Fig. 1

This computer mouse sketch began with intersecting orthographic and sectional profiles over which compound curves for the outline and parting line were laid.

The Cartesian grid reconsidered

The Cartesian grid is the ideal tool for situating flat sketch geometry whether orthographic or sectional. However, it doesn’t help greatly when the sketch cannot be confined to a flat plane. This is the case with a compound curve or 3D sketch, which resembles the outer edge of Harry Bertoia’s Diamond lounge chair for Knoll Furniture (fig. 3).

The line of the chair moves along multiple planes simultaneously. Like the track of a roller coaster—no section ...

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