Antialiasing Parameter
From Synfig Studio :: Documentation
The Antialiasing parameter is a boolean parameter that activate the antialiased render of the shape (region, outline, etc.) what makes the edge of the shape to not be crisped against the background. When unchecked the antialiasing effect disappear and the shape is rendered more crisped.
Antialiasing ON
Antialiasing OFF
Antialiasing parameter panel