Eye shape, Eye space - Discussion
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Old, short discussion below. See also the Eyes Collection of pages.
Eye space is a property of a group which is transformable into eyes. In practice, eyespace can be terrain almost or entirely surrounded by the group or it can be terrain adjacent to the group which can be made into eyes.
Examples of the former are given in most tsumego problems, which often consist of reducing and destroying the opponent's eyespace.
Examples of the latter are often used to describe connections. E.g. the trumpet connection is rich in eyespace.
There is a thin line betwen the concept of eyespace, eyeshape and 'potential for eyes' - they reflect the fact that it is not just the amount of territory available which decides actual eyes possible, but also the shape of that territory.
See also nakade.
-- Morten Pahle
(I like to think) I use the terms in a distinctly different sense.
- Eyespace is the space available for making eyes.
- Eyeshape is the (quality of) shape with respect to the goal of making eyes.
- Eye potential could be defined as the likelihood for making eyes, and increases as the eyespace is larger and the eyeshape better.
You can reduce eyespace, by playing a hane for example.
You can destroy eyeshape, by playing on the vital point.
But other people might use the terms differently.
Since the eyes of a group can be found at different ends of a group, I'm inclined to stick with my earlier attempt "the (quality of) the shape a group has, with respect to the goal of making eyes".
Otherwise said, I wouldn't think of eyeshape as being a property of the eyespace, but rather of the group. A group can have plenty of eyespace or almost no eyespace, but still have good or bad eyeshape according to the disposition of the stones.
Not sure though.
-- Dieter
Maybe we could use 'eye potential' as a 'larger' term, which encompasses both the shape and the size of the area(s) where eye(s) can be made? (Not sure either)
-- Morten Pahle
That is exactly what I have defined 'eye potential' to be earlier on. -- Dieter
The white group has lots of eyespace. But this space is also large enough for Black to build a living group, or at least a group with sufficiently good eyeshape to annoy White. #:-7
We cannot say that White's eyeshape is very good. The group consists of two straight lines.
In this example, White has much better eyeshape, though the property of White's eyespace in the corner hasn't changed. Stated more accurately: White has now two eyespaces, one already being an eye, and one where it will be easy to make a second one.
This white chain is out into the open. It has an enormous amount eyepace. Eyes can be made anywhere.
This group has available the same amount of eyespace, but has much better shape. The group will find it easier to make eyes, although the available eyespace is the same. As for the shape of the configuration, I'd rather say the shape of the group has changed, than the shape of the eyespace (although a change in the group composition, affects the composition of the eyespace and the other way round).
In this example, the Black stones make a nice shape. Without the marked white stones, the eyespace available is so vast that Black needn't worry about life.
With the marked stones present, the eyespace is greatly reduced, and now Black doesn't feel that comfortable anymore. A move at a, for example, could become annoying.
Eye potential for me is the combination of the space available to make eyes (eyespace) and the shape of the group with respect to the objective of making eyes (eyeshape).
I agree that in tsumego, where there is usually one group surrounded by another, eyeshape, eyespace and eye potential are virtually synonyms.
Linguisticly they can't be synonyms. You can't reduce eyeshape or destroy eyespace. Well, the latter probably is possible, strictly speaking. (Sorry for being so exhaustive.)
-- Dieter
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