(Not) Knobs 1

So recently the topic of knobs came up on IRC again. Audio applications tend to have many semi-continuous parameters and knobs offer a way to fit them into little space.

The trouble with knobs is, that people can’t stick with one behaviour: some knobs have to be manipulated by click-hold and moving up and down or sideways (linear), while others react on direction (radial).

Radial has the advantage of allowing faster change or higher precision depending on how far away from center the pointer is moved. But moving the mouse in a circle is more of a hassle than a linear movement.

Linear movement is not intuitive with knobs. The shape and the metaphor both point to turning. It’s just simple in implementation and use.

Non-radial knobs should look differently. I had a go at that quite a while ago, but now want to be a little more systematic.

So let’s see what the realy important basic properties of knob-style widgets are and how they could behave.


  • Represent a parameter on rather small space, with a width/height ratio close to 1.
  • Allow changing the value via a click-drag operation
  • The point of reference should be the spot clicked on. The alternative would be the center of the widget, but having to aim for it to start from a neutral place is not acceptable.

What can be evaluated?

  • Distance from the center
    • Directly
    • Projected onto an axis
  • Direction
    • as fine-grained angle
    • in zones
  • Speed of pointer movement (tricky)

Each of these could be mapped either directly to the amount the value is changed, or to the rate of change (time based).
3 mouse buttons and 3 modifier keys allow many options and alternative modes.


About thorwil
I'm a designer from Germany. My main interests are visual and interaction design, free/open-source software and (electronic) music.

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