“…1, the inner envelope curves do not contribute to the offset and convolution boundaries; their elimination is a direct consequence of the condition: C 1 (t), C 2 (s(t)) > 0. Offset and convolution computations are classic operations in CAD/CAM, which can be used in various interesting geometric applications such as NC machining [8,17], motion planning [3,16,27], character font and brush stroke design [13,14], blending [30], and shape transformation [21].…”