Centre-based radial selection

Question

I have heard of a selection tool [probably] known as "radial selection". The user clicks somewhere ("the centre") and the selection area will be a circle whose radius is the distance between the cursor and the centre.

For example, in the image above, the user clicked CENTER and dragged his mouse to MOUSE CURSOR. The yellow area is the selection area, the red dots are selected while the green ones are not selected.

I tried to search on the internet but couldn't find any article or research paper dealing with this kind of selection method. What are the pros and cons about such a selection tool over regular selection tools (rectangular or elliptical selection tools for example). Are there any research papers covering this tool?

This question is about selection tools, not about menus.

Answer 1

Conventional rectangular or elliptical selection tools are good, when a user knows WHICH objects should be selected in advance. So, applaying these tools he:

• mentally builds appropriate selection area, which encloses all the needed objects,
• mentally defines starting selection point,
• physically selects the objects.

Radial selection is good for the objects, which have some (spatial) relations. Geo-based operations is one example. Heat transfer around heat-emmiting element is another.

Using circular selection tool a user knows HOW objects should be selected, or selection rules in other words. So he might not know which concrete objects should be selected in advance. The sequence is:

• mentally defines selection rule, which includes central point and end point constraints,
• physically selects the objects.

So fundamentail difference in data essense (as DA01 said), because data is a part of subject field which requires some specific operations (selection, etc.). This point allows to consider selection in context, as functional part within some field. This leads to understanding, the selection tools are different just because of subject fiels specificity.

Answer 2

The selection by proximity is not a strange tool, it's actually quite common in geo-based applications or map applications.

Not only traffic operators even automated systems use this type of selection to find the nearest camera to a car accident.

You can find extensive information sites on the GIS world.

Answer 3

To answer the question directly, it will depend entirely on what you are selecting.

If there is a need for encapsulating selected items as a circle, then having this as an option is an obvious pro.

If your items tend to be more grid-based (ala the icons on your desktop) then the circle selection probably doesn't make much sense as it's not useful for spanning specific columns or rows.

As such, I don't know really if there going to be any type of broad research on this given that it's so highly specific to the items being selected.

Answer 4

The main issue with this tool (in comparison with rectangular and elliptical selections) is that it sounds quite unusual. I'm arguing based on a personal experience basis. I use vector/raster graphic manipulations applications like twice a week (i.e. not that much, but still above the average), and never stumbled upon such a tool. It seems to me that it would be quite annoying for me to select stuff this way, mainly for a couple of drawbacks like

• drawing a circle starting from the center forces the user to spread the focus in all directions at the same time. The locus of attention, here, is clearly on the mouse pointer so, while I'm dragging the mouse, say, towards the bottom-right corner starting from the center, I have to pay attention to the circle expanding towards all directions to see what I'm actually selecting.
• it forces the selection to have a 1:1 aspect ratio, which is a kind of heavy constraint.

My assumption here is that the user knows what she wants to select (in terms of which elements, I mean).

A case in which this solution could be useful (but I have no proof on that) is the definition of a circular area in a geographic map (like "I want my AdWords campaign to target this city within this radius"), which actually would not be a selection task.

Answer 5

I think there are better ways of selecting features around an origin (btw. this process is called buffer):

• by selecting a point and specifying a buffer distance and unit, both could be pre-defined based on the need, e.g. 100 feet
• by selecting a point and specifying a time and distance, e.g. 5 minutes walking or 3 minutes driving
• by using a drawing tool different to what you have described, e.g. 'freehand lasso' or 'rectangle' - the radial selection is indeed atypical for a wide audience of users or even GIS users and text input as described above is probably always better.

Answer 6

Among other things these are called Radial Menus, Pie Menus... You may think you have never encountered one of these, but probably you have played some game that implemented a variation of it.

Pros

• Can be triggered anywhere and all options are near reach. This is very relevant to minimize input time. See Fitt's Law.
• After you have some training it becomes very easy to choose an option even when you don't have an input device that offers high precision, like the analog sticks on a console gamepad.

Cons

• These menus work well with few options. So if you need to have several options, you may lose some of the its benefits
• Depending on the input device, it might be difficult to choose an option
• These menus are not widespread, so you might have to implement them from scratch
• If you trigger it near a screen edge, you need to carefully consider how they will behave so that all options continue being displayed.

If you know some more cons, let me know. With these kinds of benefits I'm still trying to understand why there is not a widepread usage of these menus.

References

The Wikipedia entry. It contains some examples of software that implement these menus.
User Learning and Performance, by Buxton et al. This paper is old but it sure is not outdated. Also it has some references that you should check out.
It also seems that some Microsoft Office software has some radial menus. Wikipedia entry for Fitt's law is a bit dense. Consider reading this simpler explanation.