Chisel
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Chisel

A small sphere joined onto a larger one, then the seam filleted
Union
A small sphere cutting a bowl out of a larger one
Difference
Only the overlap of two spheres is left
Intersect
A sphere sliced along a smaller one; the cut-out piece is a shape of its own
Slice
A small sphere sitting in its own pocket in a larger one, the gap widening
Carve
The rim of a cut in a sphere blended round, then chamfered, then round again
Blend

Chisel is an SDF modeling add-on for Blender. You build a model from shapes, such as boxes, cylinders and tubes, and combine them with operations such as cuts and joins. The shapes are not made of polygons: Chisel draws them directly from their mathematical description.

Implicit modeling

A mesh stores its surface as vertices joined by faces. A curved surface is approximated by flat faces, and a smoother curve needs more of them.

An implicit shape is described by a formula instead. A sphere, for example, is all the points closer to its centre than its radius. Because the formula can be evaluated at any point, a curved surface stays curved however far you zoom in.

Signed distance fields

Chisel describes every shape with a signed distance field (SDF): a function that returns, for any point in space, the distance from that point to the nearest surface of the shape. The value is positive outside the shape, negative inside and zero on the surface. The direction in which the distance changes fastest is the surface normal, which Chisel uses for shading.

What this means when you model

  • Curved surfaces stay smooth at any zoom. There is no subdivision level and no topology to manage.
  • Booleans combine the distance values directly. A union takes the smaller of the two distances at each point, an intersection the larger, and a difference first swaps the inside and outside of the cutter. No faces are cut, so the result is always a closed surface, without holes or flipped normals.
  • A join can be blended: turn on its Blend and the seam between the two shapes becomes a fillet of the radius you set. You can change the radius at any time.
  • A shape’s edges are rounded by its Rounding value, without adding geometry, and the value stays editable.
  • Joins and modifiers stay editable after you add them. Moving a cutter, reordering the stack or changing a value updates the model.

A slab with a post joined on and a dimple cut in; the Blend of both joins rises from 0 and back

Limitations

  • You model by adding shapes and combining them, not by editing vertices. The corners of an Ngon and the points of path shapes such as the Tube can be moved, but there is no vertex or face editing.
  • Exporting, UV unwrapping, sculpting and game engines need a mesh. Convert to Mesh creates one at the resolution you choose, and Convert to SDF turns a mesh into a Chisel shape.
  • The viewport is computed on the graphics card, and large scenes can slow it down. Quality and Performance have the settings for that.

How Chisel draws shapes

Chisel has its own render engine. For each pixel, it follows the line of sight from the camera in steps. Each step is as long as the distance the field returns at that point, since nothing can be closer than that. When the distance is almost zero, the ray has reached the surface. This is called ray marching. To stay fast, the viewport keeps detail only down to a set size (World Cell Size); an F12 render always computes the exact surface. Implicit Modeling explains the math.

Blender still needs a mesh for selecting, snapping, Solid shading, EEVEE and Cycles. For a shape with modifiers, Chisel keeps a low-resolution proxy mesh of the result and updates it after each edit.

A V8 engine block modelled entirely with Chisel SDF shapes

Every bore, bolt hole and boss of this engine block is a Chisel shape: no polygons until you convert.

Start here

  1. Installation: requirements, installing the extension, the render engine and the first shader compile
  2. Core Concepts: the terms this manual uses

If you used Chisel 4.x, the changelog lists what changed in 5.0.

Sections

  • Getting Started: installation, core concepts and the math behind implicit modeling
  • Interface: the Chisel tool and its modes, Edit and Block mode, the Tape tree, menus, gizmos, panels and messages
  • Primitives: the ten standard shapes, the path shapes, Text and Mesh
  • Joins: Boolean (Union, Difference, Intersect, Slice), Emboss & Engrave, and Carve
  • Rounding & Blending: edge rounding, seam blends and the five profiles
  • Modifiers: Solidify, Mirror, Bisect, Array, Twist & Bend, Revolve, Sweep, Lattice and Smooth
  • Materials: per-shape colour and the Chisel node editor
  • Operations: convert to mesh and to SDF, apply, rebuild, clean and veil
  • Render Engine: quality, performance, matcap, display, gizmo settings, baking and F12
  • Keymap: every Chisel key
  • Preferences: status, theme colours and debug tools
  • Changelog: what changed in 5.0

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