---
title: Boolean
order: 1
---

Combine two SDF objects. Chisel booleans operate directly on the distance fields, so the result is clean and re-editable: no mesh repair, no bad normals, no duplicated geometry.

![Boolean settings](../assets/modifierssettings-boolean.webp)

## Operations

### Union

Combine both shapes into a single solid volume.

![Boolean Union](../assets/boolean-union.webp)

Hotkey: `Alt + =` or `NumPad +`

### Difference

Subtract the target from the active object, the classic "cut out" boolean.

![Boolean Difference](../assets/boolean-difference.webp)

Hotkey: `Alt + −` or `NumPad −`

### Intersect

Keep only the volume where both shapes overlap.

![Boolean Intersect](../assets/boolean-intersect.webp)

Hotkey: `Alt + \\` or `NumPad /`

### Slice

Cut the active object with the target and keep both halves as separate volumes. Slice flips the host to Difference and spawns a `{name}_slice` copy set to Intersect. Add it from the [active tool](../interface/active-tool.md), the *Add Modifier* menu, or the pie. The Boolean modifier's *Operation* dropdown itself contains Difference, Union, and Intersect only.

For a difference that cuts with a *grown* copy of the target (and keeps the target visible in its pocket) see [Carve](carve.md).

![Boolean Slice](../assets/boolean-slice.webp)

## Smooth blending

Push the **Blend Radius** above zero and the boolean seam becomes a smooth fillet. No extra geometry, just math. The fillet shape follows the **Blend Profile**. In the panel this slider is labelled *Outer*.

![Smooth blend](../assets/gizmo-blending.webp)

## Setup

1. Select source objects, then make the destination active.
2. Add a Boolean modifier (Add Modifier menu, pie menu, or hotkey).
3. Set the **Target** to the operand object. Picking a target by hand in the panel hides it from the render, the same as the operators do, so the cutter never fills the hole it cuts.
4. Choose the **Operation**.
5. Optionally raise **Blend Radius** for a smooth transition.

## Swap the operation

**Swap Modifier** (the *Shift+click* of the boolean buttons in the pie and the `RMB` menu's *Modifiers* submenu) rewrites every modifier that targets the selected shapes to a new operation at once. The buttons sit four to a row (Difference, Union, Intersect, Slice, then Emboss, Engrave, Carve) and light up when the selected shape is already used that way. The cycle hotkeys `;` and `'` step the active boolean through Difference → Union → Intersect → Emboss → Engrave → Carve (Slice excluded).

## Parameters

- **Target**: the operand object. The field is a native object search box labelled *Target*; type or pick the operand by name.
- **Operation**: Difference / Union / Intersect. *(Slice creates two modifiers and isn't in this dropdown; see [Slice](#slice) above.)*
- **Blend Radius** (labelled *Outer* in the panel): fillet radius at the seam (`0.0–10.0`, soft max `2.0`). `0.0` = sharp boolean.
- **Blend Profile**: Round / Sharp / Soft / Tight / Chamfer.
- **Blend Smooth** *(Chamfer profile only)*: softens the chamfer's outer edges.
- **Material Blend**: width multiplier for the *color* blend across the seam (`0.0–10.0`, soft max `3.0`, default `1.0`). `1.0` = color follows geometry; higher = color bleeds wider; `0.0` = color snaps even on smooth seams.

When `Blend Radius > 0`, *Use Smooth* is auto-enabled. See [Rounding & Blending](../rounding-and-blending/index.md) for the profile shapes.

## See also

- [Carve](carve.md): a difference that cuts with a grown, still-visible target
- [Smooth](smooth.md): one blend radius for every seam in the model
- [Mirror](mirror.md): symmetry as an SDF reflection
- [Emboss & Engrave](emboss-engrave.md): separate inner / outer fillets
- [Operations: Clean](../operations/clean.md): detach a boolean operand from the stack