How to Use the Blob Brush in Blender

The Blob Brush in Blender is a specialized sculpting tool designed to add spherical, volume-expanding geometry to a 3D mesh. This guide provides a clear breakdown of how to locate, configure, and effectively use the Blob Brush in Sculpt Mode to quickly build up organic shapes, add muscular detail, and refine your 3D sculpts.

1. Accessing the Blob Brush

  1. Select the 3D mesh you want to sculpt in the 3D Viewport.
  2. Switch from Object Mode to Sculpt Mode using the mode dropdown menu in the top-left corner (or press Ctrl + Tab and select Sculpt).
  3. Open the toolbar on the left side of the viewport by pressing T if it is not visible.
  4. Click on the Blob brush icon from the toolbar.

2. Essential Brush Shortcuts

  • Adjust Radius: Press F and move your mouse to change the brush size. Left-click to confirm.
  • Adjust Strength: Press Shift + F and move your mouse to change the brush intensity. Left-click to confirm.
  • Invert Effect (Subtract): Hold Ctrl while painting to pull geometry inward instead of pushing it outward.
  • Quick Smooth: Hold Shift while painting to temporarily activate the Smooth brush and blend the blobbed areas into the surrounding mesh.

3. Configuring Key Settings

You can adjust the Blob Brush settings in the Tool Settings bar at the top of the viewport or in the right-hand Properties Panel under the Active Tool tab.

  • Radius and Strength: Set base values for brush size and intensity. Enable the pressure sensitivity icons next to these values if you are using a drawing tablet.
  • Hardness: Found under the Falloff section. Higher values make the blob edges sharper, while lower values create softer, more gradual volume changes.
  • Auto-Smooth: Set a value above 0.000 to automatically smooth the geometry as you apply the blob, reducing jagged edges.

4. Using Dynamic Topology (Dyntopo)

When using the Blob Brush to heavily expand a mesh, the existing polygon faces can stretch and distort.

  1. Expand the Dyntopo panel in the top-right corner of the viewport and check the box to enable it.
  2. Set the Detailing method (e.g., Relative Detail or Constant Detail).
  3. Paint with the Blob Brush; Blender will automatically generate new polygons in real-time to maintain geometric density without stretching.

5. Practical Applications

  • Organic Sculpting: Ideal for adding muscles, fat deposits, skin folds, and rounded features on characters or creatures.
  • Base Form Creation: Great for rapidly blocking out initial shapes and silhouettes from a simple base mesh like a UV Sphere or Cube.
  • Stylized Details: Useful for creating cartoonish protrusions, droplets, or stylized hair clumps.