Outline Layer

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Layer geometry outline icon.png

About Outline Layers

Outline Layers are use to hold strokes or edges of filled shapes. They give a cartoon look to an animation when added to be the edge of the filled shapes. Also standalone Outlines (strokes) are used to define fold of 3D drawings and used together with shadows (created using gradients or feathering) are the basis of an artist's work.

To create an Outline Layer use the BLine Tool and check Create Outline BLine in the Tool Options Panel. Once you finish the definition of the geometry of your outline and after pressing the Execute button (or selecting another tool or state) you create the Outline Layer with the current foreground colour.

Parameters of Outline Layers

The parameters of the Outline layers are:

Name Value Type
Type real icon.png Z Depth 0.000000 real
Type real icon.png Amount 1.000000 real
Type integer icon.png Blend Method Composite integer
Type color icon.png Color
Type vector icon.png Origin 0.000000u,0.000000u vector
Type bool icon.png Invert
Type bool icon.png Antialiasing
Type real icon.png Feather 0.000000pt real
Type integer icon.png Type of Feather Fast Gaussian Blur integer
Type integer icon.png Winding Style Non Zero integer
Type list icon.png Vertices List list (BLine)
Type real icon.png Outline Width 2.000000pt real
Type real icon.png Expand 0.000000pt real
Type bool icon.png Sharp Cusps
Type bool icon.png Rounded Begin
Type bool icon.png Rounded End
Type real icon.png Loopyness 1.000000 real
Type bool icon.png Homogeneous

Specific parameters for Outline Layers

The first 11 parameters of the Outline are common parameter that are shared for several types of Layers. Click on the links to see their definitions. Only the particular parameters for the Outline Layer are described here.

This is a sample screen shot of an Outline Layer in action:


Outline width

The Outline width parameter is a float value in pixels that represents the basic value of the width for all the points of the curve at the same time. It works together with the width parameter of the vertices' child values. So setting the Outline Width to 1.0px then the resulting value for the rendered width in that vertex comes from this formula: W = OLW * VW + 2E.


  • W = resulting width of the outline at that vertex.
  • OLW = overall parameter for the width of all the vertices (that is the Outline Width parameter).
  • VW = specific vertex width value.
  • E = value of the Expand parameter.

The width duck would show the radius value for that vertex (W/2).

The width that ends up being used for each vertex is ((VertexWidth * OutLineWidth) + Expand*2):

Image:Outline-default.png Image:Outline-outline-width.png
starting image after doubling the value of 'outline width'

It's possible to specify negative values for the width values, which kind of turns the vertex inside out. Here's an example where the left vertex has a negative width and the right has a positive width. Note how the edges of the bline between the vertices cross each other in the middle:

Image:Outline-negative-width.png Image:Outline-negative-width-selected.png


The Expand parameter is similar to the Outline Width parameter, but rather than being multiplied by each vertex's width, it is added to the radius of each vertex. In other words (2*Expand) is added to the diameter of each vertex.

The width that ends up being used for each vertex is ((VertexWidth * OutLineWidth) + Expand*2):

Image:Outline-default.png Image:Outline-expand.png
zero 'expand' non-zero 'expand'

Sharp cups

Enabling 'sharp cusps' makes the corners pointy when the tangents are split:

Image:Outline-default.png Image:Outline-sharp-cusps.png
no sharp cusps sharp cusps

Rounded Begin

Enabling 'rounded begin' makes the start of the outline rounded:

Image:Outline-default.png Image:Outline-rounded-begin.png
no rounded begin rounded begin

Rounded End

Enabling 'rounded end' makes the end of the outline rounded:

Image:Outline-default.png Image:Outline-rounded-end.png
no rounded end rounded end


This parameter currently does absolutely nothing at all!


Enabling 'Homogeneous' changes the way that the width of the outline changes from one blinepoint to the next. Each point in the bline has its own width, and the bline has its own 'Outline Width' and 'Expand' parameters which are used to give the final width at each blinepoint. The 'Homogeneous' parameter controls how the width is interpolated between two neighbouring blinepoints:

  • When 'Homogeneous' isn't checked, the width is interpolated linearly with the spline's 't' parameter.
  • When 'Homogeneous' is checked, the width is interpolated linearly with the spline's length.

Turning off homogeneous often makes the fat end of a bline look lumpy. Maybe that's a bug:

Image:Outline-not-homogeneous.png Image:Outline-homogeneous.png
not homogeneous homogeneous


The 'antialias' checkbox isn't specific to the Outline layer, but it is particularly useful for the Outline layer. It makes the edges appear smoother:

Image:Outline-no-antialias.png Image:Outline-default.png
not antialiased antialiased

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