Pie Menu Design

Theta Menus Proposal and Pie Menu Designs - May 1986

On April 13, 1986, Mike Gallaher and I were brainstorming about Emacs and user interface design, and we came up with the following idea, which seemed worth writing down and persuing:

Clicking some sequence, say, double-right, lays down a help diagram showing what each direction of the mouse does. Moving outside the diagram exits this mode and removes the diagram. While in that mode, single clicks on the mouse keys cycle through the menu when the cursor is in the neutral area. Clicking while cursor is in one of the item's sectors selects that item.

menu is laid out so that all choices are initially equidistant from the cursor, so only direction is needed to choose one. The diagram stays as long as the button is held, while the cursor moves within it. The selection is indicated by the sector in which the cursor lies when the mouse button is released.

The output of the selection is the direction, perhaps


mouse menu for inputting numbers from circular scale (say, degrees).

time: press left to set hour hand, middle to set minute hand.

I described the idea to Mark Weiser, my undergraduate advisor at the University of Maryland, and he encouraged me to write it up, implement the idea, and empirically evaluate it.

To: hcil@mimsy.umd.edu
Cc: don@mimsy.umd.edu
Subject: circular menus
Date: Mon, 19 May 86 09:49:51 -0500
From: Mark Weiser <mark@markssun.cs.umd.edu>

A student of mine is thinking of building circular popup menus into the Sun window system. Here is his description of them.

Note particularly what happens if you follow a menu tree using these menus-- you get a shape on the screen which represents the path you followed. Experts remember long paths by muscle memory ("zig-zag-zig-zig-zag") instead of symbolically ("hjjkhj").

I don't know of anything similar. Anyone else? Other comments?

Date: Sun, 18 May 86 21:50:27 EDT
From: Don Hopkins <don@brillig.umd.edu>
To: mark@brillig.umd.edu
Subject: Theta Menus

Here are some preliminary notes and ideas...

Theta Menus

Menu selection is based on the angle between the mouse down event and the mouse up event. The radius should not have any bearing on which menu item is selected, and could even be used as an argument to the item.

The advantage is that if the user is familiar with the menu, no visual feedback is required to select an item. Just the direction has to be known. There is no need to slow the mouse down and "park" in in a small rectangle as with conventional pull down menus. If the user is familiar with the menu, then no visual attention at all is necessary. Thus you can be looking at something in one window while traversing menus in another. Pull down menus require that you move in the same direction every time you choose them (thus discarding theta), and depend on how far you move the mouse (depending on the radius instead). With pull down menus, there is no advantage to having fewer menu items, because you need just as precise control to choose each item.

Dynamic Pie Menus

The pie menus in The Sims are context sensitive, and hide inappropriate items, but the context depends on the state of the object and the selected user, so there are many different contexts which change dynamically over time.

So part of the game is figuring out how to manipulate the objects and people into the right state to enable the menu items you want.

Since The Sims game design requires that the menu items do change over time, that trumps the rule of thumb that pie menus should be used for static menus. User interface design involves weighing conflicting rules and making trade-offs according to the application and user requirements, so it's ok to break a few rules for good reasons.

An inactive TV set just has a "Turn On" menu item. When you activate it, the "Turn On" item disappears and is replaced by a bunch of items like "Turn Off", "Watch TV", "Change Channel," etc.

If you click on another Sim character, you get a menu of interpersonal interactions that the currently selected Sim can perform with the other Sim you clicked on. Those can change according to their relationships and moods.

Pie Menus are Better than Screen Corners

Pie menus address many of the complaints of this slashdot article, and they've been around a long time.

I'll start by comparing screen corners to pie menus:

To quote Tog on Fitts' Law: "The time to acquire a target is a function of the distance to and size of the target." He points out that "the screen edge is, for all practical purposes, infinitely deep."

But the advantage of "screen corners" is just an indirect and wasteful application of Fitts' Law, which pie menus exploit much more directly, efficiently and flexibly than "screen corners". Tog's "screen corner" argument is just an ex post facto application of Fitts' Law: an after-the-fact rationalization, not the reason they originally designed the menu bar that way. If Fitts' Law was really the reason Apple designed their menu bar that way, then why aren't there four menu bars, one at each edge of the screen? Apple never mentioned Fitts' Law in their infamous menu bar patent.

Pie menus "slices" are better than "screen corners" or "menu bars" because:

XML Pie Menus

Chris, a computer science student from digipen.edu who's interested in user interface design, asked me some interesting questions about pie menus:

First, were you happy with The Sims' implementation of pie menus? It seems as though it doesn't necessarily provide all of the great features of an ideal pie. The targets aren't infinitely 'deep' -- the user needs to click directly on the button. Perhaps more importantly, the targets aren't in predictable locations (they items are dynamic based on a very complex set of inputs.) Don't misunderstand; I loved the game and felt the the interface worked well. I am interested in the design decisions that were made.

The other thing I wanted ato ask was, have you any opinions on the game Sacrifice? I was very drawn to its pie system, and am always surprised that there has really never been much mention of it when it comes to discussion of pies, and pies in games. Thank you for your time,


Thanks for your thoughtful questions!

I'm glad to hear fasteroids still works after all those internet explorer patches that have come out since I wrote it. I hope the Eloas patent doesn't force Microsoft to break browser plug-ins like fasteroids and pie menus on purpose.

I'm pretty happy with the way The Sims pie menus turned out, considering the time and design constraints. But of course there are several things about them I would change and extend if I had the time.

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