Drawing with Spiro
Spiro is a toolkit for designing curves in an alternate method to the more traditional Bézier
curves. Although it is optional, FontForge can be installed to include a Spiro mode that offers you
tools to create this specific kind of curves.
See “Installing FontForge” for more details on how to include the Spiro library in your program.
Spiro drawing has a different approach, that can help you getting your curves done in a different way and solving your conception problems. Please experiment!
The Spiro toolset
Many of the same drawing tools are available in Spiro mode as those described in the “Using the FontForge drawing tools” chapter, but some of them work very differently when you are in Spiro mode.
There are five different types of Spiro points:
- G4 points, used for a more gentle curve
- G2 points, used for a sharper curve
- Corner points, for abrupt corner joints
- Previous constraint points, used when the contour of the path changes from a curve to a straight line
- Next constraint points, used when the path changes from a straight line to a curve
Drawing an ‘S’ with Spiro
Going through the exercise of drawing an ‘S’ with Spiro will make you comfortable with Spiro.
Tip: When drawing in Spiro mode, always start with a G4 or G2 point. Beginning with the other types of points doesn’t really work in FontForge.
Start off with a G4 point at the topmost point of your ‘S,’ followed by a corner point, then another corner point. Work clockwise around the shape of the letter.
Follow this with a G4, a previous constraint point, and a next constraint point.
Next, add another G4 point, followed by two more corner points.
Then a G4, followed by a previous constraint, followed by a next constraint.
Then, add one more G4 point, and finally, close the shape at the starting point by clicking on it using the G4 point tool.
Now you almost have an ‘S’! Begin nudging the points around to get your S to look the way you want.
Oops, what happened?
Don’t worry — Spiro sometimes does some funny things. Just hit Undo, or keep nudging the points to get things back on track.
Now, you should see something like this:
Toggle out of Spiro mode back into Bézier mode. You will notice there are a lot of points on the resulting curve — you may want to clean some of them up.
To clean up those extra points, go to the Element menu and select Simplify > Simplify. Then go to Element > Add Extrema. Finally, go to Element > Round > To Int. After these clean up operations, you will see something like this:
You can continue to experiment with Spiro mode to get a feel of how it differs from Bézier
The terminology is different, but as with FontForge’s other drawing and adjustment tools, practice will get you the things you want.