Blender Weight Gradient Tool Explained

The Weight Gradient tool in Blender is a specialized feature used within Weight Paint mode to apply smooth, gradual weight values across vertex groups. Essential for character rigging, animation, and particle distribution, this tool allows artists to blend weights seamlessly across a 3D mesh using linear or radial gradients. This guide covers how the tool works, key options, and practical steps for using it effectively in your 3D workflow.

What Is the Weight Gradient Tool?

In Blender, weight painting assigns influence values (ranging from 0.0 to 1.0) to vertices within a vertex group. These weights dictate how much an armature bone, modifier, or particle system affects specific parts of a mesh.

Instead of manually brushing weights onto individual vertices, the Weight Gradient tool lets you click and drag a line across your object to generate a smooth transition of weight values automatically.

Types of Weight Gradients

Blender offers two main types of gradients in the tool options:

  • Linear Gradient: Applies weights in a straight line from the start point to the end point of your drag line. Vertices before the start point receive maximum weight, while vertices past the end point receive minimum weight.
  • Radial Gradient: Applies weights outward in a circular pattern from the center point where you first click, fading toward the outer boundary of the drag distance.

How to Use the Weight Gradient Tool

  1. Select Your Object: Click on your mesh in Object Mode.
  2. Enter Weight Paint Mode: Switch the mode interaction menu (top-left of the 3D Viewport) from Object Mode to Weight Paint.
  3. Select a Vertex Group: Open the Object Data Properties tab (green triangle icon) and choose the vertex group you want to modify.
  4. Activate the Tool: Select the Gradient Tool from the left toolbar, or press the shortcut key (often bound to G or accessible via the toolbar menu).
  5. Adjust Tool Parameters: In the top bar, set your desired Weight value (e.g., 1.0 for full influence or 0.0 for none) and Strength (opacity of the operation).
  6. Apply the Gradient: Click and drag across your mesh in the 3D Viewport, then release the mouse button to draw the gradient vector.

Key Tool Settings

  • Weight: Sets the target weight value applied at the start of the gradient stroke.
  • Strength: Controls how strongly the new gradient replaces or blends with existing weights.
  • Blend Mode: Determines how the gradient interacts with existing weights. Common modes include:
    • Mix: Replaces existing weight values with the new gradient.
    • Add: Adds the gradient values to current weights.
    • Subtract: Reduces current weights based on the gradient values.

Common Practical Applications

  • Character Rigging: Creating smooth bend falloffs for joints like elbows, knees, and spines so the mesh deforms naturally when bones move.
  • Environment Design: Blending particle distribution density for grass, trees, or debris so objects fade out naturally toward edges.
  • Modifier Control: Controlling mask falloffs for modifiers like Deform, Mask, or Displace across complex geometry.