The best way to cut a polygon 3D model is using boolean operations (e.g., subtract) or specialized tools (like split/knife) in 3D software—these balance speed and precision.
Boolean operations use a "cutter" object to trim the target model; ideal for simple, clean cuts.
Specialized tools like Blender’s Knife Tool or Maya’s Split Polygon Tool let you draw custom lines for detailed control over where you cut.
For clean results, ensure both the model and cutter are manifold (no gaps/overlaps) and test small sections first to avoid broken geometry.