Spline Tool

ALT-B

Introduction

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

Usage

Select the "Spline Tool" in the Toolbox Panel or use keyboard the shortcut AltB to enable it. To leave that mode just select another tool 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 Toolbox Panel.
2. Or click on the gear button of the Tool Options Panel.

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

Options

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 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 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 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.