Abstract: We present a novel sketch-based tool, called iCutter (short for intelligent cutter), for cutting out semantic parts of 3D shapes. When a user performs a cutting task, he only needs to draw a freehand stroke to roughly specify where cuts should be made without much attention. Then, iCutter intelligently returns the best cut that meets the user's intention and expectation. We develop a novel scheme for selecting the optimal isoline from a well-designed scalar field induced from the input stroke, which respects the part saliency as well as the input stroke. We demonstrate various examples to illustrate the flexibility and applicability of our iCutter tool.