Solid modelling is a computer-aided design (CAD) technique for creating three-dimensional models of objects.
Unlike surface modelling, which focuses on creating the outer shell of an object, solid modelling involves creating a complete representation of an object, including its volume and interior features. This allows for more accurate and detailed designs, making it ideal for the engineering and manufacturing industries.
Now, let’s learn more about solid modelling, its methods, and its essential components by continuing to read.
Solid modelling is a 3D computer-aided design (CAD) technique that involves constructing a digital representation of an object’s geometry by adding and subtracting volumes to create a solid model.
Objects with complex shapes, like mechanical parts, buildings, and other structures, can be designed and analysed using solid modelling. When modelling objects with curved surfaces and fine details, which are challenging to accomplish with conventional 2D drafting methods, solid modelling is especially helpful.
With this method, designers are able to visualise and manipulate objects in 3D space, making it easier to understand their shape, size, and orientation. The process of solid modelling typically involves creating a wireframe model, then adding thickness and other properties to create a solid model.
Automotive, aerospace, construction, and consumer products are several industries that use solid modelling. Their use case scenarios vary from designing to optimising products and structures for manufacture and performance.
Aside from solid modelling, design automation is an important technique to learn during the modelling process. Design automation refers to the use of software tools and technologies to automate and streamline design processes in industries such as engineering, architecture, and manufacturing.
Learn more in our previous post, “Design Automation: What It Is and How It Benefits the Construction Process”.
Solid Modelling Techniques
There are several techniques used in solid modelling, including primitive instancing, surface mesh modelling, CSG, and sweeping. These techniques allow designers to create complex shapes and structures with precision and efficiency.
Here is an explanation of each technique according to:
- Primitive Instancing: This technique is based on the notion of families of objects, each member of a family distinguishable from the other by a few parameters¹. For example, a block primitive is defined by three parameters: height (H), width (W), and depth (D).
- Spatial Occupancy Enumeration: This scheme is essentially a list of spatial cells occupied by the solid.
- Cell Decomposition: This technique involves breaking down a complex object into simpler, manageable parts.
- Surface Mesh Modelling: This method represents a solid as a mesh of interconnected surfaces.
- Constructive Solid Geometry (CSG or C-Rep): In a CSG approach, a solid model of an object is created by using three-dimensional geometric entities, known as primitives. These primitives can be combined by a mathematical set of Boolean operations to create the solid.
- Sweeping: This technique involves creating a 3D shape by moving a 2D shape along a specified path.
- Implicit Representation: This method represents a solid with an equation or a set of equations.
- Parametric and feature-based modelling: This technique uses parameters to define the features of a model, allowing for easy modification and iteration.
Each of these techniques has its own advantages and is used in different scenarios depending on the requirements of the model. For example, CSG is often used in CAD systems due to its ability to easily modify complex objects.
Solid modelling software (Image by BIM SCALER)
Solid Modelling vs. Surface Modelling: What is the Difference?
Solid modelling and surface modelling are both 3D modelling techniques used in computer-aided design (CAD) software. The main difference between the two lies in the way they represent and manipulate 3D objects.
Solid modelling is similar to a carpenter gluing and shaping pieces of wood to make a toy car, whereas surface modelling is comparable to a stained glass artist cutting out panels of glass and soldering them together at the seams to create a lampshade.
Both of these processes can be used to achieve the same result and do not exist in a binary. They can be used in tandem to construct your desired geometry.
Here are the key differences, according to Epec blog:
Solid Modelling
Solid modelling, also known as boundary representation (B-rep) modelling, represents 3D objects as watertight volumes defined by mathematically defined surfaces connected by topology. This approach is precise in terms of volume and mass and allows for accurate shape creation. However, it can be complex and time-consuming, requiring large system memory.
- Solid modelling is the process of constructing a 3D model through a series of additive and subtractive operations while always maintaining a calculable volume.
- It uses mathematically defined surfaces connected by topology to represent objects as water-tight volumes.
- Solid modelling is preferred for engineering due to its mathematical precision.
- It is accurate in terms of volume and mass and allows for precise shape creation.
- However, it can be complex and time-consuming and requires large system memory.
Surface Modelling
Surface modelling, on the other hand, represents 3D objects as surfaces of connected planar triangles, commonly used for gaming, animation, and digital mockups. It is less intensive than solid modelling but does not allow for cross-sectioning to see internal components.
Surface models are defined by boundaries, UV curves, and surface normals, which determine the outside of the surface. They are useful for scenarios where having the toolpath follow the U or V curves is helpful or in situations where a set of complex solid faces can be condensed into a single surface.
- Surface modelling is the process of constructing a 3D model through the process of defining each of the faces that are present in its geometry.
- It represents 3D objects as surfaces of connected planar triangles.
- Surface models are commonly used for gaming, animation, and digital mockups.
- It provides a fast shape representation and ease of coding.
- However, it is less precise, and engineering accuracy requires very large datasets.
Key Elements of a Solid Object
In solid modelling, there are 4 key elements of a solid object. They are faces, vertices, edges, and volumes. These elements are essential for understanding and working with solid objects in various fields, such as engineering, architecture, and manufacturing.
Here is an explanation of how each element functions in the solid modelling project:
- Faces: A face is a single flat surface of a solid shape, and there can be more than one face of a shape.
- Vertices: A vertex is a point where two or more lines meet, forming a corner. It is also the point of intersection of edges.
- Edges: An edge is a line segment on the boundary joining one vertex (corner point) to another. They serve as the junction of two faces.
- Volume: Every solid shape occupies some volume, which is not the case in a two-dimensional object.
Understanding how each element works in a solid modelling project is essential for accurately representing and manipulating 3D objects. Designers can create detailed and realistic models by defining faces, vertices, edges, and volume.
While solid modelling techniques can help you create 3D objects, as a designer, you must also understand drafting standards.
Drafting standards are a set of guidelines and rules used in the construction industry to ensure the consistency and accuracy of technical drawings.
Learn more about it in our post, “Drafting Standards: What They Are and How They Are Implemented”.
Conclusion
With the use of solid modelling, designers are able to produce precise three-dimensional objects in modern CAD systems. It is of utmost importance in fields like engineering, architecture, and manufacturing.
Through an understanding of surface modelling and solid modelling techniques, engineers and designers can take advantage of solid modelling’s advantages to innovate and streamline their design workflows. Solid modelling is an important part of the BIM process.
So, are you ready to use the BIM process for your construction project?
BIMscaler’s consulting and management services will provide you with end-to-end BIM usage for your project, starting with BIM/model management, content management, project start-up, project meetings, and end-user support, including as-built documentation creation.
As a leading Australian provider of BIM services, BIM Scaler assures you of a professional and effective BIM implementation for your building project.
