- Understanding Solid Objects
- Understanding Sketching Techniques
- 3.1 Technique of Lines
- 3.2 Sketching Straight Lines
- 3.3 Sketching Circles, Arcs, and Ellipses
- 3.4 Maintaining Proportions
- 3.5 One-View Drawings
- 3.6 Pictorial Sketching
- 3.7 Projection Methods
- 3.8 Axonometric Projection
- 3.9 Isometric Projection
- 3.10 Isometric Drawings
- 3.11 Making an Isometric Drawing
- 3.12 Offset Location Measurements
- 3.13 Hidden Lines and Centerlines
- 3.14 Angles in Isometric
- 3.15 Irregular Objects
- 3.16 Curves in Isometric
- 3.17 True Ellipses in Isometric
- 3.18 Orienting Ellipses in Isometric Drawings
- 3.19 Drawing Isometric Cylinders
- 3.20 Screw Threads in Isometric
- 3.21 Arcs in Isometric
- 3.22 spheres in Isometric
- 3.23 Oblique Sketches
- 3.24 Length of Receding Lines
- 3.25 Choice of Position in Oblique Drawings
- 3.26 Ellipses for Oblique Drawings
- 3.27 Angles in Oblique Projection
- 3.28 Sketching Assemblies
- 3.29 Sketching Perspectives
- 3.30 Curves and Circles in Perspective
- 3.31 Shading
- 3.32 Computer Graphics
- 3.33 Drawing on Drawing
- Key Words
- Chapter Summary
- Worksheets
- Review Questions
- Sketching Exercises

## 3.22 spheres in Isometric

The isometric drawing of any curved surface can be constructed from all lines that can be drawn on that surface. For spheres, select the great circles (circles cut by any plane through the center) as the lines on the surface. Because all great circles, except those that are perpendicular or parallel to the plane of projection, are shown as ellipses having equal major axes, they enclose a circle whose diameter is the major axis of the ellipse.

Figure 3.54 shows two given views of a sphere enclosed in a construction cube. Next, an isometric of a great circle is drawn in a plane parallel to one face of the cube. There is no need to draw the ellipse, since only the points on the diagonal located by measurements *a* are needed to establish the ends of the major axis and thus to determine the radius of the sphere.

**3.54** Isometric of a Sphere

In the resulting isometric drawing, the diameter of the circle is times the actual diameter of the sphere. The isometric projection is simply a circle whose diameter is equal to the true diameter of the sphere.