Pictorial drawings are essential in architectural design communication as they provide three-dimensional views of buildings and structures, offering clients and stakeholders a clear visual understanding beyond flat plans and elevations. In Kenya’s growing construction industry, where diverse clients often lack technical drawing literacy, pictorial representations enhance project approval and collaboration among architects, contractors, and regulatory bodies. This chapter focuses on producing isometric and oblique drawings, two fundamental pictorial techniques that balance visual clarity with ease of construction using standard architectural conventions.

4.1 Isometric Drawings Production

Isometric drawings are widely used in architecture to represent three-dimensional objects on a two-dimensional plane, preserving scale along all three principal axes. This technique is valuable in Kenyan architectural practice for conceptual presentations, detailing complex structural elements, and coordinating multidisciplinary design inputs. Understanding how to convert orthographic projections, specifically first and third angle views, into isometric drawings is critical for accuracy and professional presentation.

4.1.1 First Angle to Isometric

First angle projection is a method where the object is conceptually placed between the observer and the plane of projection, commonly used in Kenya for technical architectural drawings. Converting first angle orthographic views into isometric drawings involves interpreting the front, top, and side elevations accurately to construct a scaled three-dimensional representation.

Meaning of First Angle Projection

• Object placement is between the observer and the projection plane, meaning views are arranged opposite to their real-world positions.
• View order: The top view is placed below the front, and the right side view is to the left of the front.
• Standard use: Though less common in Kenya compared to third angle, it is still important in some architectural documentation.
• View interpretation requires mental rotation to align views correctly for isometric construction.
• Line conventions follow BS EN ISO 128 standards, ensuring clarity and uniformity.

Procedure for Converting First Angle to Isometric

1. Identify orthographic views: Locate the front, top, and side views on the first angle projection sheet.
2. Draw the isometric axes: Using a 30° angle from the horizontal for both left and right axes, and a vertical axis, establish the isometric framework.
3. Transfer height from front view: Measure vertical dimensions from the front elevation and plot along the vertical isometric axis.
4. Transfer depth from side view: Use the side elevation to determine depth, plotting along the right 30° axis.
5. Transfer width from top view: Extract width dimensions from the plan and plot along the left 30° axis.
6. Connect points: Join corresponding points in the isometric space to form the object outline.
7. Add details: Include doors, windows, and other architectural features following the isometric scale.
8. Use line types: Apply continuous thick lines for visible edges, dashed lines for hidden edges per BS EN ISO 128.
9. Dimensioning: Provide dimensions parallel to the isometric axes without distortion.

Characteristics of Isometric Drawings from First Angle

• Equal scale along all axes preserves proportions without perspective distortion.
• Angles between axes are fixed at 120°, facilitating consistent measurements.
• No foreshortening: All dimensions are drawn to scale.
• Clarity in complex forms: Multiple architectural components can be visualized simultaneously.
• Easily interpreted by Kenyan contractors familiar with standard architectural drawings.

4.1.2 Third Angle to Isometric

Third angle projection is the standard in Kenya for architectural drawings, where the object is placed behind the projection plane. Architects must skillfully convert these views into isometric drawings for presentations and detailed design communication.

Meaning of Third Angle Projection

• Object placement is behind the projection plane, so views correspond directly to the object’s sides.
• View order: The top view is above the front, and the right side view is to the right.
• Widely adopted in Kenya for architectural and engineering drawings due to international standards.
• View clarity: Easier to interpret for those familiar with building plans and elevations.
• Conforms to BS EN ISO 5456-2 for orthographic projections.

Steps to Convert Third Angle to Isometric

1. Locate front, top, and side views on the third angle projection sheet.
2. Sketch isometric axes at 30° left and right from horizontal and vertical axis.
3. Plot vertical heights from the front elevation along the isometric vertical axis.
4. Plot widths from the top view along the left 30° axis.
5. Plot depths from the side view along the right 30° axis.
6. Mark intersection points corresponding to corners of the structure.
7. Draw connecting edges to form the three-dimensional shape.
8. Incorporate architectural features such as wall thickness, openings, and roof slopes.
9. Apply correct line weights and types per architectural drawing standards.
10. Dimension appropriately, ensuring clarity for contractors and clients.

Advantages of Third Angle Isometric Drawings in Architecture

• Direct correlation with orthographic views simplifies interpretation.
• Widely accepted by Kenyan architectural firms and regulatory bodies.
• Facilitates coordination between design and construction teams.
• Supports detailed presentation of complex building elements.
• Improves client understanding through realistic visualization.

Chapter Summary

This chapter focused on the production of pictorial drawings, beginning with isometric drawings where techniques for converting first angle and third angle orthographic projections into isometric views were explained. It detailed the step-by-step construction procedures to achieve accurate isometric representations that maintain proportional dimensions. The chapter then covered oblique drawings, illustrating how to transform first angle and third angle projections into oblique views by applying the appropriate scale and angle conventions. Emphasis was placed on the proper use of standard line types and scales in line with BS and ISO standards. Finally, the chapter explored perspective drawings, introducing both one-point and two-point perspective methods to represent objects realistically as they appear to the human eye. Interpretation skills were developed alongside production techniques to enable clear and precise perspective sketches. Throughout the chapter, the importance of adhering to technical drawing standards and conventions was highlighted to ensure clarity and uniformity in pictorial representations.