1. Spiral splines in typeface design
A case study of Manjari Malayalam typeface
Hello & Welcome. I am Kavya, he is santhosh. We are going to discuss the use of Spiral spline curves in the design of typefaces, with Manjari - Malayalam typeface as an example. Santhosh did the design part and we together did the opentype engineering.
Santhosh Thottingal & Kavya Manohar
Swathanthra Malayalam Computing

2. This is a sample of Manjari typeface in 3 variants
This is a sample of Manjari typeface in 3 variants. It reads Manjari in Malayalam. Manjari has three variants - Bold, Regular and Thin. The curves in Manjari follow a spiral shaped path between its control points.. The terminals are also rounded, giving a very soft feeling for the eyes.

3. Here is another sample.
Contemporary style of Malayalam script is characterised by loops and curly strokes. Manjari follows this trend. But this was not the case during the early days of script evolution.

4. Vattezhuthu - Tharisappalli Copper plate 849 AD -9th centuary
Vattezhuthu - Tharisappalli Copper plate 849 AD -9th centuary. They were rather elongated curves or slightly rectangular.

5. 1772 Cleamant Pianius. The first printed book in Malayalam using movable types- Samkshepavedartham uses rectangular types.

6. 1829 - New testament - Benchamin Bailey - start of rounded types

7. Modern printing. 2018. Still rounded.

8. A good handwriting is when it is “rounded”
Manjari takes up this roundeness characteristics to the next level of perfection using spiral curve segments.

9. Optimal Curve
What defines an optimal rounded curve between two control points, especially in type design?

10. From spiral to splines - Optimal Techniques in interactive curve design Ralph Linus Levien
The answer was sought by Ralph Linus Levien on his thesis

11. Disjoing curves. No continuity
In typedesign curves are interpolated from control points. How smooth can be the joining of two different curve segments?
Let us see In what all different ways can two curve segments join together. This is a set of disjoint curves.
Disjoing curves. No continuity

12. G0 continuous curves. Continuous with abrupt transition
G0, continous, but not smooth. Has an abrupt transition.
G0 continuous curves. Continuous with abrupt transition

13. G1 continuous curves has common tangent
Here the join point is smoother with the tangents on either side of the curves being essentially the same. Call it G1 continuity.
G1 continuous curves has common tangent

14. G2 continuous curves has common center of curvature
The joining can be still more smooth, if it has a common centre of curvature at the joint points. This is G2 continuous joining of curve points.
G2 continuous curves has common center of curvature

15. in a two parameter, G2 continuous interpolating spiral spline
Every curve segment
in a two parameter, G2 continuous interpolating spiral spline
can be cut from an Euler spiral
G2 continuous interpolating spiral spline between adjacent control points can be cut from an Euler spiral subjecting to rotation, scaling, translation and mirror image transformations. He calls Euler spiral as the generating curve for spiral splines.

16. G2 continuous interpolating spiral spline between adjacent control points can be cut from an Euler spiral subjecting to rotation, scaling, translation and mirror image transformations}. He calls Euler spiral as the generating curve for spiral splines.

17. Spiral Spline
Every curve segment in the glyph is a segment from Euler spiral
G2 continuous interpolating spiral spline between adjacent control points can be cut from an Euler spiral subjecting to rotation, scaling, translation and mirror image transformations. He calls Euler spiral as the generating curve for spiral splines.

18. Design Process

19. Inkscape & Fontforge

25. Popularity

30. Manjari: github.com/smc/manjari