Manual: add hexagon pictures

### Hexagonal Pixels

Hexagonal pixel grids in Allpix Squared use an axial coordinate system to describe the relative positions and indices of

hexagons on the grid, following largely the definitions provided in \[[@hexagon]\]. Similar to the Cartesian coordinate

hexagons on the grid, following largely the definitions provided in \[[@hexagons]\]. Similar to the Cartesian coordinate

system used for regular pixel layouts, the origin is the lower-left corner of the sensor, with the hexagon indices $`(0,0)`$.

Owing to the orientation of the grid axes, negative can occur in the top-left region of the sensor.

For example, an 8-by-4 grid comprises 32 pixels both for *pointy* and *flat* hexagon orientation, but results in different

overall grid dimensions as demonstrated below:

![]()\

![](./hexagon_grids.png)\

*Grid layouts for pointy (left) and flat (right) hexagons with a size of 8-by-4 pixels.*