The clock transformation is an angular fisheye transformation which allows a selected azimuthal region to be shown in detail while still displaying the full 360°. It is only available in the Y/X projection ( 5.1 Y/X Projection).
Under a clock transformation about an axis φ 0, φ transforms to φ new with:
φnew = φ0 + ((π/d)×Δφ) / ((π/d)+π-|Δφ|)
where d is the clock distortion factor and Δφ=φ-φ 0. The clock transformation does not change ρ. The values of X new, Y new are calculated from ρ and φ new.
Applying the Clock Transformation
The clock interaction is selected for the current canvas pad by clicking on the Clock tab of the interaction control ( 3.1.3. Interaction Control) in the Control Window. The label of the tab contains a toggle to activate and deactivate the interaction. Upon activation the distortion factor d is modified by clicking on a point at a selected opening angle with respect to the φ 0 direction and dragging it to a larger or smaller opening angle.
When the clock interaction is selected, a white line appears over the picture representing the selected φ 0 direction around which to perform the angular fisheye. This φ axis may be rotated by dragging it with the mouse.