3.2.2 Principles of Graphical Modelling Notes

Differentiating Between 2D and 3D Graphical Models

Imagine you're designing a new piece of furniture, a sleek, modern chair. Before production can begin, you need to visualize your ideas and communicate them to your team. This is where graphical models become essential. But should you start with a quick 2D sketch or dive straight into a detailed 3D model? Let’s break down the differences between these two modeling approaches and their roles in the design process.

2D Graphical Models: The Foundation of Ideas

A2D graphical model represents an object using two dimensions: height and width. These models are often the first step in the design process because they are quick to create and effective for brainstorming. Common examples include freehand sketches, diagrams, and orthographic projections.

• Advantages:
  • Quick and simple to produce.
  • Useful for communicating basic ideas and structural layouts.
  • Ideal for isolating specific features or creating technical drawings.
• Limitations:
  • Cannot fully represent the depth or form of an object.
  • May not effectively convey complex designs or spatial relationships.

For instance, a 2D sketch of your chair might include front and side views, helping you determine its overall shape and proportions. However, it won’t provide a sense of how the chair would look in a physical environment or how its components interact.

3D Graphical Models: Adding Depth and Realism

A3D graphical model represents an object in three dimensions: height, width, and depth. These models are often created using CAD (Computer-Aided Design) software and are essential for visualizing the form, fit, and aesthetics of a design.

• Advantages:
  • Provides a realistic representation of the object, including depth and spatial relationships.
  • Allows for virtual manipulation, such as rotating the model or simulating assembly.
  • Useful for identifying design flaws and testing ergonomics.
• Limitations:
  • Requires more time, skill, and resources to create.
  • Less effective for quick brainstorming or early-stage ideation.

When designing your chair, a 3D model would allow you to view it from all angles, experiment with different materials, and simulate how it might look in a room. This level of detail is invaluable for refining your design and preparing for production.

Drawing Techniques: Perspective, Projection, and Scale Drawings

Now that you understand the types of graphical models, let’s explore the drawing techniques used to create them. Whether sketching by hand or using CAD software, the choice of technique depends on the purpose of the drawing.

Perspective Drawings: Mimicking the Human Eye

Perspective drawings create a realistic representation of an object as it appears to the human eye. They use vanishing points to simulate depth, making objects appear smaller as they recede into the distance.

• Single-point perspective: All lines converge at one vanishing point, often used for objects directly facing the viewer.
• Two-point perspective: Lines converge at two vanishing points, commonly used in architectural and product design.
• Three-point perspective: Adds a third vanishing point for vertical lines, creating a dynamic view from above or below.

For example, a perspective drawing of your chair might depict it in a room, emphasizing its size and spatial relationship with other furniture.

Projection Drawings: Accurate and Informative

Projection drawings use parallel lines to project the dimensions of an object onto a flat plane. Unlike perspective drawings, they do not simulate depth, making them ideal for technical purposes.

• Orthographic projection: Depicts multiple views (e.g., front, top, side) of an object, providing precise dimensions.
• Isometric projection: Represents an object in three dimensions without distortion, often used for technical illustrations.

Orthographic drawings of your chair would include detailed measurements, ensuring manufacturers can accurately produce each component.

Scale Drawings: Adjusting Size for Clarity

Scale drawings represent objects at a specific ratio relative to their actual size. For example, a scale of 1:10 means that 1 unit on the drawing equals 10 units in real life.

• Uses:
• Enlarging small objects for clarity.
• Reducing large objects to fit on a page.
• Maintaining proportional relationships.

A scale drawing of your chair might be used to plan its placement in a room or compare its size with other furniture.