Octant (geometry)

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The three coordinate planes ( x = 0, y = 0, z = 0) divide the space into eight octants. They are identified by the eight cube-corner coordinates of the shape (±, ±, ±). In the horizontal coordinate plane you can see the four quadrants between the x and y axes. (The numbering of the points is balanced ternary with the smallest digit on the left, i.e. little-endian .)

In geometry , three-dimensional space is broken down into 8 parts by the coordinate planes of a Cartesian coordinate system , which are called octants . Since the limiting coordinate planes usually do not belong to any octant, the respective signs of the coordinates of a point in three-dimensional space indicate in which of the eight octants a point is located.

numbering

The octant of the three axes is positive (analogously to the first quadrant ) as the first designated. But there is no convention for numbering the other octants.

The following table shows the signed tuples together with possible numbering. A binary numbering with - as 1 can easily be generalized to different dimensions. A binary numbering with + as 1 defines the same order as a balanced ternary . The Roman numbering of the quadrants puts the pairs of signs in Gray-Code order. Therefore the corresponding order is also in the table of octants.

Octants
Gray
code
x y z Binary Bal.
ternary
- as 1 + than 1
< > < > < >
0 + + + 0 0 7th 7th 13 13
1 - + + 1 4th 6th 3 11 −5
3 + - + 2 2 5 5 7th 7th
2 - - + 3 6th 4th 1 5 −11
7th + + - 4th 1 3 6th −5 11
6th - + - 5 5 2 2 −7 −7
4th + - - 6th 3 1 4th −11 5
5 - - - 7th 7th 0 0 −13 −13
Quadrants for comparison
Rom. x y Binary Bal.
ternary
- as 1 + than 1
< > < > < >
I. + + 0 0 3 3 4th 4th
II - + 1 2 2 1 2 −2
IV + - 2 1 1 2 −2 2
III - - 3 3 0 0 −4 −4


Little and big endian are denoted by "<" and ">".

Octants in two-dimensional space

Occasionally two-dimensional space is also divided into octants. The four quadrants are divided on the straight lines and . The octants defined in this way are numbered counterclockwise from I to VIII, starting with the lower half of the first quadrant.

See also