Difference between 2D & 3D Drawings
TWO-DIMENSIONAL (2D) DRAWINGS
The abbreviation for two-dimensional drawing is 2-D, and it describes a view having only width and height, width and length, or height and length dimensions. Two-dimensional drawings are the established design and drafting format and are common in all engineering and architectural industries and related disciplines.
The figure shows a drawing with two 2-D views representing the geometry of an aircraft part. The two views together provide width, height, and length dimensions. Views appear in ﬂat form and are normally rotated 90 degree from each other. A complete 2-D drawing typically includes dimensions, notes, and text that describes view features and details.
Two-dimensional drawings are the conventional and often required method of communicating a project. An effective 2-D drawing accurately describes design intent and product requirements, including the size, shape, and characteristics of all features, and materials, ﬁnishes, and manufacturing or construction methods. A 2-D drawing also typically documents additional project information, such as the individuals and companies involved with the project, relevant dates, approvals, and design revision history. Two-dimensional drawings can also provide computer numerical control (CNC) machine code. However, compared to 3-D surface and solid models, 2-D draw-ings offer fewer options for presenting and visualizing ideas and limited ability to analyze and test product design. In addition, 2-D drawings can sometimes be difﬁ cult to understand, especially if the reader is unfamiliar with interpreting 2-D drawings.
THREE-DIMENSIONAL (3D) DRAWINGS
The abbreviation for three-dimensional is 3-D, and it describes an object having a width, height, and depth dimensions. A wire-frame model is the most basic 3-D CAD model, and it contains only information about object edges and vertices. The word vertices are plural for vertex, which is the point where edges intersect. The term wireframe describes the appearance of the model as if constructed from wires.
Three-dimensional surface and solid modeling have replaced wireframe modeling in the CAD industry. Wireframe models have limited use as models because they lack surfaces and mass. Without surfaces, wireframe models are difﬁcult to visualize, create uncertainty about design intent, do not provide a true representation of a product, and lack volume. Some software offers the ability to hide or change the format of the lines that fall behind object features to improve visualization and as a way to create a 3-D representation, or pictorial, view for a 2-D drawing. However, the display can still cause confusion, especially when viewing complex objects. Without volume or mass, wireframe models offer limited ability to analyze and test products.
A wireframe model does offer small ﬁle size and fast display regeneration because of the ﬁle only store edge and vertex data. Wireframe models can also serve as a basis for constructing 3-D surface and solid models, and they can provide the geometry for 2-D drawings. By rotating and repurposing a wireframe model, it is possible to produce the 2-D views shown in Figure. Wireframe models can also provide 3-D CNC machine code.
THREE-DIMENSIONAL (3D) SURFACE MODELS
A surface model contains information about object edges, vertices, and surfaces (see Figure). A surface is an outer boundary of an object that connects to edges and vertices. Surfaces can display color, shading, reﬂection, and texture that signiﬁcantly improves visualization. Surfaces reduce uncertainty about design intent and provide a true representation of a product. Surface modeling also offers the ability to create complex curves and forms. The figure shows an example of a surface model with photorealistic surfaces and complex forms.
Three-dimensional surface modeling is common in the CAD industry, particularly for industrial and conceptual design and to construct certain shapes. A surface model has zero thickness, lacks mass, and may not enclose a volume. Surface models allow for basic calculations such as surface area and volume, but without mass, they offer limited ability to analyze and test physical and inertial properties. As a result, the most common users of surface models are designers who are primarily concerned with the external shape and appearance of a product. Boat and ship hull design is a common application for surface modeling. An automobile body panel is another example of a product that requires accurate surfaces. Animations, video games, virtual reality programs, and programs with similar requirements often use surface models because of the ability to form complex surfaces, especially when solids are unnecessary and ﬁle size is generally smaller than solid model ﬁles.
Surface models can serve as a basis for constructing 3-D solid models, and they can provide the geometry for 2-D drawings. By rotating and repurposing a surface model, it is possible to produce the 2-D views and display realistic surfaces on the 3-D representation, or pictorial, views. Surface models can also provide 3-D CNC machine code.
THREE-DIMENSIONAL (3D) SOLID MODELS
3A solid model is the most complex CAD format, and it contains information about object edges, vertices, surfaces, and mass. An accurate solid model is an exact digital representation of a product. Like surface models, solid models can display surface color, shading, reﬂection, and texture for presentation and visualization. The figure shows an example of a photorealistic solid model. Solid models also offer the ability to create intricate curves and forms. However, some designs require surface modeling in order to produce the desired form for a solid model. Some solid modeling software includes surface modeling tools to help model complex shapes that only surface modeling can produce or create efﬁciently.
Solid models are the most common 3-D CAD format used in the current CAD industry. A solid model encloses a volume and has mass, which allows designers and engineers to analyze the exterior and interior object characteristics and perform interference and collision checks, mass calculations, and simulations. In contrast to a 2-D drawing that includes a note that speciﬁ es the material assigned to a product, and a 3-D surface model that displays a representation of material on surfaces, a 3-D solid model can be assigned a material that closely replicates the material used to manufacture the product. Assigning a material to a solid model allows for analyzing and testing physical and inertial properties. The result is a solid model that acts as a digital prototype of a product. Solid models can provide the geometry for 2-D drawings. By rotating and repurposing a solid model, it is possible to produce the 2-D views shown in Figure and display realistic surfaces on the 3-D representation or pictorial views. Solid models can also provide data for rapid prototyping and 3-D CNC machine code.
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