In freehand oblique sketching used for quick 3D communication, what are the most commonly adopted angles for the receding (depth) lines to balance readability and distortion while keeping construction simple?

Introduction / Context:
Oblique sketching is a rapid pictorial technique. The front face is drawn in true shape, while the depth is projected along receding lines at a chosen angle. The choice of receding angle affects visual clarity, apparent distortion, and ease of construction.

Given Data / Assumptions:

• The question concerns common practice, not an absolute rule.
• Angles should be easy to lay out and result in reasonable depth perception.
• We consider standard classroom and industry habits.

Concept / Approach:

Typical receding angles for oblique sketches are 30° or 45°. At 45°, construction is quick and symmetrical; at 30°, distortion is reduced, giving a slightly more natural look. Depth scaling (full, half, or two-thirds) is often applied—especially at 45°—to minimize exaggeration in cavalier vs. cabinet styles.

Step-by-Step Solution:

Verification / Alternative check:

Textbooks and drafting standards frequently show worked examples at 45° and 30°. Many templates and protractors also highlight these angles for convenient sketching.

Why Other Options Are Wrong:

15°, 25°, or 60° are possible but less common in teaching and practice for quick sketches, offering either too shallow or too steep impressions.

Common Pitfalls:

Using full depth at 45° (cavalier) can exaggerate depth; consider cabinet oblique with half-depth scaling for better realism.

Final Answer:

30 or 45 degrees