, Y, or Z centrality. You need to specify effectually which axis the rotation volition accept identify and by how much. When you rotate the model around the Z-axis, the model rotates in the XY plane; when you rotate it around the Y-centrality, the rotation takes place in the XZ airplane.
Object Coordinate Geometry
Object coordinate geometry assumes that the model remains stationary and the photographic camera (viewpoint) is moved to a display a desired view. You can use any of the coordinate methods to specify an verbal viewpoint. Spherical coordinates are particularly helpful to indicate a viewpoint.
Comparison: View coordinate geometry tin be compared to holding a small model in your hand and rotating it on its sides to get a desired view. Object coordinate geometry can be compared to viewing a building from the sky. The edifice remains stationary, while the photographic camera is moved to become a desired view.
Note: Virtually CADD programs provide both view coordinate geometry and object coordinate geometry options to brandish views. Depending on how you lot want to view a model, yous tin use either method.
To brandish an isometric, yous need to specify the direction from which the view is to be taken. The almost appropriate method to betoken management is with the help of spherical coordinates. You lot demand to specify two angles: an bending in the XY plane (longitude) and an bending from the XY aeroplane (latitude). The longitude determines the orientation of the model in the XY plane and the latitude determines the top of the viewpoint.
Important Tips:
You lot can catechumen this model into a surface model by drawing 3D surfaces for each of the planes. You can draw a surface for the superlative of the model by indicating the points I,J,K and 50. This model requires a total of vii surfaces for all the sides: meridian, bottom, four sides and one inclined surface.
You can dispense the views of a 3D model in a number of ways. You can rotate the view, cut a section of the view along a plane, reduce or overstate the view, change the focus of the view, hibernate and brandish certain lines, etc.
You can brandish more than one view of a model on the screen at the same time. You lot can create a number of viewing windows (viewports) that tin be used to display different views. For example, you can display a programme view of the model in one viewport, summit in another and a perspective view in another. When you depict something in one viewport, it is automatically shown in all the viewports.
Avant-garde CADD programs enable yous to create animated images. You can create perspective views and store them in the estimator memory. You tin can display a number of these images within seconds to create an animated effect. You can create an effect that simulates walking through a edifice or the functioning of a machine.
Refer to CADD PRIMER for details on the topics listed above.
Note: CADD PRIMER is illustrated with more than than 100 diagrams. The above diagram is an instance from CADD PRIMER illustrating the concept of spherical coordinates used in CADD.
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Source: https://caddprimer.com/cadd_primer_chapters/isometric_perspective_3d_cad_7.htm
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