How to Merge Vertices with Blender Weld Modifier

The Blender Weld Modifier is a powerful, non-destructive tool used to automatically merge nearby vertices within a mesh based on a specified distance threshold. This guide explains how to locate and apply the Weld Modifier, configure its key settings like Distance and Vertex Groups, and use it effectively to clean up geometry, fix seam issues, and optimize 3D models.

How to Apply the Weld Modifier

  1. Select your 3D object in Object Mode.
  2. Navigate to the Properties Panel on the right side of the screen and click the Modifier Properties tab (wrench icon).
  3. Click Add Modifier.
  4. Under the Generate column, select Weld.

Key Settings Explained

  • Distance: This is the most crucial setting. It defines the maximum distance between vertices for them to be merged together.
    • Increase the value to merge vertices that are farther apart.
    • Keep the value low (e.g., 0.001 m) if you only want to remove overlapping or duplicate vertices without altering the overall shape.
  • Vertex Group: Allows you to restrict the weld effect to a specific group of vertices rather than the entire mesh. Click the field and select your predefined vertex group.
  • Invert Icon (<->): Located next to the Vertex Group field, this option reverses the influence, applying the weld to every vertex except those in the selected group.
  • Max Limit: Limits the maximum number of vertices that can be merged into a single vertex. Setting this to 0 removes any limit.

When to Use the Weld Modifier

  • Cleaning Up Imported Models: Imported CAD files or 3D scans often contain duplicate vertices or disconnected geometry. The Weld Modifier quickly fixes these topological errors.
  • Mirror Seam Repair: When using a Mirror Modifier, seam gaps can sometimes appear along the center axis. Placing a Weld Modifier after the Mirror Modifier cleanly merges the center vertices.
  • Simplifying Complex Meshes: You can reduce dense geometry by increasing the Distance threshold, effectively decimating the mesh while maintaining its general volume.

Applying the Modifier Permanently

Because modifiers are non-destructive, the geometry is only merged dynamically in the viewport and renderer. To make the changes permanent on your mesh topology:

  1. Hover your cursor over the Weld Modifier panel.
  2. Press Ctrl + A, or click the dropdown arrow at the top right of the modifier card and select Apply.

Note: You must be in Object Mode to apply modifiers.