Spline Tool

spline_dat/Tool_bline_icon.png ALT-B


Splines are the most used objects in any normal animation done with Synfig, and the Spline Tool allows you to create them.


Select the Spline Tool in the or use keyboard the shortcut Alt+b to enable it. To leave that mode just select another from the toolbox.

It is easy to use this tool

  • Each single click creates a new Vertex. Its Tangent values are set to (0,0) and the Vertex becomes a sharp corner.
  • Click and drag creates a new Vertex and allows the modification of the Tangent value at that Vertex. Extending the Tangent smooths the corners.
  • Each new Vertex is attached to the previous by a Bézier Spline defined by the vertices’ position and tangents.
  • The Spline is created sequentially, one Vertex follows the previous one.
  • The end point of the previous Spline arc guides the next arc created until you close it. The next created Spline will be independent of the previously created one.
  • You can tweak the newly created Vertices by clicking on their handles and dragging them.
  • You can also right click on a Vertex handle or a Tangent handle and it will provide a context menu:
    • For Tangent handles: Split Tangent's Angle and Split Tangent's Radius will split the Tangent so that you can independently modify the arch of an end point of a Bézier curve. On the opposite, Merge Tangent's Angle and Merge Tangent's Radius will merge the independent Tangents so that you can align the arches of the end points of two connecting Bézier curves.
    • For Vertex handles: Loop Spline or Unloop Spline (depending if already looped or not) allows you to close or open the Spline. Delete Vertex allows you to delete the Vertex.
  • You can also right click in the middle of a Bézier curve. Insert Vertex allows the insertion of a Vertex (and sets its Tangents intelligently according to the neighboring Vertices) where you clicked.

To finish the Spline

  1. Select another tool in the .
  2. Or click on the gear button Gear_icon.png of the Tool Options Panel.

To clear out the working Spline, press the Esc button.




This tool has the following options:

  • Name: Sets the name of the Spline that you will create, in this case “Spline070”. If the ending part of the string contains an integer number, this input text box will parse it and increase that number for the next created Spline. Otherwise, it will add a three digit number while creating the next one.
  • Layer Type: Sets whether to create Region, Outline, Advanced Outline, Plant and/or Curve Gradient Layers.
  • Blend Method: Sets the blending method used to composite on the layers below.
  • Opacity: Sets the Amount Parameter for new layers. Defaults to 1.00 (Completely opaque).
  • Brush Size: Sets the size of the line for Outline Layer and/or Advanced Outline Layer.
  • Feather: Sets the feather parameter of the Region or Outline Layer created.
  • Link Origin: If checked, links the Origin Parameter for the Plant, Region or Outline if two of them (or all them) are checked.
  • Auto Export: If checked, exports automatically the Vertices parameter (that’s a Spline type parameter)

Other sources of information

See this video tutorial to see it in action.

Read Doc:Creating Shapes which talks a little about the Spline tool.

Read Dev:Spline_Bline about tangent internals computation.

Read Dev:Bline_Speed which explains about variations in the Amount parameter of Splines.

Category:Toolbox tool Category:Toolbox