A simplified version of the algorithm is below:

• Set i = index of closest target (T_i) by intersecting distance
• Set j = index of second closest target (T_j) by intersecting distance
• Set radius of bubble cursor = min(ConD_i, IntD_j)

This algorithm ensures that the bubble cursor will at least intersect the closest object, and possibly completely contain it. When the bubble only intersects the closest object and does not completely contain it, we morph the cursor by extending a second bubble, which quickly expands from the intersection points and envelopes the object. This acts as a reinforcing visual cue to the user that the object is indeed captured by the cursor.

 

In this task you need to implement an application with Python. The interface is illustrated in figure 4 below. The red object is the target to be selected. The grey objects are distractors. Note that the dotted lines, the letters and the arrow lines are not shown on the experimental interface. Users need to click the start button and then select the target. W Target D Start button L W Distractor Figure 4. Illustration of the application interface. (Click to expand the image) [Image transcript] Target and distractor size (W) should be set as 40 pixels in diameter. Targets and distractors are circular objects. They have the same size (see figure 4 above). Target distance (D) is the distance between the centre of the start button to the target. Target distance (D) is set as 512 pixels. There are 20 distractors and one target on the interface. Distractors will be presented randomly in the window. Distractors and the target should not overlap.