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Knife Tool – Blender 2.80 Fundamentals

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This tutorial is part of the Blender Fundamentals series, produced by Dillon Gu.

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Knife Tool in Blender #

The Knife tool in Blender allows you to make precise cuts on your mesh geometry, enabling you to create new topology or modify existing topology to better suit your modeling needs. This guide will cover how to use the Knife tool and its various options, as well as some tips for effective use.

Using the Knife Tool #

To use the Knife tool in Blender, follow these steps:

  1. Select a mesh object.
  2. Press ‘Tab’ on your keyboard or choose ‘Edit Mode’ from the interaction mode dropdown menu in the 3D viewport’s top-left corner.
  3. Press ‘K’ on your keyboard to activate the Knife tool.
  4. Left-click on a starting point for your cut.
  5. Move the mouse cursor to draw the cut line, and left-click to place additional cut points as needed.
  6. To finish the cut, press ‘Enter’ or right-click. To cancel the cut, press ‘Esc’.

Knife Tool Options #

While using the Knife tool, you can access several options for greater control over your cuts:

  • Constrained Cut: Press ‘C’ to constrain the cut angle to 45-degree increments.
  • Cut Through: Press ‘Z’ to enable the cut to go through the entire mesh, affecting both the visible and occluded geometry.
  • Ignore Snapping: Press ‘Shift’ to temporarily disable snapping to vertices, edges, and faces while cutting.

Knife Tool Tips #

  1. Cut at Midpoints: The Knife tool snaps to the midpoint of an edge when the mouse cursor is close to it. Use this feature to create evenly-spaced cuts.
  2. New Edge Loops: To create a new edge loop using the Knife tool, start your cut on an existing vertex or edge and continue cutting parallel to the existing loop.
  3. Non-Destructive Cutting: To create a non-destructive cut that does not affect the mesh’s shading, cut along the mesh’s existing edges.
  4. Cleaning Up Cuts: After using the Knife tool, it is essential to check your mesh for any unwanted topology or shading artifacts. Use the Merge Vertices or Remove Doubles tools to clean up any duplicate vertices or overlapping geometry.

By mastering the Knife tool and its various options and techniques, you can make precise and complex cuts to your mesh geometry, enabling you to create or modify topology to better suit your modeling needs in Blender.

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