What Is the Flatten Brush Used for in Blender?

The Flatten brush in Blender is an essential sculpting tool designed to level out surface vertices toward a single average plane. Primarily used to create flat surfaces, sharp angles, and hard-surface details on 3D models, it helps digital sculptors transition between soft organic forms and rigid geometric structures. This guide covers how the Flatten brush works, its primary applications, key settings, and practical tips for improving your 3D sculpting workflow in Blender.

How the Flatten Brush Works

When you drag the Flatten brush over a 3D mesh in Sculpt Mode, Blender calculates the average height and position of all the vertices within the brush radius. It then pulls high points down and pushes low points up, bringing all affected vertices onto that single average height plane.

Unlike smoothing tools that blur detail together, the Flatten brush actively creates planar surfaces while retaining the boundary definition around the sculpted area.

Key Uses for the Flatten Brush

1. Planar Sculpting and Blocking Out Forms

Before adding fine details, artists use planar sculpting to define the main structural planes of a character or object. The Flatten brush is ideal for:

Establishing the major planes of a human face (forehead, cheekbones, jawline).
Blocking out stylized characters with sharp, cell-shaded aesthetic styles.
Defining the broad structural silhouettes of creatures and monsters.

2. Hard-Surface Sculpting

While Blender offers dedicated hard-surface modeling tools, the Flatten brush allows you to sculpt hard-surface elements directly in Sculpt Mode. Common examples include:

Creating armor plates, helmets, and mechanical parts.
Sculpting architectural elements like stone blocks, tiles, or wooden planks.
Forming flat faces on weapons, shields, and sci-fi props.

3. Cleaning Up Rough Meshes

After using dynamic topology (Dyntopo) or high-intensity sculpting tools like Clay Strips, surfaces can become uneven or noisy. The Flatten brush rapidly cleans up unwanted bumps and restores clean, smooth surfaces without reducing the overall volume as much as the standard Smooth brush does.

4. Creating Beveled and Sharp Edges

By running the Flatten brush along the edge where two planes meet, you can manually create crisp bevels and chamfers. This adds realistic highlight edges to hard-surface assets, making them catch light effectively during rendering.

Essential Flatten Brush Settings

To get the most control out of the Flatten brush, adjust these settings in the Tool Properties panel:

Strength: Controls how aggressively vertices move toward the average plane. Lower strength values (0.2–0.5) offer smoother control, while higher values instantly create flat planes.
Plane Offset: Adjusts the height of the flattening plane relative to the surface. Raising this value pushes the flattened plane outward, while lowering it sinks the plane deeper into the mesh.
Area Normal: Determines how the brush calculates the flat plane's orientation. Enabling this ensures the brush aligns precisely with the surface angle directly under the cursor center.
Auto-Smooth: Blends the edges of the flattened region seamlessly into the surrounding mesh, preventing unintended ridges along the border of your brush strokes.

Flatten vs. Scrape vs. Polish Brushes

Blender includes several brushes with similar functionality, but each serves a specific purpose:

Flatten Brush: Averages all vertices under the brush, pulling low areas up and high areas down equally.
Scrape Brush: Cuts off high points (peaks) while leaving low points untouched, making it ideal for shaving down excess geometry.
Fill/Deepen Brush: Fills in low points (valleys) without trimming down high areas.
Polish Brush: A gentler version of the Scrape/Flatten combination, designed for fine finishing touches on hard-surface models.