How to Taper Curves with a Taper Profile in Blender

Tapering a curve object using another curve in Blender allows you to create dynamic, non-destructive variations in thickness along the length of a curve. By assigning a secondary curve as a "Taper Object" inside the primary curve's geometry properties, you can precisely control the radius from start to finish. This guide explains how to set up the primary curve, shape the taper profile, and configure the settings for real-time dynamic tapering.

1. Create the Primary Curve

  1. Press Shift + A in the 3D Viewport and navigate to Curve > Bézier (or NURBS Path).
  2. With the curve selected, go to the Object Data Properties tab (the green curve icon) in the Properties panel.
  3. Expand the Geometry section, then expand the Bevel sub-section.
  4. Set the Depth value higher than 0 (e.g., 0.2 m) to give the curve volume.

2. Create the Taper Curve

  1. Press Shift + A and add a second curve to your scene (such as a Bézier Curve).
  2. Rename this curve to Taper_Profile in the Outliner for easy reference.
  3. Ensure the scale of both curves is applied by selecting each and pressing Ctrl + A > Apply All Transforms or Scale.

3. Assign the Taper Object

  1. Select your primary curve.
  2. Go back to Object Data Properties > Geometry > Bevel.
  3. Locate the Taper Object field beneath the Bevel settings.
  4. Click the field and select your Taper_Profile curve (or use the eyedropper tool to click it in the viewport).

4. How the Taper Curve Controls Thickness

Blender maps the coordinates of the taper curve to the main curve based on local axes:

  • X-Axis (Length): The local X-axis of the taper curve represents the start-to-end length of the primary curve. The leftmost point along the local X-axis corresponds to the start of the primary curve, while the rightmost point corresponds to the end.
  • Y-Axis (Radius/Thickness): The vertical distance of the taper curve's control points from its local origin (the center point) determines the thickness. Moving a point higher above the origin increases thickness; placing a point directly on the local origin sets the thickness to zero.

5. Adjust the Profile Dynamically

  1. Select the Taper_Profile curve and press Tab to enter Edit Mode.
  2. Move, rotate, or scale the control points along the X and Y axes.
  3. Observe the primary curve updating its cross-sectional width dynamically in real time.
  4. To create sharp tips or flat profiles, adjust the handle types of the taper curve by pressing V and choosing Aligned, Free, or Vector.