Tool: Curvature and Smooth
Here is a question that sounds naive and isn’t: why should you have to think about handles at all?
When you picture a curve, you don’t picture its tangents. You picture the places it goes. It comes down from up there, swings through about here, and ends over there. That’s the thought. The bezier handle is not in the thought — it’s an implementation detail of how the computer stores the curve, and the pen tool makes you type it in.
Curvature is the tool that takes the thought instead. You click the places the curve should pass through, and a smooth curve appears that passes through them. The handles get computed for you, and they get computed well: each anchor’s tangent is chosen so the curve flows continuously into its neighbours, which is the thing you were going to spend two minutes nudging by hand and get slightly wrong.
Click, click, click. Three points, one graceful curve through all three. Move any point afterwards and the curve reflows, still smooth, because the constraint is maintained rather than baked in.
This is a small tool and it is a good illustration of a principle I’d defend anywhere: the interface should accept the shape of the intention, not the shape of the storage format. The document stores beziers because beziers are what renders efficiently and what SVG understands. That’s the machine’s business. It is not a reason to make a person think in tangents when they were thinking in places. [1]
Smooth is the same idea, aimed at a curve that already exists and is ugly.
Freehand paths — anything from the pencil, anything from a trackpad, anything drawn by a hand that was in a hurry — come out lumpy. Not wrong, exactly: they pass through roughly the right places. But they carry the tremor of the hand that made them, encoded as thirty anchors where three would do, each one a little divot. Zoom in and the elegant arc you thought you drew is a staircase of tiny mistakes.
Drag Smooth along that path and it relaxes. Anchors get removed, tangents get reconciled, the tremor comes out, and the shape you meant is left behind. You can go over the same stretch again for more, so the strength of the effect is controlled by how much you use it, which is the right control because you can see the result while you’re deciding. [2]
The thing I like about both tools is that they are honest about the pen being hard. A lot of software would take the position that the pen is the professional tool, that professionals learn it, and that anyone who wants something easier can have a rounded-rectangle button and be grateful. That attitude confuses the difficulty of a tool with the seriousness of its user.
The pen is still there. It’s still the primitive, and when you need to place one anchor with one exact tangent, nothing else will do. But needing that is rarer than the pen’s prominence suggests, and for the ordinary case — I want a curve that goes through here, here, and here — being made to think in levers is just a tax. Curvature does not make you a lesser draughtsman. It makes you a faster one.
Every tool in this toolbar that isn’t the pen exists to keep you out of the pen.
[1] You can watch this same mistake being made all over software. A form asks for your date of birth in three dropdowns because the database has three columns. The database’s schema is not your problem, and a program that makes it your problem has confused its convenience for yours.
[2] There is a version of Smooth that takes a tolerance parameter and applies it to the whole path at once, and it is worse, because now you are guessing at a number and then evaluating the result, instead of just rubbing the part of the line that looks wrong until it stops looking wrong.