---
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 + NumPad +`

### Difference

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

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

Hotkey: `Alt + NumPad −`

### Intersect

Keep only the volume where both shapes overlap.

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

Hotkey: `Alt + NumPad /`

### Slice *(tool-level)*

Cut the active object with the target and keep both halves as separate volumes. Slice is only available from the [draw tool](../interface/draw-tool.md) — the Boolean modifier's *Operation* dropdown contains Difference, Union, and Intersect only.

![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**.

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

## Setup

1. Select source objects, then make the destination active.
2. Add a Boolean modifier (toolbar button, pie menu, or hotkey).
3. Set the **Target** pointer to the operand object.
4. Choose the **Operation**.
5. Optionally raise **Blend Radius** for a smooth transition.

## Parameters

- **Target** — the other Chisel object used as the operand.
- **Operation** — Difference / Union / Intersect. *(Slice is a tool-level operation that creates two modifiers; see [Slice](#slice-tool-level) above.)*
- **Blend Radius** — 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`, 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

- [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