# Voronoi pole

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In geometry, the positive and negative Voronoi poles of a cell in a Voronoi diagram are certain vertices of the diagram.

## Definition

Let ${\displaystyle V_{p}}$ be the Voronoi cell of the site ${\displaystyle p\in P}$. If ${\displaystyle V_{p}}$ is bounded then its positive pole is the Voronoi vertex in ${\displaystyle V_{p}}$ with maximal distance to the sample point ${\displaystyle p}$. Furthermore, let ${\displaystyle {\bar {u}}}$ be the vector from ${\displaystyle p}$ to the positive pole. If the cell is unbounded, then a positive pole is not defined, and ${\displaystyle {\bar {u}}}$ is defined to be a vector in the average direction of all unbounded Voronoi edges of the cell.

The negative pole is the Voronoi vertex ${\displaystyle v}$ in ${\displaystyle V_{p}}$ with the largest distance to ${\displaystyle p}$ such that the vector ${\displaystyle {\bar {u}}}$ and the vector from ${\displaystyle p}$ to ${\displaystyle v}$ make an angle larger than ${\displaystyle {\frac {\pi }{2}}}$.

## Example

Here ${\displaystyle x}$ is the positive pole of ${\displaystyle V_{p}}$ and ${\displaystyle y}$ its negative. As the cell corresponding to ${\displaystyle q}$ is unbounded only the negative pole ${\displaystyle z}$ exists.

## References

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