---
title: Primitives
order: 3
---

Primitives are the building blocks of every Chisel scene. Each one is defined by a math function, so surfaces stay perfectly smooth at any scale and rounding is a constant — not a subdivision setting.

![Pie menu with primitives](../assets/pie-menu.webp)

## Adding a primitive

Three ways to create one:

- **`Shift + A → Chisel`** — Blender's add menu, with custom Chisel icons
- **`Q` (pie menu) → North-West** — primitive grid
- **Draw tool** — activate the Chisel tool in the toolbar, then **LMB-drag** in the viewport. The primitive is placed under the cursor and scaled live as you drag.

The draw tool aligns the new primitive based on its *Align* option:

| Align | Behavior |
|---|---|
| **Normal** *(default)* | Surface normal under the cursor |
| **World** | World axes |
| **Local** | Object-local axes under the cursor |
| **Cursor** | Blender's 3D Cursor orientation |

Press `D` while the draw tool is active to open the shape and operation picker popup. Use it to set the shape that the next drag spawns (*Box*, *Sphere*, *Cylinder*…) and the operation (*Add*, *Difference*, *Union*, *Intersect*, *Slice*, *Emboss*, *Engrave*) without leaving the viewport. The `D` picker lists the eight mesh shapes only — curve types are added from the `Shift + A → Chisel` or pie grids.

## Changing the type after creation

A primitive's type isn't locked in. To swap an existing shape to another:

- **`[` / `]`** *(Chisel tool only)* — cycle the active primitive's type
- **`RMB → Type`** — pick any type from the submenu; the current one is highlighted
- **Pie grid (`Shift + click`)** — `Shift`-click a primitive button to swap every selected shape to that type

Swapping is **family-locked**: the eight mesh shapes form one family and the three curve types form another, and a swap never crosses between them. Try to switch a Box to a Curve and Chisel skips it and reports how many objects were incompatible.

## Common parameters

Every primitive lives on a regular Blender object. Its SDF settings are in the *Object Properties* panel under the Chisel section.

- **Is Chisel** — toggle SDF mode on/off
- **Primitive Type** — change the shape after creation
- **Half-Extents (X, Y, Z)** — bounding extents along each axis, derived from the object's scale
- **Rounding** *(most primitives)* — edge radius (`0.0–10.0`, soft max `2.0`, default `0.0`)
- **Profile** *(most primitives)* — Round / Sharp / Soft / Tight / Chamfer
- **Chamfer Smooth** *(only when Profile = Chamfer)* — softens where the chamfer meets the faces (`0.0–5.0`)

Sphere, Torus, and Capsule have no rounding option — their surfaces are already smooth by construction.

## Categories

- **[Standard Shapes](shapes.md)** — Box, Sphere, Cylinder, Cone, Capsule, Torus, Prism, Trapezoid
- **[Curve-Based](curves.md)** — Curve (extruded 2D), Curve Tube (3D Bezier sweep), Curve Revolve (profile revolution)

## Quick reference

| Primitive | Key parameters | Rounding | Bevel |
|---|---|:---:|:---:|
| [Box](shapes.md#box) | Size, half-extents | ✓ | — |
| [Sphere](shapes.md#sphere) | Radius | — | — |
| [Cylinder](shapes.md#cylinder) | Radius, depth | ✓ | — |
| [Cone](shapes.md#cone) | Radius 1, Radius 2, depth, cap | ✓ | — |
| [Capsule](shapes.md#capsule) | Radius, depth | — | — |
| [Torus](shapes.md#torus) | Major, minor radius | — | — |
| [Prism](shapes.md#prism) | Sides, apex angle | ✓ | ✓ |
| [Trapezoid](shapes.md#trapezoid) | Size, cap | ✓ | ✓ |
| [Curve](curves.md#curve) | Depth | ✓ | — |
| [Curve Tube](curves.md#curve-tube) | Tube radius | — | — |
| [Curve Revolve](curves.md#curve-revolve) | Revolve angle | — | — |