
Eigen defines several typedef shortcuts for most common aligned box types.
The general patterns are the following:
AlignedBoxSizeType where Size can be 1, 2,3,4 for fixed size boxes or X for dynamic size, and where Type can be i for integer, f for float, d for double.
For example, AlignedBox3d is a fixed-size 3x3 aligned box type of doubles, and AlignedBoxXf is a dynamic-size aligned box of floats.